Little evidence supports digital rectal exams for prostate cancer screening

Leonard G. Gomella, MD, FACS

The authors focused on the role of the digital rectal exams in screening for prostate cancer in the primary care setting. They performed a comprehensive literature review and determined that the evidence of the utility of the digital rectal exam in prostate cancer screening was lacking.

Screening for prostate cancer has traditionally been done with both digital rectal exam and PSA blood test. Before the widespread use of PSA testing in the late 1980s, the digital rectal exam was the primary prostate cancer screening tool. As the main method to determine who needed a prostate biopsy, the digital rectal exam’s utility to identify early and curable cancer was limited, because the tumor had to be large enough to be palpable. Unfortunately, as the size of the tumor increases so does the likelihood of spread of cancer beyond the prostate. The net result was that before the 1980s most men were diagnosed with advanced disease with a 5-year survival of less than 70%. In 1986, the FDA approved PSA testing to monitor prostate cancer recurrence following definitive therapy. In 1994, PSA testing was FDA approved for men older than 50 years when used along with digital rectal exams to aid the diagnosis of prostate cancer. Today, through a combination of improved screening to detect early disease and advances in treatment, the 5-year survival for prostate cancer is almost 99%, with most men being diagnosed with early stage prostate cancer.

As noted by the authors, it is concerning that medical education is downgrading digital rectal exams as part of the physical exam. Many medical students never perform a digital rectal exam in training and many primary care providers are not comfortable with assessing the exam’s results. There is agreement that the utility of the digital rectal exam in prostate cancer screening has declined with more cancers detected because of PSA with palpably normal glands. However, digital rectal exams are still part of most screening guidelines and there still exists a minority of men who harbor aggressive and palpable prostate cancer with normal PSA. The authors also cite data to support abandoning the digital rectal exam based on the Prostate, Lung, Colorectal, and Ovarian study, where only 2% of men with an abnormal digital rectal exam and normal PSA were diagnosed with significant prostate cancer. However, when combined with both an abnormal digital rectal exam and PSA, 20% had significant prostate cancer vs. an abnormal PSA alone.

The digital rectal exam can also provide other useful information in terms of anorectal pathology and neurologic assessment. For this latter specialty, rectal sphincter tone is often part of a neurological evaluation (lax vs. intact sphincter tone). In urology and neurology, we use the digital rectal exam to test the bulbo cavernous reflex to check if the reflex arc is intact. For the urologist, the digital rectal exam provides critical information concerning prostate anatomy and pathology.

The authors make a strong statement “… although we did not study possible harms of [digital rectal exam], its invasiveness and potential to lead to unnecessary biopsy, overdiagnosis, and overtreatment argue against its routine use.” This is a mantra of those who argue against PSA-based prostate cancer screening and was a major centerpiece of the U.S. Preventive Services Task Force recommendation in 2012 not to screen for prostate cancer. What was missing are the vast improvements in the outcomes in treating localized prostate cancer and the growing use of active surveillance that has reduced the burden of overtreating insignificant disease. The USPSTF is currently re-evaluating the “do not screen” recommendation.

Recognizing the overall PSA screening controversy and the burden often placed on the PCP, we have proposed a new model to consider relying on a PSA referral threshold of 1.5 ng/dL. This PCP urology referral model relies more heavily on the proven utility of PSA. Although the role of the digital rectal exam in prostate cancer detection is not as strong as in the past, caution is needed before we completely abandon the digital rectal exam as a diagnostic and screening tool.

References:

USPSTF. “Draft Recommendation Statement [on] Prostate Cancer: Screening” https://www.uspreventiveservicestaskforce.org/Page/Document/draft-recommendation-statement/prostate-cancer-screening1 (Accessed March 12, 2017)

Crawford ED, et al. Urology. 2016; doi:10.1016/j.urology.2016.07.001.