FOLFOXIRI versus doublet-regimens in the first-line therapy of MSI-S right-sided (RS) metastatic colorectal cancer (mCRC): A survival analysis.

Abstract

e15060 Background: Microsatellite stable (MSI-S) RS mCRC patients (pts) have a worse prognosis relative to left sided tumors for overall survival (OS). The present analysis aims to test the hypothesis that a triplet-regimen is superior compared to doublet-regimens (DR; FOLFOX or FOLFIRI) for OS. Methods: Pts with treatment-naive RS mCRC at MD Anderson Cancer Center between January/2011 to December/2018 were selected. We compared the progression-free survival (PFS) and OS of mCRC pts treated with FOLFOXIRI versus DR. Pts treated with anti-EGFR therapy were excluded. Results: A total of 37 pts were treated with FOLFOXIRI and 111 pts with DR. There were no statistical difference between groups regarding gender, KRAS and BRAF mutations, peritoneal metastasis and bevacizumab use. There were statistical difference in age (median: 46y vs 59y) and metastasectomy rates (14% vs 32%) (p < 0.001). KRAS mutation was found in 65% of the population. Median follow-up was 55.3m. Median PFS was 6.5m vs 11.2m (HR: 1.30 95% CI 0.85 – 1.99) and median OS was 17.0m vs 26.3m (HR: 1.01 95% CI 0.60 – 1.68). By univariate analysis, pts who have undergone metastasectomy had superior PFS (14.9m vs 9.2m; p<0.001) and OS (32.4m vs 22.9m; p=0.003). By multivariate analysis adjusted for age, BRAF mutation, metastasectomy, bevacizumab use and, treatment regimen, only age and metastasectomy had prognostic influence for PFS (p=0.039 and p=0.026, respectively). Conclusions: Despite RS having a poor prognosis for OS, our study does not suggest that RS mCRC pts benefit from intensive treatment. Randomized clinical trials may suggest more individualized therapies.