The purpose of our SEER analysis was to analyze potential differences in cancer-specific mortality (CSM) between races/ethnicities in metastatic prostate cancer treated with external beam radiotherapy to the prostate. Propensity score matching (3:1) accounted for patient age, prostate-specific antigen, clinical T and N stages, Gleason Grade Groups, and M1 substages between the largest reference group (Caucasians) vs the remaining races/ethnicities: African-Americans, Hispanic/Latinos, and Asians. Other-cause mortality (OCM) adjusted multivariable analyses (competing risks analyses) tested for differences in CSM.