A new look at the IDEA classification: Defining novel predictive and prognostic markers in stage III colon cancer.

Abstract

845 Background: The IDEA pooled analysis compared 3 to 6 months of adjuvant chemotherapy for newly defined low- and high-risk stage III colon cancer patients, suggesting low-risk patients may be offered only 3 months of treatment. We aimed to evaluate the benefit of monotherapy vs doublet chemotherapy in low and high IDEA risk groups. Methods: Using the NCDB (2004-2014) we identified 56,728 and 47,557 individuals as low and high IDEA risk groups, respectively. We used multivariate COX regression to evaluate the magnitude of survival differences between IDEA risk groups, according to treatment intensity (doublet vs monotherapy). In a secondary analysis, we examined the predictive value of subgroups of age. Results: Low and high IDEA risk groups derived similar benefit from doublet chemotherapy compared to monotherapy, with hazard ratios of 0.83 (95%CI 0.79-0.86) and 0.80 (95%CI 0.78-0.83), respectively. The only subpopulations that did not benefit from doublet chemotherapy were low-risk patients above the age of 72 (HR = 0.95, 95%CI 0.90-1.01) and high-risk patients above the age of 85 (HR = 0.90, 95%CI 0.77-1.05). Conclusions: IDEA risk classification does not predict benefit from doublet chemotherapy in stage III colon cancer. However, omission of oxaliplatin can be considered in IDEA low-risk patients above the age of 72.