Comparison of first-line cetuximab and panitumumab plus doublet chemotherapies for left-sided colorectal cancer: a multicenter real-world observational study by the Japanese Society for Cancer of the Colon and Rectum.

<h4>Background</h4>For patients with left-sided metastatic colorectal cancer (mCRC), the recommended first-line treatment is anti-epidermal growth factor receptor (anti-EGFR) antibodies, such as cetuximab or panitumumab, plus doublet chemotherapy. However, the differences in outcomes between cetuximab and panitumumab remain unknown.<h4>Methods</h4>Clinical data of patients with left-sided all RAS or KRAS wild-type mCRC who received cetuximab or panitumumab plus doublet chemotherapy were retrospectively collected from 24 institutions in Japan. The patients were divided into two groups: the cetuximab and panitumumab groups. Overall survival (OS), progression-free survival (PFS), and response rate (RR) were compared between the two groups.<h4>Results</h4>A total of 233 patients were enrolled: 87 (37.3%) in the cetuximab group and 146 (62.7%) in the panitumumab group. Median OS, PFS, and RR of the cetuximab and panitumumab groups were 26.6 months (95% confidence interval [CI], 19.7-33.4) versus 31.8 months (95% CI, 25.7-37.9), 9.7 months (95% CI, 6.9-12.5) versus 12.4 months (11.1-13.7), and 57.8% versus 71.0%, respectively. In multivariate analysis, OS and RR were significantly better in the panitumumab group than in the cetuximab group (adjusted hazard ratio 0.69, 95% CI 0.50-0.99, p = 0.04; adjusted odds ratio 2.00, 95% CI 1.07-3.73, p = 0.03) and PFS was similar between the two groups (adjusted hazard ratio 0.75, 95% CI 0.55-1.01, p = 0.05).<h4>Conclusion</h4>As a first-line treatment for patients with left-sided all RAS or KRAS wild-type mCRC, panitumumab plus doublet chemotherapy may be suggested better efficacy outcomes than cetuximab plus doublet chemotherapy.