Racial differences in prostate-specific antigen levels in patients with local-regional prostate cancer

Prostate-specific antigen (PSA) is a good objective measure of tumor cell burden or virulence of disease, or both, in prostate cancer. Many differences between whites and African Americans (AA) have been noted in prostate cancer in the United States, including a poorer outcome in African Americans. To study whether AAs present with more tumor cell burden or more virulent disease, or both, at presentation, serum PSA levels between whites and African Americans are compared.

Ninety-two patients were seen during April 1988-August 1993 at Albert Einstein Medical Center, Philadelphia; these patients were identified from computer registration records in 1994. Fifty-five patients were AAs and 37 were whites: 14, 55, 15, and 8 had stage A, B, C, or D1 disease, respectively, and 29, 45, and 17 had grade 1, 2, or 3 tumors. Because of positive skewing of actual PSA values, logarithmic transformation was used in statistical analysis. Two sample t-tests and analysis of variance (ANOVA) were used as appropriate.

In univariate analysis, stage (P = 0.043), grade (P = 0.003), and race (P = 0.029) were correlated with the PSA levels; higher-stage and -grade patients and those of African American ethnicity had higher mean PSA levels; type of biopsy and age did not influence PSA levels. On multivariate analysis, race retained its statistical significance (P = 0.05), whereas other factors lost their significance. White patients had 0.51 times lower PSA levels than those of African Americans with comparable stage and grade tumors. Using ANOVA, an average white patient with stage B, grade 1 tumor is likely to have a PSA value of 7.92 ng/ml, compared to 13.9 ng/ml in an African American of similar stage and grade tumor.

The findings of the study confirm previously reported, similar findings in the greater Chicago area. The causes of such racial differences are unknown and require study with individual-level socioeconomic status adjustments, although preliminary studies suggest sociological causes. An ongoing Radiation Therapy Oncology Group (RTOG) study will determine whether such differences exist at the national level and will adjust for individual levels of socioeconomic status.