Survival impact of adjuvant chemotherapy in patients with stage IIA colon cancer: Analysis of the National Cancer Database

Utility of adjuvant chemotherapy for stage II cancer remains a matter of debate. Clinical guidelines suggest adjuvant chemotherapy for stage II tumors with high-risk features, in particular T4 tumors. However, limited consensus exists regarding the importance of other high-risk features (lymphovascular or perineural invasion, microsatellite instability). Our study aimed to investigate the impact of adjuvant chemotherapy for stage IIA (T3N0) colon cancer patients. Patients who underwent colectomy for stage IIA colon adenocarcinoma (2010-2015) were identified in the National Cancer Database (NCDB) and divided in two groups based on receipt of adjuvant chemotherapy vs observation. Inverse probability of treatment weighting (IPTW)-adjusted Kaplan-Meier and Cox proportional hazards regression analyses were performed to compare overall survival between the two groups. Subgroup analysis of patients with specific high-risk features LVI, PNI and MSI was performed. Among 46 688 surgical patients with stage IIA colon adenocarcinoma 5937 (12.7%) received adjuvant chemotherapy, while 40 751 (87.3%) were observed. Five-year IPTW-adjusted survival was higher in the adjuvant chemotherapy group (79.7% [95% CI 79.1, 80.2]) compared to the observation group (70.3% [95% CI 69.7, 70.9]). Patients with high-risk pathological features showed an estimated 5-year survival benefit of 11.3% (78.2% [95% CI 77.4, 79.1] vs 66.9% [95% CI 65.9, 67.8]) when treated with adjuvant chemotherapy. This NCDB analysis revealed a survival benefit for patients with stage IIA colon adenocarcinoma and high-risk features that were treated with adjuvant chemotherapy.