How Well Does the PCA3-incorporated Chun Nomogram Perform in Predicting Prostate Biopsy Outcome Among South African Men?

The incidence of prostate cancer among South African men is just as significant as it is worldwide [1,2]. Although the role of the prostate cancer antigen 3 (PCA3) assay in predicting biopsy outcome has proven beneficial in a South African context [3], the assessment of its role incorporated into a prostate cancer risk calculator has not yet been explored on the continent of Africa. We aimed to assess the performance of the PCA3-incorporated Chun nomogram [4] and to compare its performance with other contemporary risk calculators. We prospectively evaluated 107 consecutive South African men that were already scheduled for a 13-core transrectal ultrasound prostate biopsy at two referral centres in the South African capital city, Pretoria. The urine PCA3 assay was always performed prior to biopsy and was evaluated using the Progensa assay (Gen-Probe, San Diego, CA, USA). Performance of the following four calculators was compared: • Chun nomogram [4] • Prostate Cancer Prevention Trial (PCPT) risk calculator [5] • Updated (PCA3 incorporated) PCPT risk calculator [5] • European Randomised Study of Screening for Prostate Cancer (ERSPC) risk calculator [6] Histologic evidence of cancer in the prostate biopsy specimen was set as the primary end point. The discriminating ability of each risk calculator was assessed and compared using the concordance index (c-index). The mean patient age was 67 yr. A positive cancer outcome was present in 46 of 107 men, with only 19 of 107 scheduled for a repeat biopsy. Ultimately, 97 patients were assessed because 10 patients were excluded from the comparison data set due to inconclusive PCA3 assay scores (2 of 10) and patient age <55 yr (8 of 10). The four calculators had the following c-indexes: Chun nomogram, 0.93 (95 % confidence interva