The outcomes of transrectal ultrasound guided biopsy of the prostate in a New Zealand population.

INTRODUCTION: We aim to produce nomograms relating age, digital rectal examinations (DRE), and prostate specific antigen (PSA) to probability of a positive transrectal ultrasound guided (TRUS) prostate biopsy for a New Zealand population. Usefulness of age-adjusted PSA reference ranges and PSA density are also examined.

METHODS: Data was extracted retrospectively from electronic records of prostate biopsies performed between 1995-2007 in Christchurch, New Zealand. Nomograms were created using logistic regression models. The area under the curve (AUC) for age-adjusted PSA ranges, PSA density, and PSA in predicting a positive biopsy was calculated and used to compare these methods.

RESULTS: 4316 biopsies were available for analysis. Data was incomplete for 1177 (27%) of patients. Biopsy was positive in 54.4%. PSA level and DRE finding were strong predictors of a malignant biopsy in our multivariable model but age was not. PSA level and DRE were also predictors of a higher Gleason score (7 or greater). Nomograms are presented relating PSA and DRE to both a positive biopsy result and to biopsy with Gleason score 7 or greater. AUC for age adjusted reference ranges was no better than PSA using a single cutpoint of 4.0. (0.54 vs 0.53). AUC for PSA density using a cutpoint of 0.15 was 0.72. Receiver Operator Characteristic (ROC) curves showed a clear advantage for PSA density over PSA regardless of cutpoint. (AUC 0.80 vs 0.67).

CONCLUSIONS: Nomograms are formulated to help inform New Zealand men how likely they are to have a positive TRUS prostate biopsy and also how likely they are to have a higher grade cancer detected by TRUS prostate biopsy. Age-adjusted reference ranges did not improve prediction of cancer in this population, but the use of PSA density may enhance prostate cancer diagnosis.