A National Evaluation of the Use and Survival Impact of Adjuvant Chemotherapy in Stage II Colon Cancer from the National Cancer Database (NCDB).

BACKGROUND 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. METHODS The NCDB 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, then propensity-score matched. Kaplan-Meier and Cox regression analyzed OS. The main outcome measures were the incidence and impact of AC on OS in low-risk stage II colon cancer. RESULTS Of 39,926 patients evaluated, 8.2% (n=3,275) received AC. Matching resulted 3,275 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 (HR 0.816; 95% CI .713-.934; p<.003). CONCLUSIONS 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.