PROSTATE-SPECIFIC ANTIGEN AS PREDICTOR OF PROSTATE-CANCER IN BLACK-MEN AND WHITE MEN

Background: The increasing incidence of prostate cancer creates complex issues in health care management and cost containment. There is a need to evaluate serial measurements of prostate-specific antigen (PSA) as a marker for long-term risk of clinically important prostate cancer (stages B through D). Purpose: We used a nested case-control design within a retrospective cohort study to evaluate serial PSA concentrations in relation to subsequent prostate cancer diagnoses. Methods: Participants included 40 black and 96 white men with subsequent diagnoses of prostate cancer and 84 black and 100 white men without such diagnoses (control subjects) in a multiphasic health screening program conducted by the Kaiser Permanente Medical Care Program of Northern California. Serial serum samples were collected 1.5-23 years before prostate cancer diagnosis. Results: Median serum PSA concentrations, specific for age and subsequent cancer status, were similar in blacks and whites. Concentrations in control subjects increased exponentially with age, with a doubling time of 24.9 years. Concentrations in men with stage A cancer were similar to those in control subjects. Until about 13 years before diagnosis, PSA in men with subsequent cancer stages B through D increased exponentially with age, with a doubling time similar to that of control subjects. Thereafter, the PSA concentrations increased exponentially, with a doubling time of 4.3 years, Rapid increase in PSA concentration started about 1.5 years earlier for men with stage D cancer than for men with stage B or C cancer. The single PSA measurement drawn closest to diagnosis was a more sensitive marker of stages B through D cancer within the next 7 years than was any index of change that also took account of earlier PSA readings. Conclusions: These data suggest that 1) age-specific PSA concentrations are similar in black men and white men and 2) current PSA concentration, specific for age, outperforms changes in past concentrations in identifying the man who will develop stage B, C, or D cancer within 7 years, albeit at the cost of a slightly higher rate of false-positive results. This interpretation needs confirmation in other data containing many serial PSA measurements within a few years of diagnosis.