PROSTATE-SPECIFIC ANTIGEN LEVELS ARE HIGHER IN AFRICAN-AMERICAN THAN IN WHITE PATIENTS IN A MULTICENTER REGISTRATION STUDY - RESULTS OF RTOG-94-12

Purpose: To compare serum prostate-specific antigen (PSA) levels in a national sample of African-American and white men with prostate cancer , and to attempt to explain any differences by using self-reported ind ividual-level socioeconomic status adjustments. Methods and Materials: During 4 1/2 months in 1994-95, 709 patients with nonmetastatic prost ate cancer were enrolled in this prospective study; 17.5% were African -American and 82.5% were white. Information about clinical stage, tumo r grade, pretreatment PSA, type of insurance, and educational and inco me status was obtained. Serum PSA levels were measured and racial diff erences were found; how the differences were influenced by other patie nt-or tumor-related factors and if the differences could be explained by socioeconomic status disparities were determined. In univariate ana lyses, factors associated with the mean PSA levels were studied; log-c onverted values were used to yield a normal distribution. Multivariate analyses were done on log-linear models for description of associatio n patterns among various categorical variables; a perfectly fitted mod el should have a correlation value (CV) of 1.0. Results: The mean PSA level was higher in African-Americans (14.68 ng/ml) than in whites (9. 82 ng/ml) (p = 0.001). ClinicaI stage (p = 0.001), Gleason sum tumor g rade (p = 0.0001), educational level (p = 0.001), and household income (p = 0.03) were also associated with mean PSA levels; age, type of bi opsy, and insurance status were not. Disease stage (p = 0.0001), grade (p = 0.0001), education (p = 0.07), and income (p = 0.02) were all as sociated with PSA levels for whites, but none of these factors were im portant for African-Americans (all p values > 0.1). The best fitted lo g-linear model (CV = 0.99) contained PSA (< 10, 10-20, and > 20), Glea son sum grade (2-5, 6-7, and 8-10), race, and two interactions: PSA by race (p = 0.0012) and PSA by Gleason sum (p = 0.0001). Models replaci ng race far either income (CV = 0.82) or education (CV = 0.82) or both (CV = 0.78) did not fit as well. Conclusions: African-Americans with nonmetastatic prostate cancer have higher serum PSA levels at diagnosi s than whites, implying a higher tumor cell burden. Individual-level h ousehold income, education, or insurance status alone or in combinatio n account for racial differences, but only partially. (C) 1998 Elsevie r Science Inc.