Role of PSA density in diagnosis of prostate cancer in obese men.

Purpose: To compare the performance of prostate-specific antigen (PSA) density in the diagnosis of prostate cancer in obese and non-obese Chinese men.

Methods: The results of transrectal ultrasound-guided (TRUS) prostate biopsies of Chinese men with PSA <20 ng/mL were reviewed. Parameters including age, body mass index (BMI), TRUS prostate volume, and TRUS biopsy results were recorded. The diagnostic yields of PSA density (>0.15 ng/mL as positive) in obese and non-obese men with PSA <20 ng/mL were compared. Obesity was defined as BMI ≥ 27 kg/m(2) according to WHO recommendation for Hong Kong Chinese.

Results: TRUS biopsy, BMI, and PSA density data were available for 854 men (mean age 65.9 ± 7.3). The mean PSA values for the obese and non-obese patients were 7.9 ± 3.7 and 8.2 ± 4.1 ng/mL, respectively (p = 0.416). TRUS volumes in obese and non-obese men were 63.2 ml and 51.6 ml, respectively (t test, p < 0.001), and PSA density was significantly lower in obese men (0.145 vs. 0.188, p < 0.001). For obese men, positive PSA density was associated with four times (41.1 vs. 9.5 %, p < 0.001) the risk of prostate cancer, compared to only twice the risk (18.8 vs. 9.7 %, p = 0.001) in non-obese men. The specificity and area under the curve of PSA density were 74.2 % and 0.731, respectively, for obese men, and 51.4 % and 0.653, respectively, for non-obese men. Among patients with a diagnosis of prostate cancer, the obese patient group had a significantly higher proportion of patients with Gleason 7-10 prostate cancer than the non-obese patient group (48.9 vs. 32.7 %, Chi-square test, p = 0.035), and a trend toward a higher proportion of bilateral lobe involvement.

Conclusion: PSA density had better performance in obese men. Positive PSA density in obese men was associated with four times the risk of prostate cancer.