Development of a nomogram that predicts the probability of a positive prostate biopsy in men with an abnormal digital rectal examination and a prostate-specific antigen between 0 and 4 ng/mL.

OBJECTIVES: Early detection of prostate cancer traditionally involves both digital rectal examination (DRE) and serum prostate-specific antigen (PSA) determination in an informed patient population. Abnormalities in either of these studies typically lead to additional evaluations, including prostate biopsy. In this study, we analyzed the operational characteristics of serum PSA between 0 and 4 ng/mL as an initial test for prostate cancer.
METHODS: From January 1990 through May 1997, transrectal biopsies were obtained from 700 men with a serum PSA level less than 4.0 ng/mL but DRE suspicious for cancer. Patient age, race, and serum PSA level were reviewed for this study.
RESULTS: Of the 700 men studied, 445 were white (64%) and 255 were African American (36%). In multivariate analysis of prebiopsy risk factors (age, race, serum PSA), serum PSA was the only independent predictor of a positive prostate biopsy. A nomogram was created that determines the worst-case probability of a positive prostate biopsy in men with PSA between 0 and 4 ng/mL and a DRE suspicious for cancer. The predictions from the nomogram appeared accurate and discriminating, with a bias-corrected area under the receiver operating characteristic curve (i.e., comparison of the predicted probability with the actual outcome) of 0.75.
CONCLUSIONS: Although early detection of prostate cancer has traditionally used both PSA measurement and DRE, PSA testing alone could be more easily implemented and may encourage some men to seek consultation who might not otherwise have done so. By providing a nomogram which provides a worse-case scenario (assuming a positive DRE) of the probability of a positive biopsy, the patient and clinician can make an informed decision as to whether additional evaluation is warranted.