Impact of adyuvant chemotherapy treatment according to tumor primary location in colorectal cancer: Experience at University Hospital Ramon y Cajal (HURyC) Madrid.

655Background: Adyuvant chemotherapy is a unified therapeutic principle in colon cancer (CC). However, many prognostic factors are arising to determine who really benefits from adyuvant chemotherapy in order to avoid overtreatment. Primary tumor location of CC is emerging as an important prognostic factor owing to distinct biological features. However, there is hardly any evidence showing the benefit of treatment according to primary tumor location. Methods: We retrospectively included patients with stage II and III CC that underwent surgical resection between 2009 and 2014 HURyC. We performed a multivariable Cox model analysis to estimate the benefit of chemotherapy according to tumor location in terms of DFS and OS. The model was further adjusted by including the following confounders: ECOG-PS, number of removed nodes ( < 12 or ≥ 12), use of adyuvant chemotherapy and age. A covariate was considered a confounder factor if the difference between the adjusted and unadjusted coefficient of chemotherapy vari...