WJOG6510G study compared cetuximab (Cmab) versus panitumumab (Pmab) in combination with irinotecan (IRI) for patients (pts) with KRAS exon2 wild-type (WT) metastatic colorectal cancer (mCRC) previously treated with fluoropyrimidine-, oxaliplation- and IRI- based chemotherapies. The study demonstrated that Pmab + IRI was not only non-inferior but slightly superior to Cmab + IRI in terms of PFS and OS (median PFS 4.3 months versus 5.4 months, HR 0.68, 95%CI 0.47-0.99, p = 0.040; median OS 11.5 months versus 14.9 months, HR 0.68, 95% CI 0.46-1.02, p = 0.06) (Sugimoto N, et al. ASCO-GI 2017). Here, we report predefined subgroup analyses of the study according to patient characteristics.
Pre-planned subgroup analyses investigated the homogeneity of treatment effects for PFS and OS across the following subgroups defined by age, gender, ECOG PS, histological type, prior resection of primary site, prior bevacizumab use, reason for oxaliplatin discontinuation, and primary tumor location. Cecum to transverse colon classified as right-sided CRC (RCRC), splenic flexure to rectum classified as left-sided CRC (LCRC).
Totally, 120 (Cmab arm 59, Pmab arm 61) pts were eligible for the analyses. The subgroup analyses in PFS and OS revealed favorable tendency of Pmab arm for almost all factors. Among patients with LCRC (n = 104), Pmab+IRI significantly improved PFS and OS relative to Cmab+IRI (median PFS 4.2 months versus 5.6 months, HR 0.65, 95% CI 0.44-0.97, p = 0.030; median OS 11.1 months versus 15.4 months, HR 0.62, 95% CI 0.40-0.96, p = 0.030). In contrast, in RCRC tumors, comparable survival outcomes were observed between Cmab arm and Pmab arm.
Pmab + IRI for pretreated mCRC patients was associated with favorable PFS and OS compared to Cmab + IRI, especially with left-sided colorectal tumors.
Clinical trial identification
Legal entity responsible for the study
West Japan Oncology Group (WJOG)
A. Tsuji: Honoraria: Daiichi Sankyo, Taiho Pharmaceutical, Chugai Pharma, Merck Serono, Takeda Pharmaceutical, Bristol-Myers Squibb Japan. Speakers\' Bureau: Chugai Pharma, Taiho Pharmaceutical, Takeda, Merck Serono. T. Moriwaki: Corporate-sponsored research: Taiho, Chugai, Takeda, Boelinger Ingelheim, Sanofi-Aventis, and Yakult Honsha. H. Satake: Honoraria from Bayer, Chugai Pharma, Eli Lilly Japan, Merck Serono, Takeda, Taiho Pharmaceutical, and Yakult Honsha. E. Baba: Speakers\' Bureau: Chugai Pharm, Eli Lilly. H. Taniguchi: Honoraria for speaking from Takeda and Merck Serono. Research funding from Takeda. I. Hyodo: Honoraria from Taiichi-Sankyo, Chugai, and Taiho Pharmaceutical Companies. All other authors have declared no conflicts of interest.