S-1 and oxaliplatin (SOX) plus bevacizumab versus mFOLFOX6 plus bevacizumab as first-line treatment for patients with metastatic colorectal cancer: updated overall survival analyses of the open-label, non-inferiority, randomised phase III: SOFT study

OBJECTIVE The SOFT study previously demonstrated that S-1 and oxaliplatin (SOX) plus bevacizumab was non-inferior to l-leucovorin, fluorouracil and oxaliplatin (mFOLFOX6) plus bevacizumab in terms of the primary end point of progression-free survival (PFS) as first-line chemotherapy for metastatic colorectal cancer (mCRC). The overall survival (OS) data were immature at the time of the primary analysis. METHODS A total of 512 patients were enrolled and randomly assigned to receive either mFOLFOX6 plus bevacizumab (5 mg/kg of bevacizumab, followed by 200 mg/m2 of l-leucovorin given simultaneously with 85 mg/m2 of oxaliplatin, followed by a 400 mg/m2 bolus of 5-FU on day 1 and then 2400 mg/m2 of 5-FU as an intravenous infusion over the course of 46 hours, every 2 weeks) or SOX plus bevacizumab (7.5 mg/kg of bevacizumab, 130 mg/m2 of oxaliplatin on day 1 and 40-60 mg of S-1 two times per day for 2 weeks, followed by a 1-week rest). The primary end point was PFS. After the primary analysis, the follow-up survey was cut-off on 30 September 2013, and the final OS data were analysed. RESULTS With a median follow-up of 37.7 months, the median survival time (MST) was 29.7 months with mFOLFOX6 plus bevacizumab and 29.6 months with SOX plus bevacizumab (HR, 1.018; 95% CI 0.823 to 1.258). Median PFS was 11.7 months in the mFOLFOX6 plus bevacizumab group and 12.2 months in the SOX plus bevacizumab group (HR, 1.051; 95% CI 0.876 to 1.262; pnon-inferiority=0.0115). CONCLUSION Our results reconfirmed that SOX plus bevacizumab is non-inferior to mFOLFOX6 plus bevacizumab in terms of PFS. MST did not differ between the groups. SOX plus bevacizumab is considered an effective regimen for first-line chemotherapy in patients with mCRC and can be used instead of mFOLFOX6 plus bevacizumab. TRIAL REGISTRATION NUMBER JapicCTI-090699.