Effect of Adjuvant Chemotherapy on Survival Among Patients with Stage IIA Colorectal Cancer Following Radical Surgery: A Propensity Score-Matching Study Using the SEER Database

To explore the effect of adjuvant chemotherapy on the overall survival (OS) and cancer cause-specific survival (CSS) in patients with AJCC stage IIA colorectal cancer. Date of patients with stage IIA colorectal cancer who underwent radical surgery without radical therapy or preoperative chemotherapy were retrieved from the Surveillance, Epidemiology, and End Results database. Propensity score matching (1:1) was performed, yielding a cohort of 14819 patients. The 3-, 5- and 7- year OS rates in the non-chemotherapy group were 80.5%, 50.0% and 16.3%, respectively, compared with 97.2%, 86.0% and 57.3% in the chemotherapy group. Regardless of the risk factors, adjuvant chemotherapy significant improved the OS (<i>p</i> = 0.000), but not for CSS. The Cox proportional-hazards model revealed that age ≥ 65 years, male sex, unmarried status, rectal carcinoma, positive carcinoembryonic antigen, perineural invasion positive, fewer than 12 lymph nodes and multiple cancers were risk factors for both OS and CSS. However, adjuvant chemotherapy was a risk factor only for OS. Regardless of these risk factors or the presence of multiple cancers, adjuvant chemotherapy markedly improved OS in patients with stage IIA colorectal cancer, particularly in those with grade III/IV tumors or fewer than 12 lymph nodes, but has not been proven on CSS.