Phase II study of S-1-based sequential combination chemotherapy including oxaliplatin plus bevacizumab and irinotecan with or without cetuximab for metastatic colorectal cancer: the SOBIC trial

Background Fluorouracil and leucovorin combined with oxaliplatin or irinotecan plus bevacizumab (Bmab) or cetuximab (Cmab) are now widely accepted treatment options as first-line or second-line chemotherapy for metastatic colorectal cancer (mCRC). Sequential chemotherapy with oral 5-FU backbone for mCRC without using central venous ports is beneficial for both patients and physicians. We designed the SOBIC trial to validate the effectiveness of the first- and second-line oral combination chemotherapy for mCRC. Patients and methods From May 2010 through March 2013, 52 patients were enrolled from 47 institutions in the Hyogo Colorectal Cancer Surgery Group. First-line chemotherapy was S-1 + oxaliplatin (SOX) plus Bmab, and second-line chemotherapy after first-line failure was irinotecan + S-1 (IRIS) + Cmab, IRIS + Bmab, or IRIS based on theKRAS status. Results The 50 finally included patients received first-line chemotherapy. Second-line therapy was administered to 20 patients (40%): 12 patients received IRIS + Cmab and 8 patients received IRIS + Bmab. The median follow-up period was 48.6 months (range 35-67 months). The median second progression-free survival was 24.2 months (95% confidence interval [CI] 17.7-35.2). The response rate after first- and second-line chemotherapy was 46.7% and 15%, respectively. The median overall survival was 35.2 months (95% CI: 27.8 to not reached). The main grade 3-4 adverse events were sensory neuropathy (18%) and fatigue (10%). There were no treatment-related deaths. Conclusion Sequential S-1-based combination regimens including oxaliplatin, irinotecan, Bmab, and Cmab were beneficial for patients with mCRC.