Age, prostate-specific antigen, and digital rectal examination as determinants of the probability of having prostate cancer

Objectives. The decision to perform prostate biopsy has traditionally been based on an abnormal prostate-specific antigen (PSA) level or abnormal digital rectal examination (DRE) findings. For example, a 60-year-old man with a benign DRE and PSA level of 4.1 ng/mL would be counseled for biopsy, and the same man with a PSA level of 3.9 ng/mL might be counseled against biopsy. However, the difference in these PSA levels and in the likelihood of these two men having prostate cancer is not significant. We constructed a probability nomogram for the likelihood of detecting prostate cancer, thus aiding in the decision of whether to perform a prostate biopsy. Methods. Using multivariate logistic regression analysis and data from 2054 men (mean age 64 years) participating in the Tyrol Screening Project between January 9, 1993 and January 9, 1997, patient age, PSA level, and DRE findings were analyzed for their ability to determine the likelihood of finding prostate cancer on transrectal ultrasound-guided biopsy. Results. DRE was suspicious in 278 men (13.5%). Overall, 498 (24.5%) of 2054 men biopsied had prostate cancer. The probability of discovering cancer on biopsy was calculated using patient age, DRE findings, and PSA level. Conclusions. DRE status had a large influence on the likelihood of positive biopsy across all PSA and age ranges. A combination of PSA, DRE result, and age better defined the probability of a positive biopsy than any factor alone. Using this nomogram, the decision to proceed with or defer prostate biopsy can be based on an actual probability of discovering prostate cancer rather than a single PSA-based cutpoint. These data may aid physicians and patients in decision-making.