Medical Device Link.

Originally Published IVD Technology September 2004

INDUSTRY NEWS

Annual prostate cancer screening via PSA test kits, such as the Immulite 2000 by Diagnostic Products Corp. (Los Angeles), will allow practitioners to use PSA velocity to estimate the aggressiveness of malignant tumors.

A rapid increase in prostate-specific antigen (PSA) levels may signal the onset of aggressive forms of prostate cancer. Good news for PSA-test manufacturers.

PSA tests have not have yet reached their true market potential due, in part, to a debate over whether the test is an effective prostate cancer screen or whether it may lead to unnecessary treatment. A study by D’Amico et al. can be used to support the arguments of those in favor of using the test on a regular basis. Published recently in the New England Journal of Medicine, the report sheds light on the importance of the test when used to calculate a patient’s PSA velocity, the rate of rise in PSA levels. 

According to the lead investigator on the study, William J. Catalona, MD, the debate over the PSA test has been fueled by studies “that have been widely misinterpreted by the media as suggesting that the PSA test is no good.” He believes that this study demonstrates that “the PSA test is very valuable for identifying patients at high risk for harboring prostate cancer, for predicting prostate cancer progression after treatment, and for predicting risk for prostate-cancer-specific death.”

The report states that an annual PSA velocity of more than 2.0 ng/ml was associated with a significantly shorter time to death from prostate cancer. The study also suggests that determining the PSA velocity during the year before prostatectomy helps to identify men who may not require immediate treatment and who could be candidates for watchful waiting.

Catalona says, “everybody has been crying for a test that will distinguish between harmless cancer and dangerous cancer. Our study shows that the PSA trend is more important than any single PSA value.”

The authors of an editorial accompanying the article in NEJM are less enthusiastic about the study’s data. “Although the contribution of PSA velocity to the prediction of the risk of death from prostate cancer in poor-risk men is suggestive, the numbers are small, the 95 percent confidence intervals are wide, and the duration of follow-up is relatively short.” The editorial emphasizes the importance of considering other clinical and pathological data along with PSA velocity when identifying aggressive prostate cancer and before determining that a patient is a candidate for clinical trials of aggressive treatment. 

When asked about how the study might affect patient care, Catalona said, “I think it will lead to more-frequent PSA testing and greater attention to changes in PSA levels. PSA testing will begin at an earlier age where there is less confounding from BPH and prostatitis. There will be more testing to see if PSA rises caused by inflammation return to baseline with antibiotic therapy or with time.” 

After reviewing the NEJM article, Diagnostic Products Corp. (DPC; Los Angeles), a manufacturer of PSA assays, conferred with a number of urologists to assess whether the study would impact their clinical practice. 

The majority of the urologists were not surprised by the findings of the study. They were already using serial PSA measurements to calculate PSA velocity and would not use watchful waiting to manage the care of a man whose PSA had increased by 2.0 ng/mL or more in one year. 

However a minority of the urologists, who were not firmly convinced of the value of annual PSA testing before reading the study, stated that the study's results had changed their attitudes towards the test. All of the urologists agreed that the study would likely benefit PSA-test manufacturers.

“If read by the general public, the study's findings could conceivably increase consumer demand for PSA testing by increasing awareness about the importance of PSA testing,” says Jon McDermed, PharmD, the corporate marketing manager for DPC’s tumor marker assays. Heavy coverage of the debate over PSA testing by the lay press makes this prediction likely.

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