Proton Therapy Utilization Among Adult Cancer Patients.

Purpose: Proton therapy (Pr) can spare normal tissue and reduce toxicity; however, it remains a limited resource. The aim of this study was to evaluate demographic and clinical differences in the use of Pr amongst adult cancer patients at a single institution, with particular attention to the impact of insurance coverage. Materials/Methods: Adult patients who underwent radiation between 2015 and 2021 were retrospectively reviewed. Multivariable (MVA) logistic regression analyses were used to assess associations between Pr use and variables including sex, sexual orientation, age, race, ethnicity, marital status, preferred language, smoking status, year of treatment, treatment intent, diagnosis, and distance to facility. Propensity score matching was then used to further validate associations between race and travel distance. Separately, Medicare-insured patients were considered an individual cohort and analyzed utilizing the same demographic variables noted. Results: Of 12,320 patients identified, 2342 and 9978 received Pr and Photon therapy (Ph), respectively. On MVA, Black and Asian race, current smoker, and shorter straight-line distance to the facility remained associated with lower likelihood of treatment with Pr. On propensity-matched scoring, Black patients and patients living within 250 mi of the center remained significantly less likely to receive Pr. Of 4258 Medicare-only patients, 1261 and 2997 received Pr and Ph therapy, respectively. On MVA analysis, female sex, Black race, and decreasing distance to the facility were associated with lower likelihood of receiving Pr therapy Conclusions: We identified significant differences in the use of Pr as a function of distance to site and race in both a heterogeneous adult patient cohort and a Medicare cohort. As health systems expand Pr therapy capacity, understanding how clinico-demographic factors shape access, even under conditions of broad insurance coverage, may inform future infrastructure planning.