Even a Single PSA Screening Test Does Not Cut Mortality

Sindings from the latest large randomized controlled study do not support use of even a single prostate-specific antigen (PSA) test for prostate cancer screening. The U.K. study, published March 6 in the Journal of the American Medical Association showed that while the single test screening intervention does detect more prostate cancer cases compared to no screening, testing had no significant effect on prostate cancer mortality after a median followup of 10 years.

Shared Decision Making Not Taking Hold for PSA Testing

Researchers from the American Cancer Society (Atlanta, Ga.) retrospectively analyzed data from 9,598 men aged 50 years and older participating in the 2010 and 2015 National Health Interview Survey in order to assess changes in shared decision making for PSA testing.

In 2017, the U.S. Preventive Service Task Force released updated recommendations, stating that clinicians should inform men (aged 55 to 69 years) about the potential benefits and harms of PSA testing, so that the decision to undergo testing is an individual one.

The researchers found that a similar proportion (about 60 percent) of men with recent PSA testing reported at least one shared decision-making element in 2010 and 2015. However, over the study period, there was a slight shift away from a discussion of only the advantages towards fully shared decision making (discussion of advantages, disadvantages, and uncertainties).

The so-called CAP trial (Cluster Randomized Trial of PSA Testing for Prostate Cancer) is the largest, randomized trial of PSA screening strategies to date and sought to test "a low-intensity strategy" to reduce overdetection of low-risk prostate cancer cases. However, the study did not appear to improve upon previously examined more intense screening strategies tested in the European Randomized Study of Screening for Prostate Cancer and the U.S. Prostate, Lung, Colorectal, and Ovarian Cancer Screening trials.

"The results highlight the multitude of issues the PSA test raises - causing unnecessary anxiety and treatment by diagnosing prostate cancer in men who would never have been affected by it and failing to detect dangerous prostate cancers," said lead author Richard Martin, Ph.D., from University of Bristol (United Kingdom), in a statement.

CAP included 419,582 men aged 50 to 69 years treated at 573 primary care practices across the United Kingdom. Randomization of the practices occurred between 2001 and 2009, with patients followed until March 31, 2016. Practices were randomized to grant men a onetime invitation for PSA testing or not. Men with PSA levels of 3 ng/mL or greater were given a standardized 10-core transrectal ultrasound–guided biopsy.

The researchers found that the proportion of men diagnosed with prostate cancer was higher in the intervention group (4.3 percent) than in the control group (3.6 percent). However, there was no significant difference in prostate cancer mortality between the groups (0.30 per 1000 person-years for the intervention group versus 0.31 for the control group) after a median follow-up of 10 years. Significantly more low-grade prostate cancer tumors (a Gleason grade of 6 or lower) were identified in the intervention group versus the control group (1.7 percent versus 1.1 percent). Furthermore, as a proportion of detected cancers, the prostate cancer tumors in the screening group were significantly less likely to be high grade.

"A key question is whether the findings from the CAP trial should swing the pendulum further in the direction of not offering screening PSA tests," writes Michael Barry, M.D., Massachusetts General Hospital in an accompanying editorial. "Based on the CAP results, an offer of a single PSA screen in a population of men aged 50 to 59 years is ineffective, and given the higher risk of a prostate cancer diagnosis this approach engenders, likely does more harm than good."

Takeaway: Even low-intensity prostate cancer screening with a single PSA test does not cut prostate cancer-related mortality. Additionally, this low-intensity strategy still appears to overdetect low-grade disease.