Evaluation of diagnostic accuracy of different biomarkers for prostate cancer

Objective: Serum total prostate specific antigen (PSA), free fraction of total prostate specific antigen percent (fPSA %) and prostate specific antigen density (PSAD) have all been considered as valuable non-invasive tumor markers for prostate cancer. This study was carried out to evaluate and compare the performances of serum total PSA, fPSA% and PSAD in terms of their sensitivity, specificity and overall diagnostic accuracy for prostate cancer.

Methodology: Fifty (50) DRE (digital rectal examination)-positive patients admitted in Rajshahi Medical College Hospital (RMCH), Bangladesh during January, 2006 to January, 2008 were included. Estimation of serum total PSA and fPSA% were done by ELISA (Enzyme linked immunosorbent assay) using commercially available kits. Data pertaining to volume of prostate as determined by transabdominal ultrasonography were used to calculate PSAD and histology of the surgically resected prostatic tissue was done for laboratory confirmation of prostate cancer for all patients. Diagnostic sensitivity, specificity and accuracy of serum total PSA, fPSA% and PSAD were calculated using standard formulae against histopathological diagnosis.

Results: Prostate cancer was revealed in 41 of 50 patients by histopathological examination with mean age of 71.2 �10.1 years. There were 9 cases detected as Nodular Hyperplasia of Prostate (NHP) with prostate-specific biomarkers mostly within their normal range. The sensitivity, specificity and overall diagnostic accuracy for prostate cancer of serum total PSA (at cut off value of >10 ng/ml) were 80.48%, 88.90% and 82.00%, for serum fPSA (at cut off value of 0.15 ng/ml/cm3), were found to be 90.00%, 88.90% and 90.00% respectively. Histologically, 27 (65.85%), 13 (31.71%) and 01 (2.44%) cases were labeled as poorly diffentiated, moderately differentiated and well differentiated carcinoma respectively and overwhelming majority had excellent correlation with all prostate-specific biomarkers.

Conclusion: These results reinforce that different prostate-specific biomarkers have good diagnostic prediction with free PSA percent and PSAD have slightly better diagnostic accuracy over serum total PSA for prostate cancer.