Study scrutinizes role of PSA in predicting prostate cancer risk

Accurate prostate cancer risk-calculation requires more than PSA level to determine the likelihood of prostate cancer.

Issue: June 1, 2006

Prostate-specific antigen (PSA) testing is the primary method used to diagnose prostate cancer in the United States, but research looking at PSA levels after a prostate biopsy has revealed that PSA level is not a very accurate predictor of prostate cancer risk.

Researchers recently published a model to predict prostate cancer risk for men who undergo a prostate biopsy.

PCPT research

Ian M. Thompson, MD, of the University of Texas Health Science Center at San Antonio, and colleagues analyzed 5,519 men aged 55 or older from the placebo group of the Prostate Cancer Prevention Trial (PCPT). Men in the PCPT were followed for seven years. They received regular PSA screening and digital rectal examinations (DREs) annually. If tests were abnormal, men underwent a prostate biopsy. Men also underwent biopsies at the end of the study if they were not biopsied during the study. The researchers used various statistical tests to analyze biopsy results, including family history of prostate cancer, race, age, DRE results and previous biopsy history.

The results showed that prostate biopsy identified cancer in 1,211 men (21.9%). Variables that predicted prostate cancer included higher PSA level, positive family history of prostate cancer and abnormal DRE. A previous, negative prostate biopsy was associated with reduced prostate cancer risk. Neither age at biopsy nor PSA velocity contributed independent prognostic information. Higher PSA level, abnormal DRE, older age at biopsy and being black were predictive for high-grade disease (Gleason score >7), whereas, a previous negative prostate biopsy reduced this risk.

Researchers used their data to develop a risk assessment model that assesses an individual’s risk of prostate cancer. The assessment model is intended for men aged 50 years or older who have no previous history of prostate cancer and who have had recent PSA screening and DRE.

“This risk calculator model uses variables that go beyond only PSA level to help patients and physicians decide whether a prostate biopsy should be performed,” researchers said. “We anticipate that the area of cancer risk modeling, including the incorporation of new risk variables and the understanding of patient decision-making, will have a measurable clinical impact over the next few years.”

This predictive model allows an individualized assessment of prostate cancer risk and risk of high-grade disease for men who undergo a prostate biopsy, according to Thompson and colleagues. Their study was published in a recent Journal of the National Cancer Institute.

Study concerns

In a corresponding editorial, H. Ballentine Carter, MD, of the Johns Hopkins School of Medicine in Baltimore, expressed concern about the false-positive sensitivity of Thompson’s risk calculator.

“In the absence of accurate markers of life-threatening disease, I do not believe that physicians should endorse any approach to predicting the risk of prostate cancer that is likely to increase the diagnosis of biologically unimportant cancers,” Carter wrote in his editorial. “Once we have the ability to assess multiple risk factors (eg, PSA or other new markers) in populations for which the long-term outcomes are known, approaches like the one described by Thompson, et al. will help identify those men who will benefit from active treatment.”

For more information:

Carter HB. Assessing risk: Does this patient have prostate cancer? J Natl Cancer Inst. 2006;98:506-507.

Thompson IM, Ankerst DP, Chen C, et al. Assessing prostate cancer risk: Results from the prostate cancer prevention trial. J Natl Cancer Inst. 2006;98:529-534.