The role of the percentage free PSA in the diagnosis of prostate cancer in Blacks: Findings in indigenous West African men using TRUS guided biopsy

Abstract

Introduction: In Western and Asian literature, the measurement of percentage free prostate specific antigen (%fPSA) has been known to enhance the predictive role of total prostate specific antigen (tPSA) in early prostate cancer (Ca-P) detection. Relationship between the tPSA and Ca-P are known to be influenced by race. To the best of our knowledge, the relationship between %fPSA and Ca-P has not been studied in sub-Saharan Africa using current established biopsy protocol.

Objective: To evaluate the usefulness of %fPSA in indigenous West African men and determine the appropriate cut-off values that may be used as indication for prostate biopsy in men with tPSA of 4–10 ng/ml.

Subjects and methods: A total 169 consecutive patients with tPSA of 4–10 ng/ml with non-suspicious findings on digital rectal examination (DRE) had a transrectal ultrasound (TRUS) guided 10-core prostate biopsy. The technique of PSA analysis was the Access hybritech assay technique using the Beckman’s Access autoimmuno analyser. The rates of prostate cancer in different %fPSA ranges were evaluated. Receiver  operating characteristic curve (ROC) was used to evaluate the efficiency of %fPSA in the diagnosis of prostate cancer.

Results: A reduction %fPSA was associated with a higher detection rate of Ca-P. There was a 62% prevalence of Ca-P with %fPSA ≤ 10% while there was a zero prevalence in patients with fPSA above 20%. At a %fPSA cut off of 20% the sensitivity and specificity were 100% and 45%, respectively. Using the ROC curve, the area under the curve (AUC) was 0.76 while the ROC decision plot showed that a %fPSA cut off 15% was associated with the highest ability to discriminate between benign and malignant diseases.

Conclusion: The %fPSA is an effective discriminating tool in determining the need for prostate biopsy in indigenous West African men with PSA 4–10 ng/ml. A cut off of 15% was associated with the highest performance.

Keywords: Free PSA; West African men; Prostate cancer; Blacks; Nigeria; Lagos