Association of African-American Ethnic Background With Survival in Men With Metastatic Prostate Cancer

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Abstract
Background: African-American men have earlier onset of prostate cancer, higher prostate-specific antigen (PSA) levels, more advanced stage at diagnosis, and higher mortality than white men. It is not known whether the poorer survival of African-American men with prostate cancer reflects their later stage at diagnosis or differences in the basic biology of their disease. To evaluate this question, we examined outcomes of African-American and white men with metastatic prostate cancer in the context of a randomized clinical trial. Methods: Southwest Oncology Group Study 8894 was a randomized phase III trial that compared orchiectomy with or without flutamide in men with metastatic prostate cancer. Using data from 288 African-American and 975 white men in the trial, we conducted a proportional hazards regression analysis to determine if ethnicity was an independent predictor of survival. All statistical tests were two-sided. Results: African-American men were more likely than white men to have extensive disease and bone pain and had poorer performance status, younger age at study entry, higher Gleason score, and higher PSA levels. After adjustment for these prognostic variables, the hazard ratio (HR) for all-cause mortality for African-American men relative to white men was 1.23 (P = .018). Further adjustment for initial quality-of-life assessments also resulted in higher HRs associated with African-American ethnicity relative to white ethnicity (HR = 1.39; P = .007). Conclusions: African-American men with metastatic prostate cancer have a statistically significantly worse prognosis than white men that cannot be explained by the prognostic variables explored in this study. These data should give increased impetus for efforts to detect the disease early in African-American men and for the development of more effective therapies based on potential biologic differences in this ethnic group.