The role of the PCA3 assay in predicting prostate biopsy outcome in a South African setting

Abstract

OBJECTIVES • To evaluate the investigational role, ideal threshold and indications of the Prostate CAncer gene 3 (PCA3) assay in a South African context. • To better define the universality of the above marker since this is the pioneer study on the continent of Africa. PATIENTS AND METHODS • We prospectively evaluated 105 consecutive South African men referred for a prostate biopsy at two tertiary centres in the capital city, Pretoria. • Sequentially, PSA levels and post DRE urine samples were taken within 24 h before prostate biopsy. • The urine specimen was tested using the PROGENSA TM PCA3 assay and a score was generated as (PCA3 mRNA/PSA mRNA)× 1000. • The performance of this assay in predicting biopsy outcome was assessed, and compared with that of serum PSA. RESULTS • Median patient age was 67 years with a positive biopsy incidence of 42.9%. • The higher the PCA3 score the greater the probability of a positive biopsy ( P = 0.003). • This score performed independently of prostatic volume ( P = 0.3889) or the presence of a concurrent primary malignancy ( P = 0.804). • A threshold of 60 revealed a positive predictive value of 60% with an odds ratio of 4, whereas setting a limit of 35 revealed a positive predictive value of 54% and odds ratio of 3.5. • Using receiver operating characteristics for overall performance comparison, the PSA level (area under the curve 0.844) performed better than the PCA3 score (area under the curve 0.705). CONCLUSION • PCA3 assay has shown consistency and performed in line with previous studies but it did not surpass serum PSA in this population. • A PCA3 assay threshold of 60 performed better than the conventional limit of 35. • This assay may have a potential niche in a certain subset of South African men that includes patients with larger glands, previous negative biopsies and altered baseline PSA levels.