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.