African-American men with low-grade prostate cancer have higher tumor burdens: results from the Duke Prostate Center.

BACKGROUND: To investigate racial differences in tumor burden (cancer volume, cancer percentage and cancer to PSA ratios) in a large cohort of men undergoing radical prostatectomy (RP).
METHODS: Demographic, clinical and pathological data of patients undergoing RP between 1993-2010 were reviewed and compared between African-American (AA) and non African-American (nAA) men. Further assessments of pathological tumor burden (estimated tumor volume, percent of cancer involvement, and estimated tumor volume/PSA ratios) were performed across Gleason score categories.
RESULTS: Of 4157 patients in the analysis, 604 (14.5%) were AA. Overall, AA patients were younger, had higher Gleason scores, PSA levels and incidence of palpable disease (all P < 0.001). Despite comparable prostate weights (39.4 vs. 39.6 g), AA men had higher percent cancer involvement and estimated tumor volume (all P < 0.001) but similar estimated tumor volume/PSA ratios ( P> 0.05). When stratified by Gleason scores, prostate weights were comparable; however, estimated tumor volume, percent cancer involvement and estimated tumor volume/PSA ratios were higher in AA men with low grade (≤ 6) prostate cancer (PCa), similar in intermediate grade (7-8) and lower in high grade (9-10) PCa compared to nAA men.
CONCLUSIONS: In this large series, AA patients had higher disease burden (estimated tumor volume, percent cancer involvement, estimated tumor volume/PSA ratios) compared to nAA but this association was especially pronounced in low grade (Gleason ≤ 6) cancers. These data depict a complex picture of relations between race and tumor burden across the spectrum of PCa aggressiveness. Further investigation is warranted to understand the mechanisms of racial disparities in PCa.