Evaluation of determinants for age disparities in the survival improvement of colon cancer: results from a cohort of more than 486,000 patients in the United States.

Over the past two decades, elderly colon cancer patients experienced less improvement in survival than their younger counterparts, yet the contributing factors remain unknown. We aimed to evaluate factors that may contribute to the age disparity of survival improvement among patients with colon cancer. Using data from the National Cancer Database, we identified patients diagnosed with colon cancer between 2004 and 2012 with follow-up data up to 2017. The hazard ratios (HR) and 95% confidence intervals (CI) for 5-year OS associated with study variables were estimated using multivariable Cox regression. Among 486,284 patients included in this study, elderly patients (aged ≥75) had a lower adherence to National Comprehensive Cancer Network (NCCN) treatment guidelines (% of non-adherence: 45.3%) than younger patients (aged <50, 19.3%; P<0.001). After adjusting for demographics, access to care and clinical characteristics, compared with patients diagnosed between 2004 and 2006, younger and older patients diagnosed between 2010 and 2012 experienced 16% (HR: 0.84, 95% CI: 0.81-0.88) and 6% (HR: 0.94, 95% CI: 0.93-0.95) reductions in mortality (P for interaction=1.42×10-5), respectively. After an additional adjustment for guideline adherence status, no significant difference in the improvement of survival was noted (P for interaction=0.17). The association patterns were similar regardless of tumor stage, race, and high comorbidity scores (all P for interaction>0.05). Several patient-related factors were identified in association with noncompliance to NCCN guidelines, including comorbidity status. However, over 60% of noncompliance elderly patients had a Charlson comorbidity score of 0. The observed age disparity in survival improvement among colon cancer patients was primarily explained by a slower improvement in adherence to NCCN treatment guidelines in elderly than younger patients. Many older adults were not receiving recommended therapies despite minimal comorbidities. Our findings call for measures to increase adherence to treatment guidelines among elderly patients to improve survival. AJCR