Disparate Use of Chemoradiation in Elderly Patients with Localized Anal Cancer

Background: The incidence of squamous cell carcinoma of the anus (SCCA) is increasing, particularly among the elderly (age $65 years). We sought to compare patterns of care for the treatment of SCCA in elderly versus nonelderly patients. Methods: Data for patients with stages I-III SCCA diagnosed from 2004 through 2015 were obtained from the National Cancer Database. Patients were categorized as having received standard-of-care (SOC) chemoradiation (CRT) with multiagent chemotherapy, non-SOC therapy, palliative therapy, or no treatment. Differences in treatment groups were tested using the chisquare test. We used logistic regression to identify predictors of SOC CRT and multiagent versus single-agent chemotherapy in patients receiving CRT. Propensity score matching was used to compare overall survival (OS) in elderly patients receiving multiagent versus singleagent chemotherapy for those receiving CRT. Results: We identified 9,156 elderly and 17,640 nonelderly patients. A lower proportion of elderly versus nonelderly patients (54.5% vs 65.0%; P<.0001) received SOC CRT than other treatments or no treatment. In multivariate analysis, elderly patients were 38% less likely than nonelderly patients to receive SOC CRT (odds ratio, 0.62; 95% CI, 0.58-0.65; P<.0001). A higher proportion of the elderly were treated with single-agent versus multiagent chemotherapy (16.9% vs 11.8%; P<.0001), which resulted in a >1.5-fold increase in the likelihood of elderly patients receiving single-agent chemotherapy (odds ratio, 1.52; 95% CI, 1.39-1.66) in multivariate analysis. After propensity score matching, 3-year OS was higher in elderly patients who received CRT with multiagent versus singleagent chemotherapy (77.1% vs 67.5%; hazard ratio, 0.78; 95% CI, 0.68-0.89; P=.0002). Conclusions: In this comprehensive study of patients with stages I-III SCCA, elderly patients were less likely than nonelderly patients to receive SOC CRT. The low proportion of elderly patients receiving SOC CRT with multiagent chemotherapy for localized anal cancer suggests that the optimal treatment approach for this vulnerable population remains undefined.