Impact Of Early Tumor Shrinkage On Long-Term Outcome In Metastatic Colorectal Cancer (Mcrc) Treated With 5fu Plus Irinotecan Plus Leucovorin (Folfiri) Or Capecitabine Plus Irinotecan Xeliri Plus Bevacizumab.

e14041 Background: The measurement of ETS at 8 weeks was reported to predict long-term outcome in first line mCRC treated with irinotecan based chemotherapy (CT) + cetuximab. This study has for aim to evaluate the impact of ETS on long-term outcome in patients (pts) receiving irinotecan based CT + bev. Methods: The pts treated in the randomized phase II trial ACCORD 13 (FOLFIRI + bev vs. XELIRI + bev) previously reported (Ducreux, ASCO 2009, abs 4086) were included in this post-hoc analysis with a 36 months follow-up. Based on the 8-weekly radiological assessments reported by the investigators, relative changes of the tumor size from baseline were dichotomized using a 20% decrease cut-off value. Univariable analyses for progression-free survival (PFS), and overall survival (OS) were based on logrank test. Multivariable analysis used Cox model and included ETS, Köhne prognostic score; age, sex, and treatment arm. Results: 2 pts out of 145 were excluded from this analysis because of early death. One patient had GI perforation at week 6 and was considered as non responder. ETS was observed in 87 pts out of 143 (61%). All the RECIST responders (46) had early shrinkage. Median PFS was 10 months and 9 months in pts with and without ETS. PFS rates were 97% and 75% at 6 months, 23% and 20 % at 12 months in the pts with and without ETS, (HR = 0.84; [0.59 – 1.20], p=0.35). Median OS were 33 months and 22 months for pts with or without ETS. OS rates were 93% and 79 % at 12 months in the pts with or without ETS, the corresponding rates at 24 months were 52% and 36 % (HR = 0.59; [0.36-0.97], p=0.04). The multivariable analysis showed that ETS had the strongest independent prognostic value when added to the OS model (HR = 0.54 [0.32-0.92] p=0.02), age: p=0.07, other variables: p>0.28. Conclusions: Combination of fluoropyrimidines + bev gives rapid responses. ETS is able to determine patients with prolonged survival rarely observed in mCRC. Despite the absence of effect of ETS on PFS, these results are similar or even better to those observed with CT + cetuximab. Their relevance in terms of daily clinical practice remains debatable and need to be confirmed.