Detecting Prostate Cancer Without Biopsy

Scientists have developed a new way to identify high-risk prostate cancer in men without a biopsy.

Since the prostate-specific antigen (PSA) screening test became widely available, more men are receiving treatment for prostate cancer. However, all patients do not benefit equally from aggressive therapy. Treatment usually begins with a biopsy and can include radiation, surgery, and chemotherapy. The problem is knowing how to tell which men may need aggressive treatment and which men do not. The latter can be closely monitored, sparing them from the effects of treatment.

Researchers at the Oregon Health & Science University Cancer Institute (Portland, OR, USA) teamed up with the Portland Veterans Affairs Medical Center (PVAMC, also in Portland) to find a way to predict which men have lethal prostate cancer before having a biopsy. They have developed a simple chart that urologists and oncologists can use to predict whether a prostate tumor is aggressive, since men with aggressive tumors are more likely to benefit from treatment.

The Gleason score is used to define tumor grade. The score is based on tissue findings throughout the prostate. High scores indicate aggressive cancers, with a score of seven or higher indicating the most lethal cancers. The researchers collected data on 1,669 men with a PSA of less than 10 ng/ml who underwent a prostate biopsy with a minimum of six samples. They analyzed the following variables: age, race, family history of prostate cancer, digital rectal exam, PSA values, PSA density (PSA divided by prostate volume), and prostate volume, PSA doubling time, and ultrasound findings.

Through biopsies, researchers found that almost 92% of the men had no cancer or low-to-moderate cancer graded with Gleason scores between one and six. About one-third of men with prostate cancer had high-grade prostate cancer, detected in 157 patients, or about 9%. Using logistic regression analysis, the researchers compared clinical variables with biopsy outcomes. They found they could accurately predict a tumor's Gleason score by using three clinical variables: age, digital rectal exam findings, and PSA density.

"We found that PSA density is by far the clinical variable most predictive of Gleason score,” noted Mark Garzotto, M.D., lead study investigator. Men who had a PSA density elevated to above 0.18 had a 24-fold greater chance of high-grade prostate cancer than men whose PSA density was low or normal. "Our nomogram identifies the men who are most likely to have high-grade tumors and are most likely to benefit from a biopsy. Knowing a patient's age and the results of a few tests is all the information we need to accurately predict tumor grade without performing a biopsy.”




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