A real-world cohort study reveals the treatment paradox of radiotherapy underuse despite its association with survival advantage

Background: While surgery remains the standard curative treatment for rectal cancer (RC), optimal management for elderly non-surgical RC (ENS-RC) patients is poorly defined. This study aimed to evaluate the real-world utilization and survival association of radiotherapy (RT) in this underserved population, for whom evidence from randomized trials is largely absent.

Methods: We conducted a retrospective cohort study using the Surveillance, Epidemiology, and End Results (SEER) database. To mitigate confounding and selection bias, survival associations were assessed using Kaplan-Meier analysis, multivariable Cox regression, and propensity score matching, supplemented by extensive subgroup and sensitivity analyses.

Results: Among 20,951 elderly ENS-RC patients, 9,019 (43.0%) received RT. After rigorous adjustment for confounders via multivariable Cox regression, RT was consistently associated with improved survival [adjusted hazard ratio (HR) for overall survival (OS) =0.91; 95% confidence interval (CI): 0.87–0.94]. This finding was supported by propensity score matching, which yielded a matched median OS of 16 vs. 13 months and a matched median cancer-specific survival (CSS) of 19 vs. 16 months. Subgroup analyses further confirmed a consistent association across most predefined strata. Particularly, among patients with M0 disease receiving chemotherapy, representing those in better general condition, the survival benefit associated with RT was most substantial (HR =0.73; 95% CI: 0.64–0.83). Notably, patients aged ≥85 years, who had the lowest RT utilization rate (38.2%), exhibited the most pronounced inverse association with mortality (HR =0.74; 95% CI: 0.66–0.82). No significant effect modification by chemotherapy or metastatic status was detected in interaction analyses. The robustness of these primary findings was confirmed through multiple sensitivity analyses.

Conclusions: RT use is associated with a substantial survival benefit in elderly ENS-RC patients, yet it remains underutilized in real-world practice—particularly among the oldest individuals who may benefit most. These real-world findings highlight a potential gap between evidence and practice, suggesting that individualized assessment for RT and further prospective investigation are warranted in this population.