Survival in Black and non-Black patients with metastatic prostate cancer.

Abstract

101 Background: In the general population, Black men have greater incidence, lower five-year survival, and higher mortality due to prostate cancer when compared to white men. However, in clinical trials and studies of metastatic castrate resistant prostate cancer (mCRPC) in the Veterans Health Affairs (VHA) that excluded chemotherapy, Black men have longer overall survival (OS). We sought to analyze outcomes of Black men treated with androgen receptor targeting agents (ARTAs) abiraterone (AA) and enzalutamide (ENZ) in the VHA. Methods: Patients initially treated with AA or ENZ for mCRPC from May 2011 to June 2017 were identified within the VHA. Racial cohorts of Black and non-Black were determined from patient charts. ANOVA, Kaplan-Meier, and Cox proportional hazards modeling were used to assess the association between overall survival and covariates, including treatment, age, Charlson Comorbidity Index, body-mass index, PSA, year of treatment, prior docetaxel therapy, hemoglobin, creatinine clearance, bilirubin, and albumin at start of treatment. Results: Of 11,027 patients treated for mCRPC with ARTAs, 2550 (23.1%) were identified as Black. Black patients were significantly younger (72.6 vs. 75.8 years, p<0.001), had higher median PSA (60.3 vs. 37.0, p<0.001) and higher Charlson comorbidity index (4.5 vs. 3.9, p<0.001) with lower mean BMI (27.7 vs. 28.4, p<0.001) and higher rates of cardiovascular disease (62.0% vs. 59.8%, p=0.044) and diabetes (45.8% vs. 34.1%, p<0.001). Docetaxel was given more frequently to Black veterans both prior to ARTA (24.7% vs. 16.9%, p<0.001) and at any time (43.1% vs. 31.3%, p<0.001). Black men had a median 2.0 months longer OS than non-Black men (22.0 vs. 20.0, p<0.001) and decreased mortality in unadjusted models (HR 0.89, 95% CI 0.85-0.94) and multivariable models (aHR 0.76, 95% CI 0.72-0.80). Black veterans had longer OS with ENZ compared to AA (24.5 vs. 21.3 months, p<0.001) and decreased mortality (HR 0.83, 95% CI 0.75-0.92) in unadjusted models. However, there was no difference in OS between ENZ and AA in neither multivariable models in all Black men (aHR 0.95, 95% CI 0.85-1.05) nor Black men with cardiovascular disease or diabetes (n=1912, aHR 0.91, 95% CI 0.80-1.03). Conclusions: In the VHA, which provides more equitable access to care, Black men have longer OS with ARTAs compared to non-Black men and increased use of chemotherapy. Importantly, Black men are significantly younger (>3 years) when treated for mCRPC, with higher PSA, and higher rates of comorbid diseases.