Mediators of racial disparity in the use of prostate MRI.

Abstract

6554 Background: Evidence of racial disparity in the use of prostate MRI presents new obstacles to closing recognized gaps in treatment and outcome for black men with prostate cancer. To anticipate strategies for improving equity in cancer care, we examined mediators of racial disparity in the use of prostate MRI surrounding the diagnosis of prostate cancer. Methods: We conducted a multiple mediation analysis among patients with localized prostate cancer in the Surveillance, Epidemiology, and End Results (SEER)-Medicare database between January 2008 and December 2015. We assessed claims for prostate MRI within the six-month period preceding or following diagnosis. We first identified candidate clinical and sociodemographic meditators based on their association with both race and prostate MRI, including the Index of Concentrations at the Extremes (ICE), a measure of racialized residential segregation calculated at the zip code or census tract level. We used non-linear Multiple Additive Regression Trees (MART) models to estimate the direct and indirect relative effects of mediators. Results: We identified 71,597 eligible patients. Black patients with prostate cancer were less likely (5.3%) to receive a prostate MRI when compared with white patients (7.0%; unadjusted odds ratio 0.75, 95% CI 0.67-0.84, p < 0.001). 33.1% (95% CI 20.6-44.9) of the racial disparity in prostate MRI use was attributable to variation in SEER region, 22.5% (95% CI 13.0-30.2) to residence in a high poverty area, 17.2% to residential segregation (ICE group 17.2%, 95% CI 8.1-27.9%), and 13.2% to dual eligibility for Medicaid (95% CI 8.6-20.2%). Clinical and pathologic factors were not significant mediators. After accounting for the mediators, the direct effects of race accounted for 6.2% of the observed disparity in prostate MRI use. Conclusions: Sociodemographic factors including geographic region, and area-level measures of income and residential segregation explain the majority of the observed racial disparity in the use of prostate MRI among older Americans with prostate cancer. The findings underscore that measurable structural factors can be readily identified that underlie racial disparity in access to emerging diagnostic tools for patients with cancer.