Objective: To create a nomogram for predicting the probability of a positive biopsy in men with one or more previous negative biopsies, as the false-negative rate of prostate biopsy in contemporary series remains substantial, and there is a need to identify those with a negative result but with a high risk of having unrecognized prostate cancer.
Patients and methods: The study included 408 patients from Cleveland Clinic who had one or more repeat biopsies after an initial negative biopsy from 1999 to 2008. Another 470 men with the same criteria were used to validate the nomogram. Nomogram variables included age, family history of prostate cancer, body mass index, findings on a digital rectal examination, prostate-specific antigen (PSA) level, PSA slope, total prostate volume, months from initial negative biopsy session, months from previous negative biopsy, cumulative number of negative cores previously taken and history of high-grade intraepithelial neoplasia or atypical small acinar proliferation. We calculated the nomogram predicted probability in each patient. These predicted outcomes were compared with the actual biopsy results. The area under the receiver operating characteristic (ROC) curve was calculated as a measure of discrimination.
Results: The mean number of previous negative biopsies was 1.5, and the mean number of cores per session was 19.1. Of the original development data, 129 men (31.6%) had prostate cancer. A nomogram was constructed that had a concordance index of 0.72, which was greater than any single risk factor. In the validation group the area under the ROC curve was 0.62.
Conclusions: Our nomogram for predicting a positive repeat biopsy can provide important additional information to aid the urologist and patient with a negative biopsy in evaluating clinical options.
© 2010 DRUG SAFETY RESEARCH UNIT.