Predictive value of KRAS mutation status in metastatic colorectal cancer (mCRC) patients treated with capecitabine and bevacizumab (CAP B) maintenance …

3525 Background: The impact of KRAS mutation status in mCRC treated with anti-VEGF therapy is controversial. The randomized phase 3 CAIRO3 study showed benefit of first-line CAP-B maintenance treatment compared to observation in mCRC patients (pts) with stable disease or better after 6 cycles CAPOX-B. We investigated the predictive value of KRAS mutation status within the CAIRO3 study. Methods: We extracted tumor DNA from paraffin blocks and used Next Generation Sequencing (NGS) to detect mutations in KRAS exon 2-4. We supplemented this with KRAS data collected from local laboratories. We used stratified Cox regression models adjusted for baseline covariables to estimate hazard ratios (HR) and to analyze whether treatment effect was modified by KRAS mutation status. Time to first progression (PFS1), time to second progression after CAPOX-B reintroduction (PFS2, primary endpoint), time …