A national evaluation of the use and survival impact of adjuvant chemotherapy in Stage II colon cancer from the national cancer database.

Abstract

Stage II colon cancers are a heterogeneous category, with controversy over use of adjuvant chemotherapy (AC). Patients with high-risk features may benefit from AC to improve overall survival (OS). Current guidelines do not routinely recommend AC in low-risk cases, but the actual use and benefit on OS in this cohort have not been fully examined on a national scale. We aimed to evaluate the use and impact of AC on OS in low-risk Stage II colon cancer. The national cancer database was reviewed for Stage II colon cancers undergoing curative resection (2010-2015). Cases with preoperative radio-chemotherapy or high-risk features were excluded. Cases were stratified into 'AC' and 'no AC' cohorts, and then propensity score matched. Kaplan-Meier and Cox regression analysed OS. The main outcome measures were the incidence and impact of AC on OS in low-risk Stage II colon cancer. Of 39926 patients evaluated, 8.2% (n=3275) received AC. Matching resulted in 3275 cases per cohort. AC significantly improved 1-, 3- and 5-year OS versus no AC (P=0.0017). The 5-year absolute risk reduction was 2.6%, relative risk reduction 12%, with a number needed to treat of 38. In the Cox model, AC remained significantly associated with increased OS (hazard ratio 0.816; 95% CI 0.713-0.934; P<0.003). From this dataset, AC was associated with improved OS in low-risk Stage II disease. These findings from a large-scale sample question current guidelines and the need for better risk stratification. Further study with more robust variables is warranted to determine AC best practices.