Effect of type of definitive treatment on race-based differences in prostate cancer-specific survival.

BACKGROUND: Racial and ethnic disparities in prostate cancer (PCa) mortality are partially mediated by inequities in quality of care. Intermediate- and high-risk PCa can be treated with either surgery or radiation, therefore we designed a study to assess the magnitude of race-based differences in cancer-specific survival between these two treatment modalities. METHODS: Non-Hispanic Black (NHB) and non-Hispanic White (NHW) men with localized intermediate- and high-risk PCa, treated with surgery or radiation between 2004 and 2015 in the Surveillance, Epidemiology and End Results database were included in the study and followed until December 2018. Unadjusted and adjusted survival analyses were employed to compare cancer-specific survival by race and treatment modality. A model with an interaction term between race and treatment was used to assess whether the type of treatment amplified or attenuated the effect of race/ethnicity on prostate cancer-specific mortality (PCSM). RESULTS: 15,178 (20.1%) NHB and 60,225 (79.9%) NHW men were included in the study. NHB men had a higher cumulative incidence of PCSM (p = 0.005) and were significantly more likely to be treated with radiation than NHW men (aOR: 1.89, 95% CI: 1.81-1.97, p < 0.001). In the adjusted models, NHB men were significantly more likely to die from PCa compared with NHW men (aHR: 1.18, 95% CI: 1.03-1.35, p = 0.014), and radiation was associated with a significantly higher odds of PCSM (aHR: 2.10, 95% CI: 1.85-2.38, p < 0.001) compared with surgery. Finally, the interaction between race and treatment on PCSM was not significant, meaning that no race-based differences in PCSM were found within each treatment modality. CONCLUSIONS: NHB men with intermediate- and high-risk PCa had a higher rate of PCSM than NWH men in a large national cancer registry, though NHB and NHW men managed with the same treatment achieved similar PCa survival outcomes. The higher tendency for NHB men to receive radiation was similar in magnitude to the difference in cancer survival between racial and ethnic groups.