The predictive value of PSA in diagnosis of prostate cancer in non screened population

[corrected] PSA is the most important tumor marker in all solid tumor, indispensable in the management of prostate cancer. Screening for prostate cancer is still not recomended, although performed in many countries, which introduced questions about the usefulnes of PSA in detection of prostate cancer. The PSA treshold has also been changed, the value of PSA derivatives revised. Whether such changes are applicable in non scrrened population is questionable. Aim of this study was to evaluate the predictive value of PSA, free/ total PSA and PSA density in our non screened population.

TRUS guided prostate biopsy was performed in 579 patients. The number of cores was 6-12. Mean age of the patients was 67.5 years (30-90). PSA was ranging from 0.41 to 2250 (mean 38.6 ng/ml, median: 11.95, SD 140,45). Digitorectal examination was considered positive in 351 patients. Free PSA was measured in 352 patients with the index ranging from 0.02 to 0.88 (mean free/total PSA: 0.14, median: 0.13). The volume of the prostate was measured in all patients according the prostate ellipsoid model, and PSA density calculated according to the formula PSA/PV. Patients were stratified in 6 groups according to PSA value (I: PSA ng/ml, II: PSA 2.5-4, III: PSA 4-10, IV: PSA 10-20, V: PSA: 20 to 50, Group 6: PSA 50).

Non homogenicity of the patients can be seen through the wide range of PSA which was from 0.4 to 2025). Prostate cancer was diagnosed in 233 pts (40.2%). As expected, the probability of detecting cancer was raised with PSA (p), and was extremely rare in pts with PSA below 4 ng/ml. PSA, free/total PSA, volume of the prostate and PSA density were significantly different according to the presence of cancer. Most of our patients had PSA between 4 and 20 ng/ml. Predictive value of PSA was 20.6% for pts with PSA from 4 to 10 and 32.7% for those with PSA from 10 to 20 ng/ml. Sensitivity, specificity, positive and negative predictive values for different cut off's of PSA (4, 10 and 20) was performed. The best results were obtained for PSA cut off of 10 ng/ml. In the group of patient with PSA, PSA density more reliable than free/total PSA index.

PSA is still valuable marker for detection of prostate cancer in our non screened population. According to our results PSA treshold should not be lowered below 4 ng/ml. PSA density is a reliable PSA derivative, free/total PSA index having less importance in pts with PSA below 20 ng/ml.