Radiotherapy Deserts: The Impact of Race, Poverty, and the Rural-Urban Continuum on Density of Providers and the Use of Radiation Therapy in the US

Abstract

Prior efforts to characterize disparities in radiotherapy access and receipt have not comprehensively investigated interplay between race, socioeconomic status, and geography relative to oncologic outcomes. We sought to define these complex relationships at the US county level for prostate (PC) and invasive breast (BC) cancer in order to build a tool that facilitates identification of "radiotherapy deserts"-regions with mismatch between radiotherapy resources and oncologic need. We constructed an ecologic study model using national databases to evaluate 3141 US counties. Radiotherapy resources and utilization densities were operationalized as physician (PPR) and utilization (UPR) per person at risk: number of attending radiation oncologists and Medicare beneficiaries per 100,000 persons at risk, respectively. Oncologic need was defined by "hot zone" counties with ≥2 standard deviations (SD) above mean incidence and death rates. Uni- and multivariable logistic regressions examined links between PPR and UPR densities, epidemiologic variables, and hot zones for oncologic outcomes. Reported statistics are p<.05. Mean (SD) PPR and UPR densities were 2.1 (5.9) and 192.6 (557.6) for PC and 1.9 (5.3) and 174.4 (501.0) for BC, respectively. Counties with high PPR and UPR densities were predominately Metro [odds ratio (OR) 2.9-4.4], generally with higher %Black Non-Hispanic population (OR 1.5-2.3). Incidence and death rate hot zones were largely Non-Metro (OR 0.3-0.6), generally with higher %Black Non-Hispanic constituents (OR 3.2-6.3). Lower PPR density was associated with death rate hot zones for both cancers (OR 0.8-0.9); UPR density was generally not linked to oncologic outcomes on multivariable analysis. Mismatch between oncologic need with PPR and UPR disproportionately affects Non-Metro communities with higher %Black Non-Hispanic population. We developed an interactive web platform (bit.ly/densitymaps) to visualize "radiotherapy deserts" and drive targeted investigation of underlying barriers to care in areas of highest need, with the goal of reducing health inequities in this context.