For PFS, the hazard ratio of primary tumor location was 0.252 in favor of left-sided tumors (p = 0.013, 95 % CI 0.085–0.745), 0.780 in favor of wild-type (p = 0.411, 95 % CI 0.432–1.140) for KRAS mutation, and 0.487 (p = 0.056, 95 % CI 0.233–1.017) for interaction between primary tumor location and KRAS mutation. The gene discussed is KRAS; the disease is neoplasm.