Impact of adjuvant chemotherapy on recurrence risk in stage II colon cancer.

533Background: Although clinical guidelines recommend consideration of adjuvant chemotherapy in high-risk stage II colon cancer, the impact on recurrence risk and cancer related survival is unclear. Furthermore, among Medicare patients, adjuvant chemotherapy was not associated with improved survival. We examine the effect of adjuvant chemotherapy on recurrence risk and overall survival in a diverse cohort. Methods: 6,095 patients who underwent surgery for stage II-III colon cancer (2006-2007) were randomly selected from facilities reporting to the National Cancer Data Base for additional abstraction of tumor information, 5 year recurrence and survival. Death or second cancer within 6 months were excluded. Patients were classified as high or low risk using standard pathologic factors. Multivariate Cox regression with propensity score weighting was performed to compare recurrence risk and overall survival. Results: Of 3,423 patients with stage II colon cancer, 26.9% (n = 883) received chemotherapy compared ...