March 9, 2018

There's another controversial PSA test study. Here's how you should think about it.

Daily Briefing

    Read Advisory Board's take on this story.

    One-time prostate-specific antigen (PSA) screening did not significantly reduce mortality rates over a 10-year period, according to a study published in JAMA.

    Study details

    For the study, researchers observed more than 400,000 men between the ages of 50 and 69 who were screened at 573 primary care practices in the United Kingdom. The study began in 2001, and the follow-up concluded in 2016.

    The men were randomly placed in two groups: a test group that received the one-time blood test for PSA, and a control group that did not receive a PSA screening. After a median 10-year follow-up period, 549 of the 189,386 patients who received the PSA test died from prostate cancer, or 0.30 per 100,000 person-years, while 647 of the 219,439 patients who did not receive the PSA test died from the disease, or .31 per 1,000 person-years.

    While both groups saw the same percentage of prostate cancer-related deaths, the researchers found there were more prostate cancer diagnosis in the men who received the PSA test (4.3%) than in those who did not (3.6%).

    The researchers are continuing to monitor the patients for a follow-up analysis.

    Discussion

    In an accompanying editorial, Michael Barry, from Harvard Medical School and Massachusetts General Hospital, who was not involved in the study, wrote, "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. Based on the CAP results, an offer of a single PSA screen in a population of men aged 50 to 69 years is ineffective, and given the higher risk of a prostate cancer diagnosis this approach engenders, likely does more harm than good."

    Richard Martin from the University of Bristol, England, the lead author on the study, concurred, saying that "the findings do not support single PSA testing for population-based screening." One of the biggest problems with the PSA test, according to Martin, is that it "identifies too many low-risk prostate cancers that do not require diagnosis or treatment, while missing some potentially harmful cancers."

    However, William Catalona, a professor of urology at the Feinberg School of Medicine at Northwestern University, took issue with several parts of the study's design, calling the methodology "unrealistic." For instance, he said, "Cancer screening strategies do not rely on a single test performed once to be effective." He also noted that the 10-year follow-up period was "insufficient" to evaluate prostate cancer mortality rates, arguing, "The early trial data underestimate benefits and exaggerate harms" (Mulcahy, Medscape, 3/6; Ingram, MedPage Today, 3/6).

    Advisory Board's take

    Deirdre Saulet

    Deirdre Saulet, Oncology Roundtable

    As mentioned above, it is difficult to draw meaningful conclusions given the design of the CAP study—particularly that the men were screened only one time and were randomly assigned to treatment modality if needed. Nevertheless, this study adds to the ongoing controversy surrounding the benefits and harms of PSA screening.

    In 2017, the U.S. Preventive Services Task Force (USPSTF) updated its stance on PSA screening for men ages 55 to 69. USPSTF went from recommending against the screenings (a stance it had held since 2012) to recommending "individualized decision-making" after such patients consult with their physician. However, critics remain concerned that men and their primary care physicians will forgo meaningful conversations around the risks of PSA screening. In fact, in a phone survey conducted before the latest recommendation of nearly 300 men who had received screening, 64% reported that they had no discussion with a physician about the advantages, disadvantages, or evidence behind PSA screening.

    Health systems need to ensure that providers and their community understand the risks and benefits of PSA screening. To start, organizations should develop screening guidelines that align with their community's needs and providers' preferences. Make sure providers understand the pros and cons of testing, and make it easier for them to identify patients who would benefit from shared decision-making conversations, such as by implementing EHR alerts. Then, host community education sessions to review information on screening and answer questions. It is also critical to provide decision-support tools for providers and patients to guide informed decision-making.

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