is low-dose aspirin use associated with a reduced risk of colorectal cancer ? a qresearch primary...
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Is low-dose Aspirin use associated with a reduced risk of colorectal cancer ? a QResearch primary care database analysis
Prof Richard Logan, Dr Yana Vinogradova, Dr Carol Coupland, Prof Julia Hippisley-Cox,Divisions of Primary Care, and Epidemiology & Public Health, University of Nottingham, UK
BSG Annual Meeting, Birmingham15th March 2011
Low-Dose Aspirin in the Primary
Prevention of Cancer(Cook et al. JAMA 2005)
Aspirin 50mg/day Placebo Rel Risk
Colon 103 / 111 0.92
Rectum 30 / 25 1.20
Colorectal 133 / 136 0.97 (0.77-1.24)
Average of 10 years of treatment
1
0
.25
.5
.75
1
1.25
1.5
1.75
1 2- 13-25-37-49+ 1 2- 13-25-37-49+ 1 2- 13-25-37-49+ 1 2- 13-25-37-49+
Statins COX-2 Inhibitors Traditional NSAIDs Aspirin
odds ratio compared to no prescriptions for a drug grouplower/upper limits of 95 percent confidence interval
Adj
uste
d O
dds
Rat
io
Number of scripts
© QRESEARCH 2005
Number of scripts in 13-96 months prior to the index date
Vinogradova et al. Gastroenterology 2007
1
0
.25
.5
.75
1
1.25
1.5
1.75
1 2-12 13-24 25+ 1 2-12 13-24 25+ 1 2-12 13-24 25+ 1 2-12 13-24 25+
Statins COX-2 Inhibitors Traditional NSAIDs Aspirin
odds ratio compared to no prescriptions for a drug grouplower/upper limits of 95 percent confidence interval
Adj
uste
d O
dds
Rat
io
Number of scripts
© QRESEARCH 2005
Number of scripts in 13-48 months prior to the index date
Vinogradova et al. Gastroenterology 2007
Study population: QRESEARCH database
• Currently largest primary care database in
the UK
• 574 general practices across the UK
• > 9 million patients including those who have
died or left, as well as patients still registered
• > 30 million person-years of observation
Data source: QRESEARCH database
• Derived from GP clinical records
• Patient level consolidated database
• Anonymised data
• Longitudinal data for 15+ years
• Validated against external and internal
measures
Study design & setting• Nested case control study• Study period Jan 1998-July 2008 • Cases were incident colorectal
cancer patients• 5 controls matched by
• Age• Sex• Practice• Calendar year
Exposure assessment :• Aspirin exposure analysis restricted to subjects with +10 and
+15yrs of prescribing data • any use:
• at least 1 script in 13-120 months and 13 to 180 months prior to the index date (date of diagnosis in the case)
• Years of exposure: • up to 1 years• 1 to 2 years• 3 to 5 years• 6 to 9 years• 10 to 14 years
Statistical analysis• Multiple imputations
• ICE procedure in STATA• 5 imputed datasets• Rubin’s rule’s to combine estimates
• Conditional logistic regression• Odds ratios + 95% CI ( unadjusted & adjusted)• 1% significance level
Study Sample:14,948 incident cases
of colorectal cancer
1998/2008
9534 cases
with 10 years of
medical records
6643 cases
with 15 years of
medical records
35,013 controls
with 10 years of
medical records
20,652 controls
with 15 years of
medical records
Confounding factors :
• Body mass index• in kg/m2
• Smoking status• Non-smoker• Ex-smoker• Smoker
• Socio-economic status (Townsend score for post code)• quintiles
• Morbidities• CVD • Diabetes• High BP• Osteoarthritis• Colitis• Crohn’s disease• Rheumatoid arthritis
Aspirin – median dose prescribed
10 year cohort 15 year cohortTablet dose (n = 10,073) (n = 6,506)
≥ 75 mg 77% 78%
76 – 150 mg 16% 15%
151 – 300 mg 5% 5%
>300 mg 2% 2%
Cases (%) Controls (%)
Unadjusted odds ratio
Adjusted odds ratio
P-value
(n=6643) (n=20652)(95% CI)
(95% CI)
Any use 1572 (23.7) 4934 (23.9) 1.03 (0.96 to 1.11) 0.98 (0.91 to 1.07) 0.709
No use 5071 (76.3) 15718 (76.1) 1.0 reference 1.0 reference
Up to 365days 464 (7.0) 1369 (6.6) 1.07 (0.96 to 1.20) 1.04 (0.92 to 1.17) 0.522
1 to 3 years 453 (6.8) 1304 (6.3) 1.10 (0.98 to 1.24) 1.05 (0.93 to 1.19) 0.418
4 to 6 years 373 (5.6) 1253 (6.1) 0.97 (0.86 to 1.10) 0.91 (0.79 to 1.04) 0.160
7 to 9 years 196 (3.0) 655 (3.2) 0.99 (0.84 to 1.17) 0.90 (0.75 to 1.09) 0.279
10 to 14 years 86 (1.3) 353 (1.7) 0.83 (0.65 to 1.06) 0.73 (0.56 to 0.94) 0.017
Cumulative exposure to aspirin in 1 to 15 yr period prior to CRC diagnosis / index date
10 to 14 years (164) 0.81 (0.66 to 0.98)
7 to 9 years (233) 0.87 (0.73 to 1.02)
4 to 6 years (378) 0.96 (0.84 to 1.10)
1 to 3 years (380) 0.97 (0.85 to 1.11)
Up to 1 year (417) 1.12 (0.99 to 1.26)
Exposure (N of cases) OR (95%CI)
.6 .8 1 1.2 1.4
Odds ratios and 95%CI are adjusted for deprivation, smoking, BMI, comorbidities, use of medicationReference group: No use of aspirin in 2 to 15 years prior the index date© QRESEARCH 2008 version 20
Adjusted odds ratios and 95% confidence intervals
Risk of colorectal cancer in patients using aspirinin 2 to 15 years prior to the index date
Risk of Colorectal cancer in patients using aspirin in 1-15 yr period prior to CRC diagnosis / index date
Cases (%) Controls (%)
Unadjusted odds ratio
Adjusted odds ratio
P-value
(n=9534) (n=35013) (95% CI) (95% CI)
Any use 2147 (22.5) 7926 (22.6) 1.03 (0.97 to 1.09) 0.98 (0.91 to 1.04) 0.472
Years of use
No use 7387 (77.5) 27087 (77.4) 1.0 reference 1.0 reference
Up to 365 days 614 (6.4) 2281 (6.5) 1.01 (0.92 to 1.11) 0.98 (0.88 to 1.08) 0.635
2 to 4 years 842 (8.8) 2944 (8.4) 1.08 (1.00 to 1.18) 1.03 (0.94 to 1.13) 0.524
5 to 6 years 329 (3.5) 1194 (3.4) 1.04 (0.91 to 1.18) 0.96 (0.83 to 1.10) 0.522
7 to 10 years 362 (3.8) 1507 (4.3) 0.93 (0.82 to 1.05) 0.85 (0.74 to 0.97) 0.017
Cumulative exposure to aspirin in 1 to 10 yr period prior to CRC diagnosis / index date
CRC cases Controls unadj OR adj OR
No use
7387 (77.5)
27087 (77.4) 1.0 reference 1.0 reference
P
value
Up to 1 year 547 (5.7) 1946 (5.6) 1.06 (0.96- 1.17) 1.02 (0.92- 1.13) 0.712
1 to 3 yrs 742 (7.8) 2621 (7.5) 1.07 (0.98- 1.17) 1.02 (0.93- 1.12) 0.703
4 to 6 yrs 359 (3.8) 1254 (3.6) 1.08 (0.95- 1.22) 1.00 (0.88 -1.14) 0.972
7 to 10 yrs 499 (5.2) 2105 (6.0) 0.91 (0.82- 1.01) 0.82 (0.73 -0.93) 0.001
Exposure to aspirin in 1 to 10 yr period prior to CRC diagnosis / index date
7 to 9 years (499) 0.82 (0.73 to 0.93)
5 to 6 years (359) 1.00 (0.88 to 1.14)
1 to 4 years (742) 1.02 (0.93 to 1.12)
Up to 1 year (547) 1.02 (0.92 to 1.13)
Exposure (N of cases) OR (95%CI)
.6 .8 1 1.2 1.4
Odds ratios and 95%CI are adjusted for deprivation, smoking, BMI, comorbidities, use of medicationReference group: No use of aspirin in 2 to 10 years prior the index date© QRESEARCH 2008 version 20
Adjusted odds ratios and 95% confidence intervals
Risk of colorectal cancer in patients using aspirinin 2 to 10 years prior to the index date
Risk of Colorectal cancer in patients using aspirin in 1-10 yr period prior to CRC diagnosis / index date
Conclusions• Patients taking low dose aspirin have a
reduced risk of Colorectal cancer
• An 18% reduction in risk is evident after more than 7yrs of aspirin use
• Effect not consistent with being COX-2 mediated
Methodological strengths• Large sample size and representative
population• Data electronically collected – unlikely
misclassification bias • Data collected before the diagnosis – no
recall bias• Excluded prescriptions 12 months prior to
cancer diagnosis
Baseline characteristics (15 years of data):Cases
n=9,534 Controls
n=35,013
Males (number, percent) 5,447 (57.1) 19,980 (57.1)
Age in years (median, IQR) 71 (63 to 78) 72 (64 to 78)
Months of records (median, IQR) 243 (173 to 417) 248 (176 to 1422)
Body mass index (median, IQR) 26.2 (23.7 to 29.2) 26.1 (23.7 to 29.0)
Smokers (number, percent) 1,325 (13.9) 4,941 (14.1)
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