Rationale for using serum prostate-specific antigen (PSA) level and PSA density (PSAD) to detect prostatic malignancy in a country with low prostate cancer incidence

Abstract

Prostate-specific antigen (PSA) and PSA density (PSAD) values in Indonesia had been found uniquely much higher than the normal accepted values in western countries. However, PSA more than 10 ng/ml and PSAD above 0.15 in intermediate PSA of 4-10 ng/ml are still indicative of a prostate biopsy. This condition had led to unnecessary biopsies in view of the low incidence of prostatic carcinoma in our country. Our objective is to find alternative serum PSA levels and PSAD cutoff points that enhance the specificity and sensitivity of prostate cancer detection. This retrospective cross-sectional study included 805 consecutive patients from 40 to 95 years old in Sumber Waras Hospital (SWH) and Cipto Mangunkusumo Hospital (CMH) from 1994 to 1997. All patients underwent digital rectal examination (DRE) and transrectal ultrasonography (TRUS) to measure prostate volume. After the serum PSA level was determined and PSAD was calculated, prostate biopsies were performed if the PSA level was greater than 10 ng/ml or PSAD more than 0.15 at intermediate PSA levels of 4-10 ng/ml. The ability of PSA, intermediate PSA level, and PSAD to improve the accuracy of prostate cancer detection was evaluated using univariate analysis. Among 805 patients, 240 patients had PSA level < 4 ng/ml, 230 patients had PSA level 4-10 ng/ml, and 335 had PSA level > 10 ng/ml. Of the 230 patients with intermediate PSA level, 108 had PSAD > 0.15. Thirty-five patients had histologically confirmed prostatic carcinoma, i.e., 3 of 108 patients with PSA 4-10 ng/ml and PSAD > 0.15, and 32 of 335 patients with PSA > 10 ng/ml. There were 105 and 303 unnecessary biopsies in those groups. With a PSA cutoff level of > or = 8 ng/ml, we found 100% sensitivity to prostate cancer. PSAD > or = 0.20 within a PSA level of 8-30 ng/ml gave 100% sensitivity to prostate cancer. Using these new cutoffs there would be 148 biopsies (33.4%) saved. We concluded from this study that the commonly accepted values of serum PSA level and PSAD resulted in many unnecessary biopsies in our patients. Instead, the most sensitive cutoff points to perform prostate biopsy are serum PSA level greater than 8.0 ng/ml, and PSAD of more than 0.20 at an intermediate serum PSA level of 8-30 ng/ml.