Purpose: To improve the specificity of cancer detection in patients with normal digital rectal examination and intermediate prostate specific antigen (PSA) level, PSA density has been recommended, with biopsy based on a PSA density of 0.15 or more. PSA density is reportedly higher in Japanese men than in white men, because of physiological differences between the 2 races. We prospectively evaluated PSA density as a discriminator of prostate cancer in Japanese men.
Materials and methods: We evaluated prospectively 60 consecutive men with normal digital rectal examinations and serum PSA levels of 4.1 to 10.0 ng./ml. enrolled during a 17-month period. All patients underwent transrectal ultrasound guided sextant biopsies, regardless of calculated PSA density and transrectal ultrasound findings. Serum PSA levels were determined by IMx assay.
Results: Overall, 8 of 60 men (13%) had prostate cancer. There was no significant difference in mean PSA between those with positive and those with negative biopsies, but the difference was significant in the mean PSA density (mean 0.24 and 0.15, respectively, p < 0.01). Receiver operating characteristics curves for PSA and PSA density demonstrated superior benefit for PSA density in this patient population. A reference PSA density value of 0.19 was chosen because it showed the highest sum of sensitivity and specificity, which gave a sensitivity of 75%, a specificity of 87%, a positive predictive value of 46% and a negative predictive value of 96%.
Conclusions: The results suggest that PSA density improves the specificity of cancer detection in men with a normal digital rectal examination and an intermediate PSA level. Although further study with a larger patient population is needed to obtain a best-fit value, an optimal PSA density cutoff seems to be higher than that recommended in the literature from western countries. Because of possible racial differences in serum PSA and prostate volume, the role of PSA density in Asian men should be studied independently.