A New Prostate Cancer Screening Trial--Anything to See Here?

Kenneth W. Lin, MD, MPH


March 16, 2018

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Hello, everyone. I'm Dr Kenny Lin, a family physician at Georgetown University Medical Center in Washington, DC, and I blog at Common Sense Family Doctor.

The recent publication of the third major randomized trial of prostate-specific antigen (PSA)-based screening for prostate cancer[1] reported no difference in prostate cancer mortality after a median follow-up of 10 years in more than 400,000 men in primary care practices across the United Kingdom. Unlike the US Prostate, Lung, Colorectal, and Ovarian Cancer Screening (PLCO) trial,[2] which also found no benefit, the UK trial evaluated a single invitation to PSA testing, rather than annual screening, and minimal testing occurred in the control group.

My primary care colleagues and I are still waiting for the US Preventive Services Task Force (USPSTF) to finalize its nearly year-old draft recommendation statement on prostate cancer screening, which I characterized in a Medscape commentary as a "surprising reversal." Rather than discouraging PSA screening for men of any age, the USPSTF instead advised that we routinely discuss the potential benefits and harms of screening in men aged 55-69 years and screen men who desire the test. I disagreed with this stance, which I think is analogous to advising clinicians to routinely discuss the potential benefits and harms of antibiotics for viral infections, or the potential benefits and harms of MRI in patients with uncomplicated acute low back pain.

Others are contributing to the PSA debate in the pages of cancer journals, as a recent Medscape article reported. In a position statement[3] published in the Journal of Clinical Oncology, a group of prominent urologists discussed the drop in PSA testing and prostate biopsy rates since 2012 and the rise in the percentage of men diagnosed with prostate cancer presenting with metastatic disease, which began around 2007 but now seems to be rising more sharply. They argued that in contrast to past years, when we were doing too much screening, too little screening is now being done, and they worry that a rise in morbidity and mortality from prostate cancer will follow. In order to get screening "just right," they propose two solutions:

  • For urologists, identifying and validating biomarkers to determine which patients with high PSA levels need prostate biopsy

  • For primary care physicians, "to engage in [more] conversations regarding screening that are individualized and centered on shared decision-making"

I agree that the data show that primary care physicians are doing less PSA testing, but the metastatic prostate cancer statistic, derived from a study of the National Cancer Institute's SEER database,[4] is misleading at best. We know that a substantial proportion of prostate cancers detected by PSA screening are overdiagnosed and would never become metastatic. Less PSA testing means that we are finding fewer of these cancers-in-name-only, so the proportion of all prostate cancers that are metastatic at diagnosis rises as a result. This is likely to be a statistical quirk rather than an early indication that less PSA testing will lead to more deaths.

As for having family physicians do more shared decision-making with men about PSA testing, a commentary in JAMA Oncology[5] by an internist and two oncologists argued that such discussions are a "mirage" in the real world of primary care. The authors asserted that in contrast to guideline recommendations, "the majority of decisions about PSA testing are not shared but made unilaterally by primary care physicians" due to multiple barriers, including time, competing demands, and a dearth of data on how race and family history affect one's risk for clinically important prostate cancer and the benefits and harms of screening. Further, they compared an elevated PSA level to "quicksand," where a cascade of invasive diagnostic interventions with scant supporting evidence can follow in rapid succession and create an unstoppable momentum of their own.

Welcome to my world! Even though few family physicians are as familiar as I with the data and available resources for shared decision-making,[6] most of my patients end up being totally perplexed and either defer the PSA screening decision to a spouse or significant other (who, naturally, wants them to be tested) or say, "Whatever you want to do is fine by me, doc." And in the precious time it takes for us to recognize this shared decision-making mirage, I may miss an opportunity to offer something else that clearly benefits my patient, such as colorectal cancer screening or tobacco-cessation counseling. This tradeoff is a potential harm of shared decision-making that neither the current USPSTF nor academic urologists fully recognize. It is the reason that I persist in telling colleagues and students that the amount of PSA screening that's "just right" should be a lot closer to none at all.

This has been Dr Kenny Lin for Medscape Family Medicine. Thank you for listening.

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