Adjuvant chemotherapy in stage 1 colon cancer: Patient characteristics and survival analysis from the national cancer database.

Background: A subset of patients in ACS-NCDB with stage-1 colon cancer received adjuvant chemotherapy (AC), in contrast to national guidelines. This study aimed to define this population and evaluate associations between AC and survival.

Methods: Patients with T1-2N0 colon cancer from 2004 to 2016 were separated into AC and non-AC groups. Adverse pathological features (APF) included T2, poor differentiation, lymphovascular invasion, positive margin, and inadequate lymph nodes (<12). Cox proportional hazard models were used to estimate prognostic factors for overall survival (OS).

Results: A total of 1745 of 139,857 patients (1.2 %) received AC. Receiving AC was associated with male sex (p = 0.02), uninsured (p < 0.01), low income (p = 0.02), or having ≥2 APFs (p < 0.001). In the total cohort, AC was associated with increased mortality (HR 1.14 [1.04-1.24] P < 0.01). On subset analysis, AC was associated with improved OS for patients with ≥2 APFs (log-rank P=<0.001), and decreased mortality when adjusted for covariates (HR 0.81 [0.69-0.95] P=<0.01). The most significant predictor of mortality was old age (HR 3.78 [3.67, 3.89] p ≤ 0.01), followed by higher Charlson Comorbidity Index (HR 1.73 [1.69, 1.76] (p ≤ 0.01), and higher APF score (HR 1.46 [1.42, 15.2] p ≤ 0.01).

Conclusion: AC was associated with decreased survival in the total cohort of stage 1 colon cancer patients, but was associated with improved survival for patients with multiple APFs.