Benefit of oxaliplatin in stage III colon cancer according to IDEA risk groups: Analysis of MOSAIC and C-07 trials.

Abstract

118 Background: The IDEA pooled analysis compared 3 to 6 months of adjuvant chemotherapy for stage III colon cancer. The overarching goal was to reduce chemotherapy-related toxicity, mainly oxaliplatin-induced neuropathy. Patients were classified into low-risk and high-risk, suggesting low-risk patients may be offered only 3 months of treatment. In our previously published analysis using retrospective data from the National Cancer Database (NCDB) we showed similar benefit for oxaliplatin in both low and high IDEA risk groups. In the current study, we aimed to test our hypothesis using data from the two large clinical trials assessing the benefit of oxaliplatin in the adjuvant setting, namely, MOSAIC and C-07. Methods: Using the MOSAIC and C-07 previously published studies, we identified 1,754 low-risk and 1,302 high-risk individuals with stage III colon cancer, according to the IDEA classification. We used multivariate COX regression to evaluate the magnitude of survival differences between IDEA risk groups, according to oxaliplatin use. The analysis was adjusted for age, primary tumor sidedness, tumor stage, tumor grade and lymph node ratio. Results: Individuals with IDEA low-risk derived overall survival (OS), disease-free survival (DFS) and recurrence-free survival (RFS) benefit from the addition of oxaliplatin to adjuvant chemotherapy, with adjusted hazard ratios (HRs) of 0.78 (0.65-0.94), 0.75 (0.63-0.89) and 0.74 (0.62-0.90). Similarly, individuals with IDEA high-risk derived OS, DFS and RFS benefit from the addition of oxaliplatin to adjuvant chemotherapy, with adjusted HRs of 0.84 (0.71-0.99), 0.81 (0.69-0.95) and 0.82 (0.69-0.97). Conclusions: IDEA risk classification per se does not predict benefit from addition of oxaliplatin to adjuvant chemotherapy in stage III colon cancer, according to analysis of the MOSAIC and C-07 studies. Funding: NCI U10CA-180868, NCI U10CA-180822.