Abstract
Background: Although chemotherapy for metastatic colorectal cancer (mCRC) has improved, the standard chemotherapy regimens for patients with RAS wild-type mCRC remain debated.Methods: This randomized phase II, open-label, multicenter study compared the efficacy and safety of S-1 and oxaliplatin (SOX)+bevacizumab (B-mab) with SOX+cetuximab (C-mab) in patients with previously untreated recurrent advanced CRC with wild-type KRAS. Between February 2012 and October 2016, 45 patients were enrolled.Results: Overall response rates were 59.1% and 43.5% (p=0.29) and disease control rates were 90.9% and 91.3% (p=0.96) in the SOX+B-mab and SOX+C-mab groups, respectively. Median overall survival (OS) was 25.3 and 15.5 months (HR=0.607, p=0.167) and median progression-free survival (PFS) were 11.7 and 5.5 months (HR=0.558, p=0.077) in the SOX+B-mab and SOX+C-mab groups, respectively. The OS and PFS of patients with early tumor shrinkage (ETS) were not significantly different in the SOX+B-mab group. However, they were significantly better when ETS was ≥20 in the SOX+C-mab group (p=0.032 and p=0.003, respectively).Conclusions: The efficacy and safety of SOX+B-mab and SOX+C-mab for wild-type KRAS recurrent advanced CRC as first-line chemotherapy were almost the same. Consideration of the treatment strategy based on ETS may improve patient prognosis, especially in patients receiving the SOX+C-mab regimen.Trial registration: UMIN Clinical Trials Registry (UMIN000006706)Date of registration: NOV/11/2011URL of trial registry record:https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000007920