Purpose: Although prostate cancer is found in about 30% of patients at the initial biopsy session, there is a need to identify those with a negative result but who are at high risk. Although individual risk factors have been found to be associated with cancer, patient counseling requires the integration of multiple risk factors to obtain a prediction for the individual.
Materials and methods: We studied 343 patients with at least 1 initial negative biopsy who were tested from August 1999 to September 2001. At each biopsy session we recorded patient age, family history of prostate cancer, serum prostate specific antigen (PSA), PSA slope, digital rectal examination findings, months from the initial biopsy session, cumulative number of negative cores previously obtained, and history of high grade prostatic intraepithelial neoplasia or atypical small acinar proliferation. Through Cox regression analysis we determined the association of each variable with time to a positive biopsy. A nomogram was constructed using all variables and discrimination was calculated as the concordance index.
Results: There were 661 biopsy sessions. A mean of 2.9 biopsy sessions were performed per patient and a mean of 9.15 cores were obtained per biopsy session for a mean of 25.2 per patient. Overall 20% of patients had cancer at the second biopsy session. The cumulative number of negative cores obtained, PSA slope, history of high grade prostatic intraepithelial neoplasia and history of atypical small acinar proliferation were associated with repeat biopsy findings (all p <0.05). A nomogram was constructed that had a concordance index of 0.70, which was greater than that of any single risk factor.
Conclusions: We created a nomogram that predicts a positive biopsy after a previous negative biopsy session. It provides a wide range of probabilities for cancer and may improve clinical judgment before the decision to repeat biopsy.