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ABSTRACT #4036 (Sat. June 2, 2007: 2:00-6:00pm)

Association between exposure to bevacizumab (BV) beyond first progression (BBP) and overall survival (OS) in patients (pts) with metastatic colorectal cancer (mCRC): Results from a large observational study (BRiTE)

A. Grothey1, M. Sugrue2, D. Purdie2, P. Chiruvolu2, W. Dong2, E. Hedrick2, D. Sargent1, M. Kozloff3, on behalf of the BRiTE Study Investigators 1Mayo Clinic College of Medicine, Rochester, MN; 2Genentech, Inc., South San Francisco, CA, 3Ingalls Hospital and the University of Chicago, Harvey, IL

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• Bevacizumab (Avastin®, BV), a recombinant humanized monoclonal antibody against vascular endothelial growth factor (VEGF), increases overall survival (OS) and progression-free survival (PFS) when added to 1st-line or 2nd-line chemotherapy (CT) regimens in patients with metastatic colorectal cancer (mCRC).

• BRiTE (the 1st-Line Bevacizumab Regimens: Investigation of Treatment Effects and Safety) is a BV treatment registry, initiated early in 2004 to evaluate the safety and efficacy of BV in combination with CT in a large, less-selected community-based population of patients with previously untreated mCRC.

• No data exist on the effects of BV beyond 1st PD (BBP) or on the optimal duration of VEGF inhibition, including long-term safety and efficacy effects of using BV beyond 1st-line (i.e. BBP).

• A previous report from BRiTE showed a longer than expected median OS (27.1 months, 95% CI: 24.8-NE), with similar 1st-line PFS (median 10.1 months, 95% CI:9.7-10.4) compared with historical mCRC trials (Table 1), suggesting a significant impact of Post-PD survival on extending OS as observed in the BRiTE registry.

• Observational studies, such as BRiTE, in which data are collected prospectively for a long period of time on a large, less-selected patient population, provide important clinical outcomes data that may be generalized to typical patients in clinical practice. This is an interim report of an ongoing observational study reflecting data as of the January 21, 2007 data cutoff.

INTRODUCTION

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Table 1. Historical Survival Results With Various CT Regimens (With or Without BV) for 1st-Line Treatment of mCRC

*Control group included both 5-FU/LV and IFL.

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OBJECTIVE

• To explore the impact of BV exposure beyond 1st PD (BBP) on survival in patients who received BV as part of 1st-line treatment, in the context of various other pre- and post-treatment variables.

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METHODS (Study design and treatment)

• BRiTE, as an observational study, is distinct from a randomized controlled trial in terms of objectives, patient eligibility, treatment, patient assessments, and data collection (Table 2).

• Data were collected prospectively via electronic data capture at baseline and subsequently every 3 months. Dates related to BV and CT treatment were collected for the initiation of therapy, changes in therapy, and discontinuation of therapy. Dates of actual administration of BV or CT were not collected on the CRFs. Unless a change or discontinuation of therapy was indicated (either for BV or CT), it was assumed that the therapy continued as initially specified. Any gap in BV treatment of < 28 days was considered continuous BV treatment.

• Sites were only reimbursed for data; no compensation was provided for any laboratory tests or patient assessments.

• BV was not supplied by the sponsor (Genentech, Inc.).

• For the purpose of this analysis, BBP was defined as exposure to BV >28 days after 1st PD (patients who discontinued BV within 28 days after PD were considered as not exposed to BBP); there was variability observed in patterns of use of BBP, including continuous and discontinuous use.

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METHODS (Patient population)• Patients were required to meet the following 3 criteria to enroll in BRiTE:

– Metastatic or locally advanced and unresectable CRC who have not received prior therapy for their metastatic disease

– Receiving BV in combination with 1st-line CT– Signed informed consent

• There were no exclusion criteria.– Patients with poor performance status (e.g. ECOG PS ≥2) were not excluded from

BRiTE.

Limitations of the Analysis

• Patients were not randomized to receive BBP.

• Actual administration dates for BV and CT were not collected. Some minimal degree of mis-classification of BBP use is likely. However, a sensitivity analysis that randomly reclassified 10% of patients did not alter the conclusions.

• As patients who survived longer had a greater potential to be treated with BBP, the small group of patients that received BV late in their Post-PD therapy could contribute to inherent bias.

• Potential for unmeasured factors to confound the analysis.

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METHODS (Statistical analyses)• Patients who had progressed (i.e. 1st PD) were grouped based on their treatment post 1st

PD into 3 subgroups: 1) No treatment, 2) Post-PD Treatment (CT/EGFR inhibitor) without BV (No BBP), and 3) Post-PD (CT/EGFR inhibitor) Treatment with BV (BBP). Patients who received BV alone post 1st-PD (n=19) were excluded from the analyses. The BBP subgroup did not require that both BV and CT/EGFR inhibitors be administered concurrently.

• Overall survival (OS) was measured from the date of initiation of 1st-line treatment to death. The remaining patients were censored at study termination (due to loss to follow-up, patient’s decision, investigator’s decision, or sponsor’s decision) or the data cutoff date (January 21, 2007).

• Survival beyond 1st PD was measured only for patients who had disease progression, and was from the date of 1st PD to death (Figure 1). This was the primary endpoint used in the BBP analysis.

• Time to 1st PD (TTP) was measured from the date of initiation of 1st-line treatment to the occurrence of investigator-assessed 1st PD (Figure 1).

• OS and survival beyond 1st PD were summarized using the Kaplan-Meier method (including medians, 95% confidence intervals, 1-year survival rates and survival curves).

• Cox’s proportional hazard model was used to assess the independent effects of pre- and post-treatment patient-related factors on survival beyond 1st PD, including age at 1st PD, baseline (start of 1st-line treatment) ECOG PS, albumin, alkaline phosphatase, and site of primary tumor, 1st-line CT regimen, 1st-line TTP, best 1st-line response, exposure to all 3 active CT agents (5-FU [or capecitabine], irinotecan, and oxaliplatin), exposure to EGFR inhibitors, (the majority [90%] being cetuximab), and BBP.

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Table 2. Comparison Between BRiTE as a Treatment Registry and a Typical Randomized Controlled Trial (RCT)

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RESULTS

• A total of 1953 evaluable patients (defined as those who received BV and CT as 1st-line treatment of mCRC) were enrolled from 248 study sites in 49 states between February 2004 and June 2005.

• The median follow-up time of this interim report from BRiTE was 19.6 months by the January 21, 2007 data cutoff date.

• A total of 1445 (74%) patients had an investigator-assessed 1st PD; among these, 642 (44%) patients received Post-PD Treatment with BV (BBP), 531 (37%) patients received Post-PD Treatment , but no BV (No BBP); and 253 (18%) patients received No Treatments Post-PD (Figure 2).

• As of January 21, 2007, 850 patients (44%) were still alive and in active follow-up; 171 patients (8.8%) were lost to follow-up or dropped out of the study.

Enrollment, baseline characteristics, and follow-up

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Figure 1. Schematic of Disease Progression and Interim Disposition of Patients in BRiTE

Figure 1. Schematic of Disease Progression; OS=overall survival; TTP=time-to-progression

Figure 2. Interim Disposition of Patients in BRiTE (N=1953 with 1445 1st PD and 932 Deaths Reported as of the January 21, 2007 Data Cutoff)*Nineteen patients received post-progression treatment with BV only and have been excluded from the BBP analysis. The remaining 508 patients have not yet had PD noted by investigator assessment.

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Figure 3. A) Graphical Representation of BV Use in BBP Patients and B) Frequency Distribution of Time from 1st PD to Start of BV Post 1st PD for Patients in the BBP Subgroup

• The pattern of BV use for patients who used BBP is shown in Figure 3. – 312 of 642 (49%), received BV continuously from 1st-line to beyond 1st PD (Figure 3A).– The majority of patients in the BBP subgroup (n=571, 89%) either used BV continuously into

2nd-line, or restarted BV within the 1st 4 months post-1st PD (Figure 3B).– 132 of the 642 BBP patients (20%) discontinued BV prior to 1st PD and restarted BV within 28

days of 1st PD.– 198 of the 642 BBP patients (31%) discontinued BV either prior to or at 1st PD and restarted

BV >28 days after 1st PD.

Figure 3A. Graphical Representation of BV Use in BBP Patients Orange lines represent the time course of treatment with BV in days for each patient who has progressed (n=642) with overlay of time of 1st PD (blue asterisks]

Figure 3B. Frequency Distribution of Time from 1st PD to Start of BV Post 1st PD for Patients in the BBP Subgroup

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RESULTS (continued)

• The proportion of patients with ECOG PS 0 was higher in the BBP than in the No BBP subgroup (50.2% versus 39.9%) (Table 3).

• The BBP and No BBP subgroups were balanced on:

– Use of 1st-line CT– Proportion of patients exposed to all 3 active CT agents– TTP – 1st-line exposure to BV

• Total duration of BV use was longer in the BBP subgroup, as expected.

• Of the 1445 patients with PD, 542 (37.5%) used an EGFR inhibitor post 1st PD (including BBP and No BBP); 489 of these (90%) used cetuximab.

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Table 3. Baseline and Post-Baseline Characteristics of Overall Population and Patient Subgroups Based on Treatment Beyond 1st PDa

aNineteen patients received post-1st PD treatment with BV only and have been excluded from the BBP analysis. bActive CT agents included 5-FU [or capecitabine], irinotecan, and oxaliplatin over entire course of treatment.

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Table 4. Survival Outcomes of Total Population and Patient Subgroups Based on Treatment Post 1st PD

• A longer median OS in the BBP subgroup was observed compared with the No BBP subgroup (Table 4).

• A longer survival beyond 1st PD was observed in the BBP subgroup versus the No BBP subgroup.

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• Figure 4 displays the Kaplan-Meier curve for survival beyond 1st PD by subgroups based on treatment beyond 1st PD (1st PD occurred at 0 months).

• Figure 5 displays the Kaplan-Meier curve for OS by subgroups based on treatment beyond 1st PD.

Figure 4. Kaplan-Meier Estimates of Survival Beyond 1st PD by Subgroups Based on Post-PD Therapy

Figure 5. Kaplan-Meier Estimates of OS by Subgroups Based on Post-Progression Therapy

Figures 4, 5. Kaplan-Meier Estimates of A) Survival Beyond 1st PD and B) OS

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Table 5. Incidence of BV-targeted Safety Events in BRiTE Patient Subgroups Based on Treatment Beyond 1st PD: Overall, pre- and Post-PD

• The proportion of patients with BV-targeted safety events did not differ appreciably between the BBP subgroup compared with the No BBP subgroup (Table 5).

• The incidence of BV-targeted events (ATE, grade 3/4 bleeding events, and GI perforation) post-1st PD did not appear to increase appreciably in the BBP subgroup.

• While the duration of exposure to BV, as well as survival, were significantly longer in the BBP subgroup, there was no apparent increase in the incidence of BV-specific AEs.

HTN=hypertension; ATE=arterial thromboembolic event (includes myocardial infarction [MI], cerebral vascular accident [CVA], transient ischemic attack [TIA], and sudden cardiac death); aPre- and post-1st PD dates were not collected; bPercentages of pre and post safety events do not necessarily sum to the Total due to missing onset date, and because a patient may be counted in both “Pre 1st PD” and “Post 1st PD” if they had more than one safety event, but patients are counted only once in the total percentage.

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Table 6. Multivariate Analysis of Pre- and Post-Treatment Variables on Survival Beyond 1st PDa

• In a multivariate analysis that included pre- and post-treatment variables, BBP was independently associated with increased survival beyond 1st PD (p<0.001).

• Despite a higher proportion of patients with ECOG PS 0 in the BBP subgroup

(Table 3), this did not confound the analysis, since adjusting for ECOG PS did not appreciably change the HR associated with BBP.

• Findings were similar when OS was used as the outcome in the multivariate analysis instead of survival beyond 1st PD.

a1st-line CT regimen was also included in the model. 3 CT agents include 5-FU (or capecitabine), irinotecan, and oxaliplatin.

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Sensitivity Analysis• When compared with No BBP patients, patients who received BV continuously from

1st-line into Post-PD had a similarly improved survival (adjusted HR=0.51; 95% CI: 0.42, 0.62).

• To remove any bias introduced by delays in starting BV Post-PD, a multivariate analysis was performed whereby all patients that received BV more than 3 months Post-PD were classified as No BBP and were censored at the time of starting BBP. The resulting HR associated with BBP compared with No BBP was 0.54 (95% CI: 0.45, 0.64).

• A site’s treatment practice could influence patterns of BBP use as well as the associated survival outcomes. These practices are unmeasureable and cannot be included in the multivariate analysis. An additional analysis was therefore performed to assess the impact on survival outcomes of being treated at a “High” BBP use site versus a “Low” BBP use site. We then assessed whether the survival impact of treatment at “High” BBP sites was due primarily to patients’ actual use of BBP at those sites. The following section outlines the results of the impact of site propensity for BBP use on the survival outcomes (Table 7).

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Table 7. Survival Outcomes of Subgroups Based on the Propensity of Sites to Use BV and CT Beyond 1st PD

• Patients treated at sites with a high propensity to use BBP (highest quartile) had a longer OS and survival beyond 1st PD than patients treated at sites with a low propensity to use BBP (lowest quartile) (Table 7).

– A multivariate analysis was performed including all variables shown in Table 6, and site propensity to use BBP (Low, Medium, High): The adjusted HR associated with high BBP use sites versus low BBP use sites was 0.63 (95% CI: 0.48, 0.83; p=0.001).

• To examine whether patients treated at sites with a high propensity to use BBP had improved survival independent of actual use of BBP, a multivariate analysis was performed including both of these variables in the same model (i.e. site propensity to use BBP and actual use of BBP).

– After adjusting for actual use of BBP, site propensity to use BBP was no longer significantly associated with survival (p=0.15).

– The adjusted HR associated with actual patient use of BBP was 0.46 (95% CI: 0.38, 0.55).– This suggests that the association between site propensity to use BBP and survival appears

to be fully explained by the patients’ actual use of BBP.

aMedians and their 95% CIs are from KM estimates. NE indicates that the statistic is not estimable.bSites were categorized based on their propensity to use BBP. This “Site Propensity” was calculated as the percentage of patients at a site that were treated with BBP divided by the total number of patients who had 1st PD at the site. This Site Propensity was then used to subgroup sites into quartiles: the lowest quartile (Low BBP, 0% to ≤22,2%), the middle two quartiles (medium BBP, >22.2% to ≤66.7%), and the highest quartile (high BBP, >66.7%). Quartiles were determined by the number of sites.

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SUMMARY

• The median OS in BRiTE exceeds 2 years (25.1 months) and is longer than the OS previously reported from the pivotal phase III trial AVF2107 (IFL+BV, median OS 20.3 months), despite an unselected population.

• Patients treated with BBP had a substantially longer median OS and median survival beyond 1st PD compared with patients that did not receive BV (No BBP) after their 1st PD.

• In a multivariate analysis, BBP was significantly associated with improved survival outcomes (i.e. OS and survival beyond 1st PD).

• The overall rates of BV-targeted safety events prior to 1st PD or after 1st PD were similar in patients who received BBP compared with those patients who received BV only during 1st-line therapy.

• Patients treated at sites that showed a high propensity for using BBP appeared to show a longer median survival beyond 1st PD compared with patients treated at sites that had a low propensity for using BBP.

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CONCLUSIONS• These results from the BRiTE observational study are the first report of an improvement in

survival outcomes associated with BBP for patients who started BV in the 1st-line setting.

• These findings support the evaluation of BBP in the prospective, randomized phase III Intergroup trial S0600/iBET: mCRC pre-treated with FOLFOX+BV or CAPOX+BV, at 1st PD followed by:

– (FOLF)IRI/Cetuximab or– (FOLF)IRI/Cetuximab + BV (5mg/kg q2w) or– (FOLF)IRI/Cetuximab + BV (10mg/kg q2w)

• Observational cohort studies like BRiTE, in which data are collected prospectively for a long period of time on a large, less-selected patient population:

– Provide important clinical outcomes data that may be generalized to typical patients in clinical practice

– Generate specific hypotheses that may be tested in future randomized controlled trials

• Provide the basis for further investigation of clinical outcomes associated with BV use in new observational studies, e.g. the ongoing ARIES (AVF3991) BV treatment registry, which includes 1st- and 2nd-line mCRC patients and 1st-line NSCLC patients who are receiving BV as part of their treatment

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