Racial influence on the prevalence of prostate carcinoma in Brazilian volunteers

RESUMO

PURPOSE: To investigate the prevalence of prostate carcinoma in a sample of volunteers known to have a large proportion of Bantu African ancestors, and the performance of total PSA (tPSA), PSA density (PSAD) and free-to-total PSA ratio (f/tPSA) on the diagnosis. MATERIALS AND METHODS: A total of 473 volunteers (range 40 - 79 years) were screened for prostate carcinoma. Those with tPSA >2 ng/ml and/or abnormal digital rectal examination were submitted to a transrectal ultrasound-directed biopsy (10 cores). The volunteers were classified as White, Mulatto or Black according to physical characteristics and to ancestors race reference. The following variable number of tandem repeats (VNTR) were analyzed in the blood of 120 volunteers without cancer and in 27 patients with prostate cancer D4S43, PAH, F13A1, APOB and vW-1. RESULTS: The biopsies performed in 121 volunteers revealed cancer in 27 (5.7 percent of 473). The proportions of cancer in White, Mulatto and Black were respectively 0.6 percent (1/148), 6.7 percent (6/90) and 8.5 percent (20/235) (p = 0.006). The VNTRs analysis revealed heterogeneity in White, Mulatto and Black anthropologic phenotypes with the following admixture of Caucasian, African and Amerindian gene lineages 67.5 ± 8 percent, 20.8 ± 8 percent, 11.7 ± 7 percent; 54.8 ± 9 percent, 36.3 ± 5 percent, 8.9 ± 7 percent; and, 45.3 ± 3 percent, 45.9 ± 4 percent, 8.8 ± 7 percent. Such a mixture was 50.5 ± 9 percent, 49 ± 8 percent and 0.5 ± 4 percent in volunteers bearing cancer, and 59.1 ± 7 percent, 31.7 ± 8 percent and 9.2 ± 5 percent in those without cancer. The sensitivity and specificity of tPSA at cut-off levels of 2, 2.5 and 4 ng/ml for volunteers with tPSA <= 10 ng/ml were respectively 100 percent and 6,6 percent, 100 percent and 36,6 percent, 69,2 percent and 62,2 percent. PSAD at a cut-off level of 0.08 or 0.10, and f/tPSA at a cut-off level of 20 percent were able to increase significantly tPSA specificity without loss on sensitivity. CONCLUSIONS: The tumor prevalence was higher in Non-White than in White phenotype. The association of tPSA at a cut-off level of 2.5 ng/ml with a PSAD of 0.08 or a f/tPSA of 20 percent for biopsy indication deserves further investigations as an alternative to tPSA cut-off level of 4 ng/ml.