deepmolecularresponseinchronicmyeloidleukemia:the new goal...

Review

DeepMolecular Response in ChronicMyeloid Leukemia: TheNew Goal of Therapy?

Francois-Xavier Mahon1 and Gabriel Etienne2

AbstractChronic myeloid leukemia (CML) is caused by formation of the BCR–ABL1 fusion protein. Tyrosine

kinase inhibitors (TKI) that target BCR–ABL1 are now the standard of care for patients with CML.

Molecular monitoring of residual BCR–ABL1 mRNA transcripts, typically performed using real-time

quantitative PCR, has improved treatment management, particularly for patients with CML in chronic

phase. Major molecular response (MMR; i.e., a �3-log reduction in BCR–ABL1 transcript levels) is used

in current treatment guidelines to assess prognosis. Recent evidence suggests that deeper molecular

responses (�4-log reductions in BCR–ABL1 transcript levels), particularly when attained early during

treatment, may have even better correlation with long-term outcomes, including survival and disease

progression. Furthermore, achieving deep molecular response is a requirement for entering trials

evaluating treatment-free remission (TFR). In this review, we discuss the evolving definition of minimal

residual disease and the various levels of molecular response under evaluation in current clinical studies.

In addition, the available clinical data on achieving MMR and deeper levels of molecular response with

TKI therapy, the prognostic value of deep molecular response, and factors that may predict a patient’s

ability to achieve and sustain a deep molecular response on TKI therapy are also discussed. Available

data from TFR studies are addressed. We discuss current knowledge of the ideal conditions for

attempting treatment discontinuation, factors predictive of molecular relapse, when TKI therapy should

be restarted, and which therapeutic strategies (when administered in the first-line setting and beyond)

are expected to best enable successful TFR. Clin Cancer Res; 20(2); 310–22. �2013 AACR.

IntroductionDysregulated protein tyrosine kinase (PTK) activity is

the hallmark of multiple neoplasms (1). Over the pastdecade, a broad array of drugs designed to selectively inhibitPTKs [i.e., tyrosine kinase inhibitors, (TKI)] have emerged asnovel therapies for patientswith cancer (2). Perhaps themostwell-knownPTK target todate is theBCR–ABL1oncoprotein,which is critical to the pathogenesis of chronic myeloidleukemia (CML; ref. 3). The successful treatment of patientswith CML with the BCR–ABL1 TKI imatinib has definitivelyvalidated this therapeutic strategy and established CML asa model disease for targeted cancer treatment (4).

With over a decade of imatinib use as first-line therapy inpatients withCML, surrogatemarkers that strongly correlatewith prognosis have been identified (5). The validation ofsurrogate endpoints for treatment effectiveness, such ascomplete hematologic response (CHR) and complete cyto-genetic response (CCyR), has improved treatment manage-ment (6, 7). Most patients, particularly those with CML inchronic phase (CML-CP), will achieve these endpoints on aBCR–ABL1 TKI (8–10). The progress of molecular biologyhas presented the opportunity to look beyond CHR andCCyR and monitor residual disease on a molecular level(11, 12). Current clinical practice recommendations forCML advocate monitoring patients for hematologicresponse (i.e., blood counts returning to normal values),cytogenetic response (i.e., disappearance of the Philadel-phia chromosome), andmolecular response (i.e., reductionin BCR–ABL1 gene expression; refs. 6 and 7). Molecularmonitoring is typically performed using real-time quanti-tative PCR (RQ-PCR), a simple technique that can beperformed on peripheral blood samples and is both moresensitive and more convenient than conventional cytoge-netics (13). The first level of response evaluated on themolecular scale, a major molecular response (MMR), cor-responds to a 3-log reduction in BCR–ABL1 transcript levelsfrom a standardized baseline (�0.1% BCR–ABL1 on theInternational Scale [BCR–ABL1IS]; refs. 11 and 14). MMR

Authors' Affiliations: 1Laboratoire d'H�ematologie, Centre Hospitalier Uni-versitaire de Bordeaux and Laboratoire H�ematopoï�ese Leuc�emique etCible Th�erapeutique, Bioth�erapies des maladies g�en�etiques et cancers,Inserm U1035, Universit�e Bordeaux S�egalen; and 2Centre R�egional deLutte Contre le Cancer de Bordeaux et du Sud-Ouest, Institut Bergoni�e,D�epartement d'Oncologie M�edicale, Bordeaux, France

Corresponding Author: Francois-Xavier Mahon, Laboratoire d'H�emato-logie, CHU de Bordeaux and Laboratoire H�ematopoï�ese normale et patho-logique, Universit�e Victor S�egalen Bordeaux 2, 146 rue L�eo-Saignat, InsermU1035, 33076BordeauxCedex, France. Phone: 33-5-5757-1524; Fax: 33-5-5693-8883; E-mail: [email protected]

doi: 10.1158/1078-0432.CCR-13-1988

�2013 American Association for Cancer Research.

ClinicalCancer

Research

Clin Cancer Res; 20(2) January 15, 2014310

Research. on September 11, 2018. © 2014 American Association for Cancerclincancerres.aacrjournals.org Downloaded from

Published OnlineFirst October 28, 2013; DOI: 10.1158/1078-0432.CCR-13-1988

http://clincancerres.aacrjournals.org/

hasbeen found tobe associatedwith improvedprogression-free survival (PFS; refs. 15 and 16) and event-free survival(EFS; refs. 17–19), although its prognostic value is stilldebated.The European LeukemiaNet (ELN) defines response to

TKI therapy based onmolecular and cytogenetic milestonesachieved at 3, 6, and 12 months, or beyond (6). The ELNrecommends evaluating molecular response using buffycoat from peripheral blood every 3 months until MMR isachieved, and then every 3 to 6 months. Cytogeneticresponse should be assessed using bone marrow at 3, 6,and 12 months, and then every 12 months once CCyR isachieved. Some patients (e.g., patients with monosomy 7,del[7q] or clonal chromosomal abnormalities)may requireadditional long-term bone marrow follow-up.Until recently, deepmolecular responses beyond the level

of MMR have remained largely unexplored, given a lack ofstandardized assay techniques (20). Several recent studieshave demonstrated that some patients with such responsescan achieve treatment-free remission (TFR), thereby chal-lenging the dogma that CML cannot be cured withoutallogeneic bone marrow transplantation (21, 22). Theoverall goals of therapy in CML—disease remission,reduced risk of progression, and improved overall survival(OS)—are clear; however, many questions remain aboutthe impact of molecular response on achieving these goals.Recent data, to be discussed herein, suggest that in selectpopulations, obtaining a deep molecular response shouldbe considered a primary therapeutic goal.

The Challenge of Defining Deep MolecularResponse

The development of the International Scale for BCR–ABL1 RQ-PCR assessment has enabled quantification ofmolecular response in relation to a standardized baseline(14, 23). The definition of MMR as BCR–ABL1IS �0.1%originates from the International Randomized Study ofInterferon Versus STI571 (IRIS; ref. 15). However, standard-ization of deeper levels of molecular response has provenless straightforward and is urgently needed to facilitateimproved interpretation of clinical results. Deeper levelsof molecular response may also be defined according to theInternational Scale, wherein MR4 indicates �4.0-logreduction (BCR–ABL1IS�0.01%),MR4.5 indicates�4.5-logreduction (BCR–ABL1IS �0.0032%), and MR5 indicates�5.0-log reduction (BCR–ABL1IS� 0.001%; Fig. 1; ref. 11).However, the observation of undetectable BCR–ABL1 tran-scripts is inherently linked to the sensitivity of the PCRmethod, as well as the control gene, used. An ongoingEuropean Treatment and Outcome Study (EUTOS) collab-oration aims to facilitate standardization of deepmolecularresponse across laboratories by establishing recommenda-tions for response definitions and quality control (11).

Varying definitions of complete molecular response(CMR) have been reported. For example, the NationalComprehensive Cancer Network (7) defines CMR as "nodetectable BCR–ABL1 chimeric mRNA as assessed by RQ-PCR using the International Scale with a sensitivity of 4.5-

CCR Reviews

© 2013 American Association for Cancer Research

100

10 1

2

3

4

4.5

5

6

1

0.1

0.01

0.0032

0.001

0.0001

BCR–ABL1(%IS)

Logreduction inBCR–ABL1

Reduction in BCR–ABL1

1:10

Baseline

ApproximatesMCyR

ApproximatesCCyR

MMR

Level of response

Deepmolecularresponse

MR6 (with currently available technology,this level of response cannot be assessed)

MR4

MR4.5

MR5

1:100

1:1,000

1:10,000

1:32,000

1:100,000

1:1,000,000

Figure 1. Levels of molecularresponse in CML. MCyR, majorcytogenetic response; MR,molecular response.

Deep Molecular Response in Chronic Myeloid Leukemia

www.aacrjournals.org Clin Cancer Res; 20(2) January 15, 2014 311




log reduction or more from the standardized baseline,"whereas the ELN (6) recommends using the term "molec-ularly undetectable leukemia" instead of "CMR" and notesthe importance of specifying control gene copy numberwhen reporting this level of response. Undetectable mini-mal residual disease indicates a negative RQ-PCR result andmust be associated with a defined PCR assay sensitivity;however, leukemic cellsmay still be present even if RQ-PCRresults are negative (24). Notably, current RQ-PCR meth-odology is largely optimized for detection of so-called"typical" BCR–ABL1 transcripts, or those involving themajor breakpoint cluster region, and may fail to detectatypical transcripts derived from other breakpoints (25);thus, assessment of transcript type at baseline is essential toensure accurate interpretation of RQ-PCR results.

Deep Molecular Response in Clinical Trials ofCML-CP

Deep molecular responses have been assessed in mul-tiple ongoing clinical trials of TKIs in patients with newlydiagnosed CML-CP (Table 1). Given the current lack ofstandardization of PCR sensitivity, rates of CMR reportedin these studies are not necessarily comparable. Discre-pancies in rates of deep molecular response may alsoresult from differences in assay techniques or studydesign. For example, PCR may be assessed using bloodor bone marrow, and response may be defined by a PCRresult at a single time point or confirmed by multiplesamples. Other variables include the study population(e.g., the proportion of high-risk patients), median fol-low-up at time of analysis, and type and dose of TKItherapy received. Although several studies have shownthat imatinib can elicit deep molecular responses in somepatients, second-generation TKIs, such as nilotinib anddasatinib, have demonstrated higher rates of deep molec-ular response attained within shorter time periods(Table 1). The combination of TKI therapy with interfer-on (IFN), which may help drive leukemic stem cells (LSC)into the cell cycle (26), thereby inducing deep molecularresponse, has also been explored. Rates of deep molecularresponse were higher with this combination versus ima-tinib alone in one study using pegylated IFN (26), butsimilar in another study using IFN-a (Table 1; ref. 27).

The Clinical Relevance of Deep MolecularResponse

Defining the value of achieving deep molecularresponse in patients with CML is an active area of ongoingresearch. There is conflicting evidence about whetherachieving an MMR provides additional benefit beyonda CCyR (20). The leukemic cell burden is similar inpatients with MMR and CCyR (only 1-log difference inBCR–ABL1 levels), and this difference may be too small toimpact long-term outcomes such as PFS and OS. Eventslike progression or death are quite infrequent with front-line TKI therapy; therefore, long-term follow-up and large

cohorts of patients would be required to definitivelydemonstrate any added benefit to achieving MMR.

However, deeper molecular responses provide moreseparation from CCyR in terms of residual disease bur-den; therefore, it may be easier to distinguish the uniquebenefits of such responses. Patients who achieve deepmolecular response seem less likely to lose MMR, andseveral studies have shown that deep molecular responsescorrelate with better long-term clinical outcomes, such asEFS, PFS, and OS, and a low risk of progression anddisease relapse (Table 2; refs. 28 and 29). For example, astudy by Etienne and colleagues (30) found that EFS andPFS were longer in patients with CMR than those withCCyR, regardless of MMR status; OS was not significantlydifferent between these groups. Another study by Falchiand colleagues (31) showed that patients with undetect-able BCR-ABL1 levels by 18 or 24 months had 100% ratesof OS, EFS, and transformation-free survival (TFS) at 6years. In the German CML study IV, life expectancy inpatients with MR4 or MR4.5 was the same as that in an age-matched population, and only 4 of 792 patients (0.5%)who achieved MR4 had disease progression (32).

These results provide encouraging evidence that achieve-ment of deep molecular response is an important clinicalgoal and prompt the question: should patients with CCyR,who donot achieve these deep levels ofmolecular response,be switched to an alternate therapy? Theongoing EvaluatingNilotinib Efficacy and Safety in Clinical Trials–CMR(ENESTcmr) study aims to address this question by ran-domizing patients with detectable BCR–ABL1 transcriptsafter�2 years on imatinib to either continue on imatinib orswitch to nilotinib (33). After 12 and 24 months of follow-up, more patients achieved MR4.5 and undetectable BCR–ABL1 (�4.5-log RQ-PCR assay sensitivity) on nilotinibcompared with continued imatinib (33). Yet perhaps themost convincing reason to strive for sustained deep molec-ular response in patients with CML-CP is the possibility thatit may enable eventual achievement of TFR.

Deep Molecular Response and TFRReports of imatinib discontinuation in patients without

sustained deep molecular responses have shown high andrapid rates of disease relapse (34–37). In contrast, a smallpilot study of imatinib discontinuation with the stringententry criteria of sustained CMR for �2 years on imatinibshowed promising results, with 6 of 12 patients remainingin molecular remission after a median 18 months of fol-low-up (38). This proof of concept inspired numerousclinical studies of imatinib discontinuation in patients withstable, deep molecular responses on TKI therapy (Table 3).In all cases, many patients were able to remain relapse-freeoff therapy.

Importantly, molecular relapse, the trigger for reintro-duction of TKI therapy in these studies, was often defineddifferently. For example, in the Stop Imatinib (STIM) study,molecular relapse was defined as positive RQ-PCR resultson 2 consecutive assessments (39, 40), whereas in the STIM

Mahon and Etienne

Clin Cancer Res; 20(2) January 15, 2014 Clinical Cancer Research312




Tab

le1.

Clinicaltrialsof

TKIthe

rapyreportin

gdee

pmolec

ular

resp

onse

s(M

R4or

dee

per)o

ccurrin

ginpatientswith

newlydiagn

osed

CML-CP

Trial

Sam

ples,

na

Ass

ayse

nsitivity

(ISstan

dardized

?)Med

ian

f/u,

mo

Treatmen

t!MR

endpoints

asse

ssed

IRIS

(15,

24)

1�4

.5logs

(estab

lishe

dtheIS)

25IM

400mgqd(n

¼33

3)!

CMRat

12mo¼

4%b

81IM

400mgqd(n

¼29

c)!

MR4/M

R4.5by81

mo¼

70%

/52%

.MR4.5at

81mo¼

45%

ID-01_

151(66)

1�5

logs

(No)

15IM

400mgb.i.d.(n¼

112)

!CMR¼

28%

deLa

vallade

etal.(67

)�2

cons

ecutive

NR(Yes

)38

IM40

0mgqd(n

¼20

4d)!

CMR¼

5%

RIG

HT(68)

1�4

.5logs

(Noe)

17f

IM40

0mgb.i.d.(n¼

115)

!CMRby6,

12,1

8mo¼

39%

,44%

,55%

Verma

etal.(29

)1

�4.5

logs

(NR)

65IM

400mgqd(n

¼73

)or80

0mgqd(n

¼20

8)!

CMR¼

44%

SPIRIT

(26)

1g(Yes

)47

hIM

400mgqd(n

¼15

9)!

MR4at

12,2

4mo¼

14%

,21%

.CMRat

24mo¼

9%IM

400mgqdþ

AraC

(n¼

158)

!MR4at

12,2

4mo¼

15%

,26%

.CMRat

24mo¼

8%IM

400mgqdþPEG-IFN

(n¼15

9)!

MR4at

12,2

4mo¼30

%,3

8%.C

MRat

24mo¼16

%IM

600mgqd(n

¼16

0)!

MR4at

12,2

4mo¼

17%

,26%

.CMRat

24mo¼

8%

CMLStudyIV

(27)

1NR(Yes

)43

IM40

0mgqd(n

¼32

4)!

MR4by

12,2

4,36

mo¼

8%,3

1%,4

6%48

IM40

0mgqdþ

IFN-a

(n¼

350)

!MR4by12

,24,

36mo¼

12%

,30%

,41%

28IM

800mgqd(n

¼33

8)!

MR4by

12,2

4,36

mo¼

20%

,43%

,57%

ENESTn

d(10)

1i (Y

es)

Min

36NIL

300mgb.i.d.(n¼

282)

!MR4by1,

3y¼

20%

,50%

.MR4.5by1,

3y¼

11%

,32%

NIL

400mgb.i.d.(n¼

281)

!MR4by1,

3y¼

15%

,44%

.MR4.5by1,

3y¼

7%,2

8%IM

400mgqd(n

¼28

3)!

MR4by

1,3y¼

6%,2

6%.M

R4.5by1,

3y¼

1%,1

5%

ENEST1

st(69)

1NR(Yes

)6.5f

NIL

300mgb.i.d.(n¼

205)

!MR4by3,

6mo¼

5%,2

0%

GIM

EMA(70,

71)

1;stab

le,

3�

4moap

art

�4logs

(Yes

)48

NIL

400mgb.i.d.(n¼

73)!

MR4at

12,2

4,36

mo¼

12%

,27%

,25%

51NIL

400mgb.i.d.(n¼

73)!

Stable

MR4¼

25%

MDACC

NIL

pha

seII(72)

1�5

logs

(Yes

)17

.3NIL

400mgb.i.d.(n¼

51)!

CMRby6,

12,3

0mo¼

4%,1

1%,1

5%

Nicolini

etal.(73

)1

NR(Yes

)13

.6NIL

300mgb.i.d.þ

PEG-IFN

(n¼

40)!

MR4at

6,12

,15mo¼

23%

,57%

,80%

.MR4.5at

6,12

,15mo¼

10%

,21%

,50%

.MR5at

6,12

,15mo¼

10%

,15%

,40%

DASISION

(9)

1NR(Yes

)Min

24DAS10

0mgqd

(n¼

259)

!MR4.5by2y¼

17%

IM40

0mgqd(n

¼26

0)!

MR4.5by2y¼

8%

(Con

tinue

don

thefollo

wingpag

e)






Tab

le1.

Clinical

trials

ofTK

Ithe

rapyreportin

gdee

pmolec

ular

resp

onse

s(M

R4or

dee

per)o

ccurrin

gin

patientswith

newly

diagn

osed

CML-

CP

(Con

t'd)

Trial

Sam

ples,

na

Ass

ayse

nsitivity

(ISstan

dardized

?)Med

ian

f/u,

mo

Treatmen

t!MR

endpoints

asse

ssed

S03

25(74)

1NR(j )

36DAS10

0mgqd(n

¼99

)!MR4/M

R4.5at

1y¼

27%

/21%

IM40

0mgqd

(n¼

91)!

MR4/M

R4.5at

1y¼

21%

/15%

MDACC

DAS

pha

seII(75)

1�5

logs

(Yes

)24

DAS10

0mgqdor

50mgb.i.d

.(n¼

50)!

CMRat

6,12

,30mo¼

0%,7

%,0

%

BELA

(76)

1�4

logs

(Yes

)13

.8f

BOS50

0mgqd(n

¼25

0)!

MR4at

12mo¼

12%

IM40

0mgqd

(n¼

252)

!MR4at

12mo¼

3%

Abbreviations

:AraC,c

ytarab

ine;

BELA

,Bos

utinib

Effica

cyan

dSafetyinChron

icMye

loid

Leuk

emia;b

.i.d.,tw

icedaily;B

OS,b

osutinib;D

AS,d

asatinib;D

ASISION,D

asatinib

Versu

sIm

atinibStudyinTrea

tmen

t-Naive

CMLpa

tients;ENEST1

st,E

valuatingNilo

tinibEffica

cyan

dSafetyinClinicalTrialsas

First-Line

Trea

tmen

t;ENESTn

d,E

valuatingNilo

tinibEffica

cyan

dSafetyin

Clinical

Trials–New

lyDiagn

osed

Patients;

f/u,

follo

w-up;G

IMEMA,G

ruppo

Italiano

Malattie

Ematolog

iche

dell'A

dulto;IM,imatinib;IRIS,Interna

tiona

lRan

dom

ized

Interferon

Versu

sSTI57

1;IS,Interna

tiona

lSca

le;M

DACC,M

DAnd

erso

nCan

cerC

enter;min,m

inim

um;M

R,m

olec

ular

resp

onse

;NIL,n

ilotin

ib;N

R,n

otreported;q

d,d

aily;P

EG-IFN

,pe

gylatedinterferon

a-2a

;qd,o

ncedaily;R

IGHT,

Rationa

lean

dInsigh

tfor

Gleev

ecHigh-Dos

eTh

erap

y;SPIRIT,S

TI57

1Prosp

ectiv

eRan

dom

ized

Trial;SWOG,S

outhwes

tOnc

olog

yGroup

.aNum

ber

ofsa

mplesrequiredto

mee

tcrite

riaforresp

onse

.bPatientswith

CCyR

only.

cSub

grou

pan

alys

isof

patientsen

rolledin

theIRIS

stud

yin

Aus

tralia

andNew

Zea

land

from

June

2000

toFe

bruary20

07.

dNote:

17of

thes

epatientswerealso

intheIRIS

stud

y.eBas

elineBCR–ABL1

/ABL1

ratio

bas

edon

pres

tudysa

mplesfrom

partic

ipatinglaboratory.

f Med

ianex

posu

re.

g�2

5,00

0co

piesof

ABLwererequiredforasa

mple

tobeco

nsidered

adeq

uate.

hFo

rallp

atients;

48moforpatientsaliveas

ofdatacu

toff.

i �3,00

0co

piesof

ABLwererequiredforasa

mpleto

beco

nsidered

adeq

uate.

j Stand

ardized

toSWOG-spec

ificBCR–ABL1

bas

elineleve

l.

Mahon and Etienne





Tab

le2.

Clinical

outcom

esof

patientswith

newly

diagn

osed

CML-CPwho

achiev

eddee

pmolec

ular

resp

onse

swith

TKIthe

rapy

Outco

mes

forpatientswithorwitho

utdee

pmolecu

lar

resp

ons

e,%

Trial

des

criptio

nN

Med

ian

f/u,

mo

Comparators

EFS

rate

PFS

rate

OSrate

TFS

rate

Etie

nneet

al.(30

):first-lineIM

400mg

266

53.2

CCyR

þMMRþ

CMRa

CCyR

þMMR�

CMRa

CCyR

�MMR

95 65 28

98 82 56

OSwas

not

differen

tam

ong

the3grou

ps

NR

NR

NR

Falchi

etal.(31

):first-lineIM

(400

mg,

n¼

83;

800mg,

n¼

204),N

IL(n

¼10

6),

orDAS(n

¼10

2)

495

73NoMRat

18mo

MMRat

18mo

MR4at

18mo

MR4.5at

18mo

Und

etec

table

BCR-A

BLb

at18

mo

NoMRat

24mo

MMRat

24mo

MR4at

24mo

MR4.5at

24mo

78(6

y)94

(6y)

97(6

y)93

(6y)

100(6

y)80

(6y)

90(6

y)97

(6y)

95(6

y)

NR

NR

NR

NR

NR

NR

NR

NR

NR

93(6

y)98

(6y)

97(6

y)95

(6y)

100(6

y)92

(6y)

97(6

y)10

0(6

y)97

(6y)

90(6

y)10

0(6

y)10

0(6

y)10

0(6

y)10

0(6

y)90

(6y)

100(6

y)10

0(6

y)10

0(6

y)Und

etec

table

BCR-A

BLb

at24

mo

100(6

y)NR

100(6

y)10

0(6

y)

CMLstud

yIV

(32):fi

rst-lineIM

400mg,

IM40

0mgþ

IFN-a

,IM

400mgþ

AraC,IM

after

IFN-a

failure,o

rIM

800mg

1,52

567

.5After

amed

iandurationof

MR4of

3.7y,

only

4of

792patientswith

CMR4(0.5%)p

rogres

sed;life

expec

tanc

ywith

MR4an

dMR4.5was

iden

tical

tothat

oftheag

e-match

edpo

pulation

Kan

tarjian

etal.(28

):retros

pectivean

alysis.IM

(400

mg,

n¼

71;8

00mg,

n¼

205)

276

48Durab

leCMRb(�

6mo)

Non

durab

leCMRb(<6mo)

NR

NR

100(5

y)98

(5y)

NR

NR

NR

NR

Vermaet

al.(29

):retros

pec

tivean

alysis.F

irst-line

IM(400

mg,

n¼

73;8

00mg,

n¼

208)

281

65CCyR

þMMRþ

CMRbat

2y

CCyR

þMMR�

CMRbat

2y

CCyR

�MMR�

CMRbat

2y

100(5

y)96

(5y)

86(5

y)

NR

NR

NR

NR

NR

NR

100(5

y)96

(5y)

91(5

y)

Press

etal.(77

):all

patientsac

hiev

edCCyR

onIM

andha

d�2

mea

suremen

tsof

BCR–ABL1

leve

lafter

achiev

ing

CCyR

9049

MMRþ

CMRc

MMR�

CMRc

NR

NR

Not

reac

hedd

44mod

NR

NR

NR

NR

Abbreviations

:AraC,c

ytarab

ine;

DAS,d

asatinib;f/u,follow-up;IM,imatinib;M

R,m

olec

ular

resp

onse

;NIL,n

ilotin

ib;N

R,n

otreported.

aCMRwas

defi

nedas

undetec

table

BCR–ABL1

tran

scrip

tswith

ase

nsitivity

of�4

.5logs

on2co

nsec

utivean

alyses

�2moap

art.

bMinim

umse

nsitivity

4.5logs

.cMinim

umse

nsitivity

4logs

.dDatash

ownaremed

ianrelapse

-freesu

rvival,d

efine

das

progres

sion

toac

celeratedph

ase/blast

crisis,los

sof

complete

hematolog

icresp

onse

,orloss

ofCCyR

.






Table 3. Clinical trials of TKI discontinuation in patients with CML-CP and deep molecular response

TrialTreatment before d/c(response required for d/c) Definition of relapse

Relapse-free pts, %(medianf/u, mo)

Patients respondingto TKI after relapse

Trials of IM d/cSTIM (ref. 40; N ¼ 100) IM for�36 mo (MR5 for�24 mo) Confirmed loss of MR5 39% (30) 56/61 regained MR5

ALLG CML8/TWISTER(ref. 55; N ¼ 40)

IM for �36 mo (MR4.5 for�24 mo)

Confirmed loss ofMR4.5

45% (42) 22/22 regained MMRa

According to STIM(ref. 41; N ¼ 66)

IM for �36 mo (MR4.5 for�24 mo)

Loss of MMR 64% (23) 24/24 regained MMRa

Korean study (ref. 78;N ¼ 48)

IM for�36mo (CMR for�24mo) Confirmed loss ofMMR

81% (15.8) 8/9 regained MMRa

Yhim et al.(ref. 54; N ¼ 14)

IM for median 56.4 mo; range,26.2–82.0 (CMR for �12 mo)

Confirmed loss ofCMR

28.6% at12 mo (23)

7/10 regained CMR

Keio STIM (ref. 79;N ¼ 40)

IM for median 98 mo; range,24–126 (UMRDb for �24 mo)

Loss of UMRDb 55.4% at12 mo (15.5)

17/18 regained CMR

Takahashiet al.retrospective analysis(ref. 80; N ¼ 43)

IM for median 45.2 mo; range,4.5–92.7 [UMRD (�4-logsensitivity) by RQ-PCR,RT-PCR, or TMA]

Molecular recurrenceafter d/c of IM for�6 mo

56% (22.4) 17/17 regained MMRa

STIM 2c (ref. 57;N ¼ 200)

IM (MR5 for �2 y) Loss of MMR and/or>1-log increase inBCR–ABL1

Studyongoing

Study ongoing

Trials of NIL d/cNilo post-STIMc

(ref. 57; N ¼ 70)NIL for �2 y in patients whofailed TFR in STIM or STIM 2(confirmed CMR after 2 yof NIL)

Loss of MR5 on 2consecutiveassessments

Studyongoing

Study ongoing

ENESTFreedomc

(ref. 57; N ¼ 175)First-line NIL for�2 y and 1 y NILon study (MR4.5 for �1 y)

Loss of MMR Studyongoing

Study ongoing

ENESTopc (ref. 57;N ¼ 117)

TKI therapy for �3 y, including�2 y of second-line NIL and1 y NIL on study (MR4.5 for�1 y)

Confirmed loss of MR4

or any loss of MMRStudyongoing

Study ongoing

ENESTgoalc (ref. 57;N ¼ 300)

IM for �1 y and NIL on study(MR4.5 for 1 or 2 y)

Confirmed loss of MR4 Studyongoing

Study ongoing

ENESTPathc (ref. 57;N ¼ 1,058)

IM for �2 y and NIL on study(MR4 for 1 or 2 y)

Loss of MR4 Studyongoing

Study ongoing

TIGERc (ref. 57;N¼652) First-line NIL þ PEG-IFN-a vs.NIL for �2 y on study, thenPEG-IFN-a vs. NILmaintenance therapy(stable MR4)


Study ongoing

Trials of DAS d/cDASFREEd (57) (N ¼ 75) DAS for �2 y (MR4.5 for �1 y) Loss of MMR Study

ongoingStudy ongoing

Trials of TKI d/cSTOP 2G-TKI (ref. 42;N ¼ 34)

NIL or DAS for �36 mo (UMRDfor �24 mo, with �20,000ABL1 copies)

Loss of MMR 58.3% at12 mo (14)

13/15 regained MMR

10/13 regained CMR

EURO-SKId (ref. 57;N ¼ 500)

TKI therapy (first-line or second-line) for �3 y (MR4 for �1 y)


Study ongoing

(Continued on the following page)

Mahon and Etienne





study, molecular relapse was less stringently defined as lossof MMR at any time (41). In According to STIM, all 24patients who relapsed regained a response ofMMRor betteronce imatinib was reintroduced (41); therefore, waitinguntil a patient loses MMR to reinitiate TKI therapy doesnot seem to be detrimental. This suggests that BCR–ABL1positivity after TKI cessation does not necessarily equaldisease relapse (22). However, the optimal molecularresponse threshold for triggering restart of TKI therapyremains to be established.Data on discontinuation of second-generation TKIs are

limited; however, the ongoing STOP 2G-TKI study hasshown similar results to those of imatinib discontinuationtrials (Table 3; ref. 42). Thus, available results suggest thatstopping TKI therapy in patients with sustained deepmolec-ular response can be safe and associated with prolongedTFR. Given the preliminary nature of available clinical dataon TFR, both the ELN and the National ComprehensiveCancer Network currently recommend that patients remainon TKI therapy indefinitely and that TKI discontinuationonly be attempted in controlled clinical trials (6, 7).

Factors Affecting Achievement of DeepMolecular ResponseAchievement ofBCR–ABL1IS�10%at 3 or 6months after

initiating first-line imatinib has been shown to be predictiveof long-term molecular response and improved outcomes(19, 43, 44), whereas delayed cytogenetic and molecularresponse on imatinib is associated with increased risk ofprogression (45). Landmark studies of second-generationTKIs have found BCR–ABL1 levels at 3 months to besimilarly predictive (46, 47). A retrospective analysis of

patients treated with second-line nilotinib, dasatinib, orbosutinib found that BCR–ABL1IS �10% at 3 months fromstart of second-line treatment was associated with signifi-cantly higher cumulative incidence of MMR and CMR andimproved OS, PFS, and EFS (48). An online database ofpatients with CML-CP treated with first-line imatinib inJapan found that patients with an MMR at 12 months weresignificantly more likely than those without to achieveundetectable BCR–ABL1 transcripts by 72 months (49).Another study found a similar association in patients trea-ted with first-line or second-line imatinib (24).

Other factors that may affect achievement of deepmolec-ular response include risk score, sex, adherence to treat-ment, and dose intensity. For example, in the EvaluatingNilotinib Efficacy and Safety in Clinical Trials–Newly Diag-nosed Patients (ENESTnd) phase III trial of first-line nilo-tinib versus imatinib, rates of deepmolecular responsewerelowest among patients with high Sokal score, althoughmore high-risk patients achieved MR4.5 by 3 years onnilotinib than imatinib (24%, 27%, and 9% in the nilotinib300 mg b.i.d., nilotinib 400 mg b.i.d., and imatinib arms,respectively; ref. 10). Univariate analysis of a study inpatients treatedwith first-line imatinib showed that femaleswere more likely than males to achieve stable undetectableBCR–ABL1 (with a RQ-PCR sensitivity of �4.5 log) by 8years (68% vs. 30%, respectively; ref. 50). Multivariateanalysis of a study in Japanese patients found adherenceto standard-dose imatinib to be predictive of CMR achieve-ment (51). Another study reported adherence to standard-dose imatinib as the only independent predictor of CMR;poor adherence and failure to achieve MMR predictedtreatment discontinuation and eventual loss of CCyR(52, 53).

Table 3.Clinical trialsof TKIdiscontinuation inpatientswithCML-CPanddeepmolecular response (Cont'd )

TrialTreatment before d/c(response required for d/c) Definition of relapse

Relapse-free pts, %(medianf/u, mo)

Patients respondingto TKI after relapse

DESTINYd (ref. 57;N ¼ 168)

IM, NIL, or DAS for �3 y andhalf-standard dose of TKI for1 y on study (MMR or MR4 for�1 y at therapeutic dose and1 y at half-standard dose)


Study ongoing

NCT00573378c (ref.57; N ¼ 40)

NIL or IM for �3 y, with stabledose for �1 y and sameTKI þ PEG-IFN-a for 2 y onstudy (NR)

NR Studyongoing

Study ongoing

Abbreviations: ALLG, Australasian Leukaemia and LymphomaGroup; DAS, dasatinib; d/c, discontinuation; f/u, follow-up; IM, imatinib;MR, molecular response; NIL, nilotinib; NR, not reported; PEG-IFN-a, pegylated interferon-a; RT-PCR, nested reverse transcriptasePCR; TMA, transcription-mediated amplification; UMRD, undetectable minimal residual disease.aPatients achieved this level of response or better.bUMRD defined as <100 copies by TMA; thus, loss of UMRD was >100 copies by TMA.cCurrently recruiting participants.dNot yet recruiting participants.






Factors Affecting Durability of Deep MolecularResponse Off Treatment

The high rates of and rapidity of disease relapseobserved in patients who discontinue TKI therapy with-out deep molecular response (34–37) suggest that themain factor influencing relapse risk off therapy is the levelof residual molecular disease present when TKI therapy isstopped. However, even among patients with sustained,undetectable disease on TKI therapy, a significant per-centage of patients have experienced disease relapse (40),and several studies have evaluated factors potentiallycontributing to a patient’s ability to achieve successfulTFR.

Studies of imatinib discontinuation have found anassociation between Sokal score and relapse risk (39,40, 54, 55), suggesting that patients with high Sokal riskmay have inherent biologic attributes that drive develop-ment of disease relapse once BCR–ABL1 inhibition isrelieved. The duration of deep molecular response beforeTKI discontinuation and the overall duration of prior TKItreatment also seem to be important (39, 40, 56). Basedon this, the majority of ongoing studies require patientsto maintain a deep molecular response for �2 years andhave had �3 years of prior TKI treatment before attempt-ing discontinuation. More rapid achievement of deepmolecular response may also be predictive of successfulTFR (54, 55).

In the STIM study, the only factors associated withlower risk of relapse were low/intermediate Sokal scoreand duration of imatinib treatment >5 years (39, 40).Another study identified a subgroup of patients withincreased risk of molecular relapse following imatinibdiscontinuation, characterized by the following: highSokal score, >24 months to CMR, and <33 months ofimatinib after achieving CMR; patients with any of thesecharacteristics had a 0% probability of CMR persistenceat 1 year, compared with 80% probability in patientswithout these characteristics (54). Several other ongoingTKI discontinuation studies aim to determine other fac-tors that may play a role in relapse off treatment (Table3). For example, the large, phase III EURO-SKI study(NCT01596114) will explore factors associated withmolecular relapse in patients with stable MR4 who stopTKI therapy, and STIM 2 (NCT01343173) will evaluatefactors predictive of sustained deep molecular responseafter imatinib discontinuation (57). Current data suggestthat deep molecular response is heterogeneous, anddifferent patients may have differing levels of residualdisease burden despite having undetectable disease (22).

Most, if not all, patients with sustained CMR havepersistent BCR–ABL1-positive cells (based on PCR at aDNA level; ref. 55 and 58); however, this persistence doesnot necessarily lead to relapse after treatment discontinu-ation. Furthermore, the kinetics of relapse after treatmentdiscontinuation vary, with early and late molecularrelapses observed (39). This discrepancy may reflect theheterogeneity of CML at the stem cell level. The develop-

ment of highly sensitive techniques like ultra-deepsequencing (UDS) and massive parallel sequencing (MPS)may help clarify these differences. Indeed, both UDS andMPS detected more complex mutation dynamics in TKI-resistant patients than conventional Sanger sequencing(59, 60).

Mathematical modeling of the kinetics of molecularrelapse in patients in the STIM study has led to a hypothesisthat selective pressure exerted by imatinib treatment resultsin an increased frequency of LSC clones with slower growthand differentiation than the predominant clone at baseline(61). Imatinib therapy may affect the ability of LSCs toproduce differentiated populations and may affect the celldivision of progenitors and differentiated leukemic cells(61). The effects of imatinib on leukemia-initiating cells(LIC) may differ from patient to patient, and these differ-ences maymanifest in varying times tomolecular relapse inpatients with deep molecular response who stop imatinibtreatment (Fig. 2).

It remains to be established whether the ultimate goalof treatment for patients with CML-CP will be a "clinicalcure" (i.e., the absence of relapse) or a "biological cure"(i.e., absence of all leukemic cells, including LSCs;refs. 22, 62, 63). Multiple strategies for specifically tar-geting the LSC reservoir in patients with CML are underinvestigation, including combination of a BCR–ABL1 TKIwith other targeted agents, such as inhibitors of theHedgehog, Wnt/B-catenin, or Notch signaling pathways,or immunomodulatory agents, such as IFN (22, 62, 63).In one study, maintenance therapy with peglyated IFNfollowing imatinib discontinuation led to retained orimproved molecular responses in the majority ofpatients, most of whom did not have deep molecularresponses (64). This may represent a viable strategy forpatients who wish to stop TKI therapy in the absence ofdeep molecular response; the ongoing TIGER study isfurther investigating this approach (Table 3). Quantifi-cation of a patient’s residual LSC reservoir and the effectof such combination treatments on LSCs remains achallenge (22, 65). Given the potential diversity in dis-ease burden and relapse risk in patients who discontinueTKI therapy, rigorous long-term follow-up is essential,and discontinuation should only be attempted in clinicaltrials.

ConclusionsMolecular monitoring affords a precise, convenient

method for monitoring residual disease burden inpatients with CML-CP. As TKIs have improved patientoutcomes, clinical trial designs have begun to evaluatedeeper levels of molecular response. Deep molecularresponses are associated with improved rates of PFS, EFS,and OS, and reduced risk of progression to advanceddisease. Furthermore, a sustained deep molecularresponse is an essential entry criterion for studies of TFR.The ability to achieve deep molecular response on ther-apy, and sustain this response off therapy, may be

Mahon and Etienne





affected by a variety of factors, including disease char-acteristics, risk score, and adherence to and time ontreatment. As more is learned about the optimal criteriafor successful TKI discontinuation, patients may haveincreased chances of achieving treatment-free diseasecontrol, a first step toward the elusive cure for CML.

Disclosure of Potential Conflicts of InterestF.-X. Mahon has received commercial research grants from Bristol-Myers

Squibb and Novartis Pharma. F.-X. Mahon is a consultant/advisory boardmember of Bristol-Myers Squibb,Novartis Pharma, andAriad. G. Etienne is aconsultant/advisoryboardmemberof Bristol-Myers Squibb,Novartis, Pfizer,and Ariad.

Authors' ContributionsConception and design: F.-X. Mahon, G. EtienneDevelopment of methodology: F.-X. MahonWriting, review, and/or revision of themanuscript: F.-X. Mahon, G. Etienne

AcknowledgmentsThe authors thank K. Miller-Moslin, PhD, and P. Tuttle, PhD (Articulate

Science), for medical editorial assistance.

Grant SupportFinancial support formedical editorial assistance was provided byNovar-

tis Pharmaceuticals Corporation.

Received July 19, 2013; revisedOctober 8, 2013; acceptedOctober 9, 2013;published OnlineFirst October 22, 2013.

References1. Van Etten RA, Shannon KM. Focus onmyeloproliferative diseases and

myelodysplastic syndromes. Cancer Cell 2004;6:547–52.2. Natoli C, Perrucci B, Perrotti F, Falchi L, Iacobelli S, Consorzio

Interuniversitario Nazionale per Bio-Oncologia (CINBO).

CCR Reviews

© 2013 American Association for Cancer Research

LSCs

A

B

LICs Imatinib therapySTOP

STOP

LSCs LICs Imatinib therapy

LIC with intrinsicallyfaster growth rate

Sur

viva

l with

out

mo

lecu

lar

rela

pse

Months since discontinuation of imatinib

0.00 3 6 9 12 15 18 21 24 27 30 33

Stem cell persistence butundetectable using RQ-PCR

(5-log sensitivity)

Late molecular relapse

Early molecular relapse

36 39 42 45 48 51 54 57 60

0.10.20.30.40.50.60.70.80.91.0

LIC with intrinsicallyslower growth rate

Sur

viva

l with

out

mo

lecu

lar

rela

pse

Months since discontinuation of imatinib

0.00 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60

0.10.20.30.40.50.60.70.80.91.0

Figure 2. Hypothesis for variability in duration of deepmolecular response in patientswho discontinue imatinib. Imatinib treatment has differing effects on LICsthat introduce variability in times to molecular relapse after imatinib discontinuation. A, in some patients, imatinib treatment may successfully eradicate LICs,leaving only a small population of quiescent LSCs that is undetectable by conventional RQ-PCR (�5-log sensitivity), enabling prolonged TFR. B, in otherpatients, populations of LICs with variable growth kinetics remain. Patients with faster-growing residual LICs experience more rapid molecular relapse ondiscontinuation of imatinib treatment, whereas patients with slower-growing residual LICs experience later molecular relapse. Inset graphs show the Kaplan–Meier estimate of relapse-free survival in the STIM study (relapse defined as confirmed loss of molecular response �5-log reduction) based on a medianfollow-up of 30 months (40).






Tyrosine kinase inhibitors. Curr Cancer Drug Targets 2010;10:462–83.

3. DrukerBJ. Translationof thePhiladelphia chromosome into therapy forCML. Blood 2008;112:4808–17.

4. Melo JV, Barnes DJ. Chronic myeloid leukaemia as amodel of diseaseevolution in human cancer. Nat Rev Cancer 2007;7:441–53.

5. Hernandez-Boluda JC, Cervantes F. Prognostic factors inchronic myeloid leukaemia. Best Pract Res Clin Haematol 2009;22:343–53.

6. Baccarani M, Deininger MW, Rosti G, Hochhaus A, Soverini S,Apperley JF, et al. European LeukemiaNet recommendations forthe management of chronic myeloid leukemia: 2013. Blood 2013;122:872–84.

7. National Comprehensive Cancer Network. NCCN Clinical PracticeGuidelines in Oncology: Chronic Myelogenous Leukemia. Version4.2013. [cited 2013 Jul 12]. Available from: http://www.nccn.org/pro-fessionals/physician_gls/pdf/cml.pdf.

8. Deininger M, O'Brien SG, Guilhot F, Goldman JM, Hochhaus A,Hughes TP, et al. International randomized study of interferon vs.STI571 (IRIS) 8-year follow up: sustained survival and low risk forprogression or events in patients with newly diagnosed chronic mye-loid leukemia in chronic phase (CML-CP) treated with imatinib. Blood2009;114:462 (abstr 1126).

9. Kantarjian HM, Shah NP, Cortes JE, Baccarani M, Agarwal MB,Undurraga MS, et al. Dasatinib or imatinib in newly diagnosed chronicphase chronic myeloid leukemia: 2-year follow-up from a randomizedphase 3 trial (DASISION). Blood 2012;119:1123–9.

10. Larson RA, Hochhaus A, Hughes TP, Clark RE, Etienne G, Kim DW,et al. Nilotinib vs. imatinib in patients with newly diagnosed Philadel-phia chromosome-positive chronicmyeloid leukemia in chronicphase:ENESTnd 3-year follow-up. Leukemia 2012;26:2197–203.

11. Cross NCP, White H, M€uller MC, Saglio G, Hochhaus A. Standardizeddefinitions of molecular response in chronic myeloid leukemia. Leu-kemia 2012;26:2172–5.

12. Tibes R, Mesa RA. Evolution of clinical trial endpoints in chronicmyeloid leukemia: efficacious therapies require sensitive monitoringtechniques. Leuk Res 2012;36:664–71.

13. Cortes J, Quintas-Cardama A, Kantarjian HM. Monitoring molecularresponse in chronic myeloid leukemia. Cancer 2011;117:1113–22.

14. Hughes T, Deininger M, Hochhaus A, Branford S, Radich J, Kaeda J,et al. Monitoring CML patients responding to treatment with tyrosinekinase inhibitors: review and recommendations for harmonizing cur-rent methodology for detecting BCR-ABL transcripts and kinasedomain mutations and for expressing results. Blood 2006;108:28–37.

15. Hughes TP, Kaeda J, Branford S, Rudzki Z, Hochhaus A, Hensley ML,et al. Frequency ofmajormolecular responses to imatinib or interferon-aplus cytarabine in newly diagnosed chronicmyeloid leukemia. NEnglJ Med 2003;349:1423–32.

16. Press RD, Love Z, Tronnes AA, Yang R, Tran T, Mongoue-Tchokote S,et al. BCR-ABL mRNA levels at and after the time of a completecytogenetic response (CCR) predict the duration of CCR in imatinibmesylate-treated patients with CML. Blood 2006;107:4250–6.

17. Cortes J, Talpaz M, O'Brien S, Jones D, Luthra R, Shan J, et al.Molecular responses in patients with chronic myelogenous leukemiain chronic phase treated with imatinib mesylate. Clin Cancer Res2005;11:3425–32.

18. Pavlovsky C, Giere I, Moiraghi B, PavlovskyMA, Aranguren PN,GarciaJ, et al. Molecular monitoring of imatinib in chronic myeloid leukemiapatients in complete cytogenetic remission: does achievement of astable major molecular response at any time point identify a privilegedgroup of patients? Amulticenter experience in Argentina andUruguay.Clin Lymphoma Myeloma Leuk 2011;11:280–5.

19. Hughes TP, Hochhaus A, Branford S, Muller MC, Kaeda JS, Foroni L,et al. Long-termprognostic significance of earlymolecular response toimatinib in newly diagnosed chronic myeloid leukemia: an analysisfrom the International Randomized Study of Interferon Versus STI571(IRIS). Blood 2010;116:3758–65.

20. Breccia M, Alimena G. The significance of early, major and stablemolecular responses in chronic myeloid leukemia in the imatinib era.Crit Rev Oncol Hematol 2011;79:135–43.

21. Mahon FX. Is going for cure in chronic myeloid leukemia possible andjustifiable? Hematology Am Soc Hematol Educ Program 2012;2012:122–8.

22. Rea D, Rousselot P, Guilhot J, Guilhot F, Mahon FX. Curing chronicmyeloid leukemia. Curr Hematol Malig Rep 2012;7:103–8.

23. Branford S, Fletcher L, Cross NC, Muller MC, Hochhaus A, Kim DW,et al. Desirable performance characteristics for BCR-ABL measure-ment on an international reporting scale to allow consistent interpre-tation of individual patient response and comparison of response ratesbetween clinical trials. Blood 2008;112:3330–8.

24. Branford S, Seymour JF, Grigg A, Arthur C, Rudzki Z, Lynch K, et al.BCR-ABL messenger RNA levels continue to decline in patients withchronic phase chronic myeloid leukemia treated with imatinib for morethan 5years and approximately half of all first-line treated patients havestable undetectable BCR-ABL using strict sensitivity criteria. ClinCancer Res 2007;13:7080–5.

25. Burmeister T, Reinhardt R. A multiplex PCR for improved detection oftypical and atypical BCR-ABL fusion transcripts. Leuk Res 2008;32:579–85.

26. PreudhommeC, Guilhot J, Nicolini FE, Guerci-Bresler A, Rigal-HuguetF, Maloisel F, et al. Imatinib plus peginterferon a-2a in chronic myeloidleukemia. N Engl J Med 2010;363:2511–21.

27. Hehlmann R, Lauseker M, Jung-Munkwitz S, Leitner A, Muller MC,PletschN, et al. Tolerability-adapted imatinib 800mg/d versus 400mg/d versus 400 mg/d plus interferon-alpha in newly diagnosed chronicmyeloid leukemia. J Clin Oncol 2011;29:1634–42.

28. Kantarjian H, O'Brien S, Shan J, Huang X, Garcia-Manero G, Faderl S,et al. Cytogenetic and molecular responses and outcome in chronicmyelogenous leukemia: need for new response definitions? Cancer2008;112:837–45.

29. Verma D, Kantarjian HM, Shan J, O'Brien S, Verma A, Jabbour E, et al.Sustained completemolecular response to imatinib in chronicmyeloidleukemia (CML): a target worth aiming and achieving? Blood 2009;114(abstr 505).

30. Etienne G, Nicolini FE, Dulucq S, Schmitt A, Hayette S, Lippert E, et al.Achieving a complete molecular remission under imatinib therapy isassociated with a better outcome in chronic phase chronic myeloidleukaemia patients on imatinib frontline therapy. Blood 2012;120 (abstr3754).

31. Falchi L, Kantarjian HM, Quintas-Cardama A, O'Brien S, Jabbour EJ,Ravandi F, et al. Clinical significance of deeper molecular responseswith four modalities of tyrosine kinase inhibitors as frontline therapy forchronic myeloid leukemia. Blood 2012;120 (abstr 164).

32. HehlmannR, LausekerM,HanfsteinB,M€ullerMC, Schreiber A, ProetelU, et al. Complete molecular remission (CMR 4.5) of CML is inducedfaster by dose—optimized imatinib predicts better survival—resultsfrom the randomized CML-study IV. Blood 2012;120 (abstr 67).

33. Hughes TP, Lipton JH, Spector N, Leher B, Pasquini R, Clementino N,et al. Switching to nilotinib is associated with continued deepermolecular responses in CML-CP patients with minimal residual dis-ease after �2 years on imatinib: ENESTcmr 2-year follow-up results.Blood 2012;120 (abstr 694).

34. Cortes J, O'Brien S, Kantarjian H. Discontinuation of imatinib therapyafter achieving a molecular response. Blood 2004;104:2204–5.

35. Mauro MJ, Druker BJ, Maziarz RT. Divergent clinical outcome in twoCML patients who discontinued imatinib therapy after achieving amolecular remission. Leuk Res 2004;28(suppl 1):S71–3.

36. Merante S, Orlandi E, Bernasconi P, Calatroni S, Boni M, Lazzarino M.Outcome of four patients with chronic myeloid leukemia after imatinibmesylate discontinuation. Haematologica 2005;90:979–81.

37. Michor F, Hughes TP, Iwasa Y, Branford S, Shah NP, Sawyers CL,et al. Dynamics of chronic myeloid leukaemia. Nature 2005;435:1267–70.

38. Rousselot P, Huguet F, Rea D, Legros L, Cayuela JM, Maarek O, et al.Imatinib mesylate discontinuation in patients with chronic myeloge-nous leukemia in complete molecular remission for more than 2 years.Blood 2007;109:58–60.

39. Mahon FX, Rea D, Guilhot J, Guilhot F, Huguet F, Nicolini F, et al.Discontinuation of imatinib in patients with chronic myeloid leukaemiawho have maintained complete molecular remission for at least 2

Mahon and Etienne





years: the prospective, multicentre stop imatinib (STIM) trial. LancetOncol 2010;11:1029–35.

40. Mahon F, Rea D, Guilhot J, Guilhot F, Huguet F, Nicolini FE, et al.Discontinuation of imatinib in patients with chronic myeloid leukemiawho have maintained complete molecular response: update results ofthe STIM study. Blood 2011;118 (abstr 603).

41. Rousselot P, Charbonnier A, Cony-Makhoul P, Agape P, Nicolini F,Varet B, et al. Loss of major molecular response is accurate forrestarting imatinib after imatinib discontinuation in CP-CML patientswith long lasting CMR: importance of fluctuating values of MRD andinterferon. Haematologica 2012;97(s1):77 (abstr 194).

42. Rea D, Rousselot P, Guilhot F, Tulliez M, Nicolini FE, Guerci-Bresler A,et al. Discontinuation of second generation (2G) tyrosine kinase inhi-bitors (TKI) in chronic phase (CP)-chronic myeloid leukemia (CML)patients with stable undetectable BCR-ABL transcripts. Blood2012;120 (abstr 916).

43. Marin D, Hedgley C, Clark RE, Apperley J, Foroni L, Milojkovic D, et al.Predictive value of early molecular response in patients with chronicmyeloid leukemia treated with first-line dasatinib. Blood 2012;120:291–4.

44. HanfsteinB,MullerMC,HehlmannR, ErbenP, LausekerM, FabariusA,et al. Early molecular and cytogenetic response is predictive for long-term progression-free and overall survival in chronic myeloid leukemia(CML). Leukemia 2012;26:2096–102.

45. Quintas-Cardama A, Kantarjian H, Jones D, Shan J, Borthakur G,Thomas D, et al. Delayed achievement of cytogenetic and molecularresponse is associated with increased risk of progression amongpatients with chronic myeloid leukemia in early chronic phasereceiving high-dose or standard-dose imatinib therapy. Blood 2009;113:6315–21.

46. HochhausA,Guilhot F, Haifa Al-Ali K, Rosti G,NakasekoC, Antonio DeSouzaC, et al. EarlyBCR-ABL transcript levels predict futuremolecularresponse and long-term outcomes in newly diagnosed patients withCML-CP: analysis of ENESTnd 3-year data. Haematologica 2012;97(s1):237 (abstr 0584).

47. Hochhaus A, Boque C, Bradley Garelik MB, Manos G, Steegmann JL.Molecular response kinetics and BCR-ABL reductions in patients withnewly diagnosed chronicmyeloid leukemia in chronic phase (CML-CP)receiving dasatinib versus imatinib: DASISION 3-year follow-up. Hae-matologica 2012;97(s1):609 (abstr 1537).

48. Milojkovic D, Apperley JF, Gerrard G, Ibrahim AR, Szydlo R, Bua M,et al. Responses to second-line tyrosine kinase inhibitors are durable:an intention-to-treat analysis in chronic myeloid leukemia patients.Blood 2012;119:1838–43.

49. Tauchi T, Kizaki M, Okamoto S, Tanaka H, Tanimoto M, Inokuchi K,et al. Seven-year follow-up of patients receiving imatinib for thetreatment of newly diagnosed chronic myelogenous leukemia by theTARGET system. Leuk Res 2011;35:585–90.

50. Branford S, RossD, Prime J, FieldC, AltamuraH, YeomanA, et al. Earlymolecular response and female sex strongly predict achievement ofstable undetectable BCR–ABL1, a criterion for imatinib discontinua-tion in patients with CML. Blood 2012;120 (abstr 165).

51. Yoshida C, Komeno T, Hori M, Kimura T, Fujii M, Okoshi Y, et al.Adherence to the standard dose of imatinib, rather than dose adjust-ment based on its plasma concentration, is critical to achieve a deepmolecular response in patients with chronic myeloid leukemia. Int JHematol 2011;93:618–23.

52. Marin D, Bazeos A, Mahon FX, Eliasson L, Milojkovic D, Bua M, et al.Adherence is the critical factor for achieving molecular responses inpatients with chronic myeloid leukemia who achieve complete cyto-genetic responses on imatinib. J Clin Oncol 2010;28:2381–8.

53. Ibrahim AR, Eliasson L, Apperley JF, Milojkovic D, Bua M, Szydlo R,et al. Poor adherence is the main reason for loss of CCyR and imatinibfailure for chronic myeloid leukemia patients on long term therapy.Blood 2011;117:3733–6.

54. Yhim HY, Lee NR, Song EK, Yim CY, Jeon SY, Shin S, et al. Imatinibmesylate discontinuation in patients with chronic myeloid leukemiawho have received front-line imatinib mesylate therapy and achievedcomplete molecular response. Leuk Res 2012;36:689–93.

55. Ross DM, Branford S, Seymour JF, Schwarer AP, Arthur C, Yeung DT,et al. Safety and efficacy of imatinib cessation for CML patients withstable undetectableminimal residual disease:Results from theTWIST-ER study. Blood 2013;122:515–22.

56. Lee SE, Choi SY, Bang JH, Kim SH, Jang EJ, Choi M, et al. BCR-ABLkinetics after discontinuation of imatinib in CMLpatients withMR4.5 orundetectable molecular residual disease. Haematologica 2012;97(s1):80 (abstr 200).

57. U.S. National Institutes of Health. Clinicaltrials.gov. [cited 2013 Sept12]. Available from: http://www.clinicaltrials.gov/.

58. Ross DM, Branford S, Seymour JF, Schwarer AP, Arthur C, Bartley PA,et al. Patients with chronic myeloid leukemia whomaintain a completemolecular response after stopping imatinib treatment have evidence ofpersistent leukemia by DNA PCR. Leukemia 2010;10:1719–1724.

59. Eyal E, Tohami T, Amir A, Cesarkas K, Jacob-Hirsch J, Volchek Y, et al.Detection of BCR–ABL1 mutations in chronic myeloid leukaemia bymassive parallel sequencing. Br J Haematol 2013;160:477–86.

60. Soverini S, De Benedittis C, Machova Polakova K, Brouckova A,Horner D, IaconoM, et al. Unraveling the complexity of tyrosine kinaseinhibitor-resistant populations by ultra-deep sequencing of the BCR-ABL kinase domain. Blood 2013;122:1634–48.

61. Tang M, Foo J, Gonen M, Guilhot J, Mahon FX, Michor F. Selectionpressure exerted by imatinib therapy leads to disparate outcomes ofimatinib discontinuation trials. Haematologica 2012;97:1553–61.

62. Chomel JC, Turhan AG. Chronicmyeloid leukemia stem cells in the eraof targeted therapies: resistance, persistence and long-term dorman-cy. Oncotarget 2011;2:713–27.

63. Ross DM, Hughes TP, Melo JV. Do we have to kill the last CML cell?Leukemia 2011;25:193–200.

64. Burchert A, Muller MC, Kostrewa P, Erben P, Bostel T, Liebler S, et al.Sustained molecular response with interferon alfa maintenance afterinduction therapy with imatinib plus interferon alfa in patients withchronic myeloid leukemia. J Clin Oncol 2010;28:1429–35.

65. Chu S, McDonald T, Lin A, Chakraborty S, Huang Q, Snyder DS, et al.Persistence of leukemia stem cells in chronic myelogenous leukemiapatients in prolonged remission with imatinib treatment. Blood2011;118:5565–72.

66. Kantarjian H, Talpaz M, O'Brien S, Garcia-Manero G, Verstovsek S,Giles F, et al. High-dose imatinib mesylate therapy in newly diagnosedPhiladelphia chromosome-positive chronic phase chronic myeloidleukemia. Blood 2004;103:2873–8.

67. deLavalladeH,Apperley JF,KhorashadJS,MilojkovicD,ReidAG,BuaM, et al. Imatinib for newly diagnosed patients with chronic myeloidleukemia: incidence of sustained responses in an intention-to-treatanalysis. J Clin Oncol 2008;26:3358–63.

68. Cortes JE, Kantarjian HM, Goldberg SL, Powell BL, Giles FJ, WetzlerM, et al. High-dose imatinib in newly diagnosed chronic-phase chronicmyeloid leukemia: high rates of rapid cytogenetic and molecularresponses. J Clin Oncol 2009;27:4754–9.

69. Hochhaus A, Rosti G, le Coutre PD, Ossenkoppele G, Griskevicius L,Rea D, et al. ENEST1st: nilotinib in patients with newly diagnosedchronic myeloid leukemia in chronic phase (CML-CP): a European andEUTOS clinical initiative for standardization of molecular response.Haematologica 2012;97(s1):74 (abstr 0188).

70. Gugliotta G, Castagnetti F, Breccia M, Levato L, Capucci A, Tiribelli M,et al. Early CP CML, nilotinib 400 mg twice daily frontline: beyond 3years, results remain excellent and stable (A GIMEMA CML WorkingParty trial). Blood 2011;116 (abstr 2756).

71. Rosti G, Gugliotta G, Castagnetti F, Breccia M, Levato L, Rege-Cambrin G, et al. Five-year results of nilotinib 400 mg BID in earlychronic phase chronic myeloid leukemia (CML): high rate of deepmolecular response—update of the GIMEMACMLWP trial CML0307.Blood 2012;120 (abstr 3784).

72. Cortes JE, Jones D, O'Brien S, Jabbour E, Konopleva M, Ferrajoli A,et al. Nilotinib as front-line treatment for patients with chronic myeloidleukemia in early chronic phase. J Clin Oncol 2010;28:392–7.

73. Nicolini FE, Etienne G, Dubruille V, Roy L, Huguet F, Legros L, et al.Pegylated interferon-a2a incombination to nilotinib as first line therapyin newly diagnosed chronic phase chronic myelogenous leukemia






provides high rates of MR4.5. Preliminary results of a phase II study.Blood 2012;120 (suppl; abstr 166).

74. Radich JP, Kopecky KJ, Applebaum FR, Kamel-Reid S, Stock W,Malnassy G, et al. A randomized trial of dasatinib 100 mg vs imatinib400 mg in newly diagnosed chronic phase chromic myeloid leukemia.Blood 2012;120:3898–905.

75. Cortes JE, Jones D, O'Brien S, Jabbour E, Ravandi F, Koller C, et al.Results of dasatinib therapy in patients with early chronic-phasechronic myeloid leukemia. J Clin Oncol 2010;28:398–404.

76. Cortes JE, Kim DW, Kantarjian HM, Brummendorf TH, Dyagil I, Gris-kevicus L, et al. Bosutinib versus imatinib in newly diagnosed chronic-phase chronic myeloid leukemia: results from the BELA trial. J ClinOncol 2012;30:3486–92.

77. Press RD, Galderisi C, Yang R, Rempfer C, Willis SG, Mauro MJ,et al. A half-log increase in BCR-ABL RNA predicts a higher risk of

relapse in patients with chronic myeloid leukemia with an imatinib-induced complete cytogenetic response. Clin Cancer Res 2007;13:6136–43.

78. Lee S, Choi SY, Bang J, Kim S, Jang E, Byeun J, et al. Predictivefactors for successful imatinib cessation in chronic myeloidleukemia patients treated with imatinib. Am J Hematol 2013;88:449–54.

79. Matsuki E, Ono Y, Tonegawa K, Sakurai M, Kunimoto H, Ishizawa J,et al. Detailed investigation on characteristics of Japanese patientswith chronic phase CML who achieved a durable CMR after discon-tinuation of imatinib—an updated result of the Keio STIM study. Blood2012;120 (abstr 2788).

80. Takahashi N, Kyo T,Maeda Y, Sugihara T, Usuki K, Kawaguchi T, et al.Discontinuation of imatinib in Japanese patients with chronic myeloidleukemia. Haematologica 2012;97:903–6.

Mahon and Etienne





2014;20:310-322. Published OnlineFirst October 28, 2013.Clin Cancer Res François-Xavier Mahon and Gabriel Etienne Goal of Therapy?Deep Molecular Response in Chronic Myeloid Leukemia: The New

Updated version

10.1158/1078-0432.CCR-13-1988doi:

Access the most recent version of this article at:

Cited articles

http://clincancerres.aacrjournals.org/content/20/2/310.full#ref-list-1

This article cites 66 articles, 33 of which you can access for free at:

Citing articles

http://clincancerres.aacrjournals.org/content/20/2/310.full#related-urls

This article has been cited by 10 HighWire-hosted articles. Access the articles at:

E-mail alerts related to this article or journal.Sign up to receive free email-alerts

Subscriptions

Reprints and

[email protected]

To order reprints of this article or to subscribe to the journal, contact the AACR Publications Department at

Permissions

Rightslink site. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC)

.http://clincancerres.aacrjournals.org/content/20/2/310To request permission to re-use all or part of this article, use this link



http://clincancerres.aacrjournals.org/lookup/doi/10.1158/1078-0432.CCR-13-1988

http://clincancerres.aacrjournals.org/content/20/2/310.full#ref-list-1

http://clincancerres.aacrjournals.org/content/20/2/310.full#related-urls

http://clincancerres.aacrjournals.org/cgi/alerts

mailto:[email protected]

http://clincancerres.aacrjournals.org/content/20/2/310


deepmolecularresponseinchronicmyeloidleukemia:the new goal...

Documents