Racial Discrepancies in Overall Survival among Men Treated with ²²³Radium

Several recent studies on metastatic castration resistant prostate cancer demonstrated improved overall survival in black vs white men. ²²³Radium is Food and Drug Administration approved for metastatic castration resistant prostate cancer based on a survival benefit in the ALSYMPCA (A Phase III Study of Radium-223 Dichloride in Patients with Symptomatic Hormone Refractory Prostate Cancer with Skeletal Metastases) trial, in which 94% of participants were white. We identified a real world population of patients with metastatic castration resistant prostate cancer who received ²²³radium to compare differences in baseline characteristics and outcomes in black vs nonblack men.

We reviewed the charts of all men who received ²²³radium in the entire Veterans Affairs system. We compared treatment patterns and baseline characteristics between black and nonblack men. We used Cox models to analyze predictors of time from ²²³radium start to overall survival and time to skeletal related events.

We identified 318 patients treated with ²²³radium, including 87 (27%) who were black. Median followup after ²²³radium initiation was 25.3 months (IQR 13.8-37.1). Black men were younger than nonblack men when starting ²²³radium (median age 67 vs 70 years, p <0.001) and they had higher prostate specific antigen (median 159.9 vs 90.2 ng/ml, p=0.014) and alkaline phosphatase (median 163 vs 135 IU/l, p=0.017). A greater proportion of black men received docetaxel prior to ²²³radium (77% vs 55%, p <0.001). On multivariable analysis black race was associated with a decreased risk of mortality from the time of ²²³radium initiation (HR 0.75, 95% CI 0.57-0.99, p=0.045).

Black men had longer overall survival than nonblack men, although they appeared to receive radium later in the disease course. Further studies are required to verify our findings and explore biological differences between black and nonblack men with metastatic castration resistant prostate cancer.