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

UNLABELLED: What's known on the subject? and What does the study add? The PCA3 assay has shown significant potential amongst the initial studies carried out in Western countries. This assay performed in line with previous studies. We have shown this marker to perform independent of prostatic volume and have identified potential indications for its use in our setting. However, we have not observed the PCA3 assay to outperform the PSA level across the risk spectrum.

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™ 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.