Factors Associated With Receipt of Adjuvant Radiation in Locally Advanced Rectal Cancer

Abstract

ABSTRACT Background Neoadjuvant radiotherapy (RT) has been the standard of care for locally advanced rectal cancer (LARC) for over two decades. Adjuvant RT use in LARC represents a deviation from standard care and warrants further investigation. Objectives To identify factors associated with adjuvant RT utilization. We hypothesized that sociodemographic determinants contribute to differences in the sequence of radiation treatment among patients with rectal cancer. Methods This retrospective cohort study utilized the National Cancer Database (2015–2022) to identify adults with clinical stage II–III rectal adenocarcinoma undergoing surgery and RT. Patients were categorized by RT sequence (neoadjuvant vs. adjuvant). Multivariable logistic regression identified factors associated with use of adjuvant RT. Results Of the included 48 452 patients, 6.9% received adjuvant RT. Compared with the neoadjuvant group, adjuvant RT recipients exhibited higher rates of pathologic upstaging (20.5% vs. 10.3%), positive margins (14.7% vs. 6.3%), and lymphovascular invasion (17.4% vs. 11.3%; all p < 0.001). On multivariable analysis, positive margins (aOR 1.78, 95% CI 1.43–2.22), lymphovascular invasion (aOR 1.96, 95% CI 1.66–2.31), upstaging (aOR 1.63, 1.31–2.02) were independently associated with adjuvant RT. Conclusions Adjuvant RT appeared to be used in patients who were found to have high‐risk tumor pathology postoperatively.