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Performance of the Prostate Health Index for Diagnosis of Prostate Cancer in the Southern African Population

Loretta Svosve, Cuthbert Musarurwa, Hilda T Matarira, Kudakwashe Mhandire, Donald M Tanyanyiwa, South Africa

Background: The 'increasing' incidence of prostate cancer (PCa) globally warrants research and introduction of biomarkers which can accurately reflect disease risk and staging, as well as monitor treatment progress. The widely used total prostate specific antigen (PSA test has shown limitations in PCa detection and classification. Prostate Health Index, one such marker has been successfully introduced into clinical practice in many regions especially in the developed countries. Studies in Africa, particularly in under resourced regions like Zimbabwe are limited. Objectives: The objective of the study was to determine the clinical utility of the PHI in the diagnosis of prostate cancer. Materials and Methods: A cross sectional study was done on 72 men attending a Urology Clinic at Harare Central Hospital and Parirenyatwa Group of Hospitals, both in Harare, Zimbabwe. Inclusion criteria included a tPSA of >2ng/ml and prostate biopsy request. TPSA, % fPSA and -2 pro PSA were determined and biopsy results were documented. Logistic regression models were used to test PCa predictors. Results: PHI had a higher area under the Receiver Operating Curve (AUC=0.824) versus TPSA (AUC=0.524) and %fPSA (AUC=0.808). Prediction of prostate cancer, upon the multivariable analyses, using a base model including age, TPSA and %fPSA the AUC at 95% CI was 0.91 at 95% CI 0.85-0.98). Addition of % [-2] form of proPSA (p2PSA) to the base model increased the AUC to 0.92 at 95 % CI (0.86-0.98). Addition of PHI to the base model increased the AUC to 0.95 at 95% CI (0.91-1.00). PHI detected 29 (83%) cancers out of the 35 aggressive cancers at a cut off of 29.76. Out of the 7 nonaggressive cancers (GS < 7), PHI detected 5 (71%) at a cut-off of 29.76 but missed 2 (29%) and classified them as aggressive. There was no significant correlation between PHI and tumour aggressiveness (p=0.237) Conclusion: To our knowledge, this is the first study to evaluate the clinical utility of the PHI in the sub region. Our findings are in concordance with reports that the PHI is a good marker for the diagnosis of prostate cancer. The cost effectiveness of PHI makes it an ideal biomarker in under resourced settings like Zimbabwe.

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