The efficacy of first-line IRIS with or without bevacizumab in patients with metastatic colorectal cancer: Including multivariate analysis of two phase II studies.

Abstract

603 Background: The safety and efficacy of first-line IRIS (S-1 in combination with irinotecan) and IRIS/Bev (IRIS in combination with bevacizumab [Bev]) have been evaluated in patients with metastatic colorectal cancer (mCRC). To date, no randomized studies comparing these regimens have been performed. This retrospective analysis compared efficacy data for the two regimens from separate phase II studies performed at Hokkaido Gastrointestinal Cancer Study Group (HGCSG). Methods: Patients with histologically confirmed unresectable metastatic or recurrent CRC and received no prior chemotherapy were enrolled. In the first trial, patients received irinotecan 100 mg/m2 on day 1,15 and oral S-1 40 mg/m2 twice daily on days 1-14 every 4 weeks (IRIS study: HGCSG0302). In the second trial, patients received the same regimen plus Bev 5 mg/kg on day 1,15 (IRIS/Bev study). Results: A total of 40 and 52 patients were enrolled the IRIS and IRIS/Bev studies, respectively. Patient characteristics were generally similar in both groups, whereas there were more cases of good performance status and less number of metastatic organ in IRIS/Bev group. The median overall survival was 39.6 months in IRIS/Bev, as compared with 23.4 months in IRIS, corresponding to a hazard ratio for death of 0.418 (p<0.001). The median progression-free survival was 17.0 months in IRIS/Bev, as compared with 8.6 months in IRIS (hazard ratio for disease progression, 0.402; p < 0.001); the corresponding response rate were 63.5 percent and 52.5 percent (p = 0.393). In a multivariate analysis of PFS and OS, IRIS/Bev was significantly associated with longer PFS and OS compared with IRIS alone. Conclusions: In this retrospective comparison of two studies, the addition of Bev to IRIS appeared to improve outcome compared with IRIS alone in the first-line treatment of patients with mCRC.