Use of the Gleason system in international comparisons of prostatic adenocarcinomas in blacks

BACKGROUND. Comparisons of prostate cancer in blacks living in different countries can shed light on factors responsible for high rates of the disease among blacks in America. Since the prognostic value of the Gleason grading system is well established, we assessed agreement between pathologists in countries where black populations of the African Diaspora reside. METHODS. Three genitourinary pathologists at hospitals in Nigeria, Jamaica, and the US independently assessed sextant biopsies from 12 patients. Gleason sum and percentage involvement were recorded, and a percent-weighted average calculated. Agreement under different groupings was evaluated using the kappa statistic generalized to three raters. RESULTS. Agreement was significant for individual sums (kappa=0.3317, P=0.0173), sums grouped as well (2-4), moderately (5-6), and poorly differentiated (7-10) (kappa=0.2437, P<0.0001) and other groupings. Agreement between at least two raters was 91.7-100%; complete agreement was 41.7-66.7%. CONCLUSIONS. The Gleason system is feasible and practical for international studies of prostate cancer among blacks from contrasting environments.