Since early prostate cancer typically causes no symptoms, doctors detect the illness by using two common screening methods, the prostate-specific antigen (PSA) test and the digital rectal exam (DRE). This calculator uses those results to predict the likelihood of discovering cancer if you the patient has a biopsy.

PSA is a protein produced by the prostate and normally secreted into the semen. In prostate cancer and certain noncancerous prostate disorders, large amounts of PSA can leak out of the prostate, causing high PSA levels in the blood. In the DRE, the doctor inserts his or her index finger into the rectum and gently feels the surface of the prostate through the rectal wall to check for lumps, hardness and enlargement.

If the PSA level is high or a DRE is abnormal, the doctor may order a biopsy of the patient's prostate. These biopsies generally are performed under the guidance of a transrectal ultrasound. Tissue is taken from the top, the middle and the bottom parts of the gland on both the left and the right side. Biopsies also can be taken from any suspicious areas identified by DRE or ultrasound. If the results of the biopsy confirm the presence of prostate cancer, the laboratory also will assign a Gleason score to the tumor. The Gleason score is an assessment of how abnormal the cancer cells look under a microscope compared to normal prostate cells. The score provides a rough estimate of how likely the cancer is to grow quickly and spread rapidly.

This calculator

This is a mathematical predictive model resulting from a research collaboration between the investigators of the ANNs in CaP Project and investigators from the University of Innsbruck, Austria. Drs. George Bartsch, Wolfgang Horninger, and Helmut Klocker, of the University of Innsbruck, collected data from 3,814 men participating in the Tyrol Screening Project from January 1993 to April 2001. These data were used to develop a clinically useful model that provides estimated probabilities of a positive transrectal ultrasound (TRUS) guided prostate biopsy based on patient age, digital rectal exam (DRE) findings, and baseline serum prostate specific antigen (PSA) level.

Predicted probabilities range from less than 1% to approximately 26%.


Step-wise logistic regression was used to develop the model with a bootstrap validation method. 95% confidence intervals were calculated for each mean probability estimate.


The mean age for the men in the Tyrol Screening database was 63 years and the mean PSA was 9.6 ng/mL. DRE was suspicious in 581 (15.2%). Carcinoma was confirmed by biopsy in 1,022 (26.8%) men.


We have developed a clinically useful model from a large screening database that provides estimates of the probability of finding cancer by TRUS guided biopsy utilizing readily available clinical variables. Such a model can be used by practitioners and patients when assessing diagnostic options.

Study Authors:

Ashutosh Tewari1, E. David Crawford2, George Divine3, Georg Bartsch4, Wolfgang J Horninger4, Eduard J. Gamito2, Mani Menon3, Helmut Klocker4, Colin O'Donnell2.

  1. Vattikuti Urology Institute, Josephine Ford Cancer Center, Detroit, MI and ANNs in CaP Project, Denver, CO
  2. ANNs in CaP Project and University of Colorado Health Sciences Center, Denver, CO
  3. Vattikuti Urology Institute and Josephine Ford Cancer Center, Detroit, MI
  4. Department of Urology, University of Innsbruck, Innsbruck, Austria.


Updated on 17 October 2007