A Phase Ii Study Of Second-Line S-1/Cpt-11+Bev For Advanced Colon Cancer (Nccsg04): Subset Analysis By K-Ras, Egfr, Ugt1a1, And Previous Bevacizumab.

564 Background: We planned a phase II trial to evaluate the efficacy and safety of irinotecan, S-1, and bevacizumab (IRIS/Bev) as second-line therapy for patients with metastatic colorectal cancer (mCRC). The result of this study was reported an active and generally well-tolerated 2nd-line treatment for mCRC (Takii et al. ASCO-GI 2013 #496). We analyzed subset of EGFR, K-ras, UGT1A1, and previous Bev. Methods: The study design was multicenter, single-arm, open-label phase II study. Eligible patients had to have mCRC with confirmed diagnosis of adenocarcinoma, history of oxaliplatin containing regimen as first-line therapy, an age from 20 to 80 years, ECOG performance status (PS) of 0-1. S-1 65 mg/m2 daily p.o. was given on days 1-14 and Irinotecan 75mg/m2and bevacizumab 10mg/kg i.v. were given on days 1 and 15 of a 28-day cycle. We retrospectively examined progression-free survival (PFS), overall response rate (OR), overall survival (OS), time to treatment failure (TTF) and safety by K-ras, EGFR, UGT1A1, and previous Bev status. Results: Thirty-four patients were investigated. The OR was 21.1% (7/33) and disease control rate was 84.8% (28/33). Median PFS was 8.9 months, median TTF was 8.2 months and median OS was 23.4 months. Median PFS was 9.9 months on K-ras wild group and 6.6 months on K-ras mutant group (p = 0.517). Median OS was not reached on K-ras wild group and 16.4 months on K-ras mutant group (p = 0.097). The EGFR-negative case was three cases, and it did not become a data to compare because of small number. Median PFS was 8.5 months on previous Bev group and 9.9 months on previous no-Bev group (p = 0.637). Median OS was not reached on previous Bev group and 23.1 months on previous no-Bev group (p = 0.701). Median PFS, TTF and OS was no different between UGT1A1 wild group and mutant group. On safety analysis, there were no different between the two groups, respectively. Conclusions: IRIS/Bev is an active and well-tolerated second-line treatment for patients with mCRC. Only K-ras status influendced OS. Clinical trial information: UMIN000001631.