A single-arm phase II trial of combined chemotherapy with S-1, oral leucovorin, and bevacizumab in heavily pre-treated patients with metastatic colorectal cancer

BACKGROUND: The mean 5–6-month survival after failed standard chemotherapy for metastatic colorectal cancer (mCRC) necessitates more effective treatments for refractory mCRC. For untreated mCRC, S-1 + oral leucovorin (SL) therapy offers promising results without severe toxicity. The ML18147 trial demonstrated that bevacizumab (Bev) prolongs overall survival after mCRC progression. We conducted a single-centre phase-II trial to evaluate the safety and efficacy of SL/Bev combination chemotherapy as mCRC salvage therapy. METHODS: Major eligibility criteria were confirmed adenocarcinoma diagnosis; age >20 years; Eastern Cooperative Oncology Group performance status, 0–2; and progression after administration/intolerance of/to approved drugs for mCRC. (5-FU, oxaliplatin, irinotecan, Bev, and anti-EGFR antibody, if KRAS wild-type). S-1 (80–120 mg/body) and leucovorin (25 mg) were orally administered in a 1-week-on/1-week-off schedule. Bev (5 mg/kg) was administered on day 1 of every 2-week cycle. The primary endpoint was disease control rate (DCR). RESULTS: A total of 31 patients were enrolled. DCR was 65 % [95 % confidence interval (CI), 48–100 %] and the response rate was 7 % (95 % CI, 0.7–22 %). One patient showing partial response to SL/Bev had a BRAF-mutant tumor. Median progression-free survival and overall survivals were 5.3 [95 % CI, 2.1–9.3] and 9.9 [95 % CI, 7.4–NA] months, respectively. The most-frequent grade-3/4 adverse events were mucositis (26 %) and diarrhea (11 %), which were manageable by dose reduction/interruption. CONCLUSIONS: SL/Bev showed impressive activity in refractory mCRC and was tolerable, suggesting its potential as an alternative chemotherapy for refractory mCRC. TRIAL REGISTRATION: This study has been registered in University Hospital Medical Information Network (UMIN) Clinical Trials Registry (IDUMIN000009083) on 11 October 2012. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12885-015-1606-1) contains supplementary material, which is available to authorized users.