Impact of adjuvant chemotherapy with 5-FU or FOLFOX in colon cancers with microsatellite instability: An AGEO multicenter study.

3508 Background: Microsatellite instability (MSI) is found in 12% of colon cancers (CC) and associated with a low recurrence rate after curative surgery. Adjuvant chemotherapy with 5-FU seems ineffective, but small studies recently suggest that adjuvant chemotherapy with FOLFOX could be effective (Zaanan et al.). The aim of this study was to analyze efficacy of adjuvant chemotherapy with 5-FU or FOLFOX in relapse-free survival (RFS) of MSI CC. Methods: This multicenter retrospective study included patients with stage II or III MSI CC with curative surgery between 2000 and 2012. High-risk stage II CC were defined by one of these criteria: stage T4, bowel obstruction, tumoral perforation, vascular emboli, lymphatic invasion, perinervous invasion, or a number of lymph nodes examined inferior to 10. Prognostic factors of RFS were analyzed in univariate and multivariate analysis using Cox model. Results: A total of 433 MSI CC patients were analyzed, including 57% and 43% stage II and III, respectively. Median ...