A national evaluation of the predictors of compliance and survival from adjuvant chemotherapy in high-risk stage II colon cancer: A National Cancer Database (NCDB) analysis.

Background: Guidelines recommend adjuvant chemotherapy for stage II colon cancer with high-risk features, but there has been little study on compliance with guidelines. This work sought to evaluate compliance with adjuvant chemotherapy and factors associated with compliance in high-risk stage II colon cancer. This work's hypothesis was that compliance with adjuvant chemotherapy recommendations is low, but improves overall survival when used.

Methods: The National Cancer Database was reviewed for stage II high-risk colon cancers that underwent curative resection from 2010 to 2017. The cases were stratified into adjuvant chemotherapy and no adjuvant chemotherapy cohorts. A multivariate logistic regression identified factors associated with adjuvant chemotherapy compliance. Propensity-score matching was performed to balance the cohorts and Kaplan-Meier analysis assessed overall survival. The main outcome measures were adjuvant chemotherapy compliance, factors associated with compliance, and overall survival in high-risk stage II colon cancer.

Results: A total of 52,609 patients were evaluated, and 23.2% received adjuvant chemotherapy. The factors associated with noncompliance included older age (odds ratio 0.919; 95% confidence interval 0.915-0.922; P < .001), Medicaid (odds ratio 0.720; 95% confidence interval 0.623-0.832; P < .001) payor, greater comorbidities (odds ratio 0.423; 95% confidence interval 0.334-0.530; P < .001), and residing in the Midwest (odds ratio 0.898; 95% confidence interval 0.812-0.994; P = .037). All of the known high-risk features were significantly independently associated with compliance. In a matched cohort, adjuvant chemotherapy significantly improved the 5-year overall survival (78.1% vs 66.6%; P < .001).

Conclusion: Nationally, there is low compliance with adjuvant chemotherapy in high-risk stage II colon cancer. Despite the low compliance, adjuvant chemotherapy was associated with improved overall survival. Demographic variables were associated with poor compliance, whereas tumor factors were associated with increased compliance. These results highlighted the disparities in care and opportunities to improve outcomes in high-risk stage II colon cancer.