The study has been published in the journal Cancer.
David Jarrard led the study.
“Anywhere between 30 to 50 percent of apparently low-risk patients actually find out that they have higher-risk prostate cancer after radical prostatectomy and biopsy,” said study principal investigator Dr. David Jarrard, professor of urology in the UW School of Medicine and Public Health.
When prostate cancer is diagnosed, the cancer is graded via the Gleason Score. The score, between 2 (low on the cancer aggression scale) and 10 (highly-aggressive cancer) is determined by looking at cancer cells through a microscope. However, Jarrard says up to half of prostate cancers are upgraded after biopsy.
Jarrard and his team set out to develop a predictive calculation that could more accurately pinpoint cancer aggression before biopsy.
Using more than 30 parameters, Jarrard looked at 413 Gleason 6 cases in which at least 10 cores of the tumor had been evaluated. None of the patients had received therapeutic agents before a main treatment. Clinical variables were collected including age, body mass index (BMI), prostate-specific antigen (PSA), American Urological Association (AUA) symptom score, race, family history of prostate cancer, history of smoking, clinical stage and others.
All patients underwent transrectal ultrasound (TRUS). Several variables were collected including estimated prostate size, biopsy-estimated tumor volume, maximum percentage of core involvement, number of positive cores, total number of cores and other factors. Prostate density or PSAD (per unit volume of prostate tissue) was calculated by dividing PSA by the TRUS-estimated prostate size.
That resulted in development of a model called Biopsy-Integrated Algorithm for Determining Gleason 6 Upgrading Risk (BADGR). The model provides the patient with a percentage assessment for risk of upgrading and is a significant improvement over single variables alone.
Jarrard said that the study shows that factors associated with upgrading of prostate cancer include smaller prostate size, percentage of tumor volume, obesity, higher PSAD, higher number and percentage of positive cores and bilateral disease. In contrast, PSA, smoking history, family history and clinical stage were not predictive of upgrading in prostate cancer.
“We found that PSAD calculated from TRUS-estimated prostate size was one of the strongest independent predictors of upgrading,” said Jarrard.
Jarrard said that while the model improves risk stratification, adding biomarkers into surveillance biopsies will further enhance the ability to identify patients with low-risk prostate cancer.
“Ultimately, the algorithm may be used at time of diagnosis to help a patient decide if active surveillance is enough or if more aggressive treatment is necessary,” said Jarrard.
University of Wisconsin School of Medicine and Public Health