Characterization of prostatic carcinoma among blacks: a comparison between a low-incidence area, Ibadan, Nigeria, and a high-incidence area, Washington, DC.

A comparison of carcinoma of the prostate gland in a low-incidence Nigerian (Ibadan) population and a high-incidence U.S. Afro-American (Washington, D.C.) population was the purpose for this study, initiated in 1973. The frequency of carcinoma (micro- and invasive) was determined in consecutive necropsy cases from hospitals in Ibadan, Nigeria, Accra, Ghana and Washington, D.C. The results of these clinical, epidemiologic and morphologic studies are reported. Clinically, the peak incidence of carcinoma of the prostate in Nigerian males in Ibadan and in American males in Washington, D.C. was in the 65-74 age group. The median age of patients was 66.4 years in Ibadan and 69.2 years in Washington, D.C. Seventy-five percent of Nigerian and 49% of American patients were in stages III and IV. Overall, the distribution by grade of neoplasms in surgical material from Ibadan and Washington, D.C. was similar. Plasma testosterone and estrone levels were significantly higher (p < 0.05 and p < 0.001) in U.S. patients than in U.S. controls and higher (p < 0.001 and p < 0.05) in U.S. patients than in Nigerian patients with prostatic carcinoma. Plasma testosterone levels were significantly lower (p < 0.05) in Nigerian patients than in Nigerian controls. Estrone levels were not significantly different in Nigerian patients than controls. Nigerian patients were more sexually active throughout their lives than American patients; however, they reported a higher incidence of impotence than U.S. patients in the immediate 5 years preceding the diagnosis of prostatic carcinoma. Nigerian respondents (patients and controls) arrived at puberty later than their American counterparts. Within each of the two population groups, the factor with the highest relative risk ratio was lower urinary tract symtoms occurring 10 years or longer before the onset of the present complaints which led to the diagnosis of prostatic carcinoma. Nigerian and U.S. patients were more sexually active than controls. Microcarcinoma (incidental, latent) of the prostate gland occurred with a frequency of 11.8% and at an age-adjusted incidence rate (world standard) of 40.6 per 1000 necropsies in the sampled U.S. black male population. The age-adjusted incidence rate (world standard) for microcarcinoma in the combined West African (Accra and Ibadan) series (36.7/1000) was almost equal to the rate (40.6/1000) in the Washington, D.C. series.