New cutoff point of prostate-specific antigen (PSA) and PSA density (PSAD) to enhance diagnostic specificity for prostate cancer (Pca) in country with low prostate cancer incidence

The purpose of this study is to determine new cutoff point of PSA and PSAD in Indonesia. Three hundred and forty four patients with prostate complain without urinary retention confirmed by biopsies and/or hystopathological examinations were analyzed. There were 332 (96.5%) patients histologically confirmed benign prostate hyperplasia and 12 (3.5%) had prostate cancer (Pea). Using cutoff level for PSA of 4 ng/ml and intermediate value of4.1-10 ng/ml, there were 161 (47%) patients had PSA level less or same as 4 ng/ml and none of them had Pea, 102 (30%) patients had intermediate PSA level (4.1 to 10 ng/ml) and only 1 confirmed Pea (PSA 8.3, PSAD 0.21) while 11 from 81 patients (13.6%) with PSA above 10 ng/ml had Pea. Raising the cutoff point to 8 ng/ml and intermediate value of 8.1-30 ng/ml, from the same group of patients we found 236 (68.6%) BPH patients still with no Pea in PSA less or same as 8.0 ng/ml; 89 BPH patients and 1 Pea in intermediate PSA level, while the rest Pea patients (11 among 18 or 61%) patients) had PSA above 30 ng/ml. We found correlation between mean PSA level with age and prostate volume (p<0.01, r=0.242 & 0.429 in patients with PSA ≤ 4 ng/ml; r=0.265 & 0.452 in PSA ≤ 8 ng/ml, and r-0.261 & 0.020 in PSA > 10 ng/ml). The ability of this new cutoff to enhance the power in detecting Pea was evaluated by using univariate analysis and Receiving Operating Characteristic (ROC) curves. By using new cutoff point produced a sensitivity of 100% in detecting Pea, while specificity is 85.8%. The application of PSAD greater than 0.20 enhanced the specificity to 94.9% and increased the possibility to detect Pea (positive predictive value) from 12.9% to 15%. Area under the curve has also increased from 0.970 to 0.974 for PSA and 0.987 to 0.989 for PSAD compared with standard cutoff points. With the new cutoff level there was a decrease of the number of biopsies up to 42.4% without missing any cancer detection.