Prostate Cancer May Not be Detected by Digital Rectal Exams Alone

New research suggests that relying on digital rectal exams (DREs) as the primary screening tool for prostate cancer may not be the most effective option. The study comes from Germany and has not yet been published or peer-reviewed, but was presented at the European Association of Urology Annual Congress in Milan in March. Researchers explain that DREs may miss many cancers in earlier stages and are not sensitive enough to detect those early stage cancers. As a result, they recommend using other methods, like prostate-specific antigen (PSA) blood tests and magnetic resonance imaging (MRI), to screen for the disease.

However, in countries like Germany, DREs are the sole method used in a national screening program for prostate cancer, while in the United States, the U.S. Preventive Services Task Force (USPSTF) does not recommend DREs for screenings due to lack of evidence. For the study, researchers investigated data from the PROBASE trial, a German prostate cancer screening study across four different universities in Germany involving 46,495 men who were 45 years old and enrolled between 2014 and 2019. The men were divided into two groups: Half were offered a PSA test immediately at age 45, and the other half were offered a DRE with a delayed PSA blood test at age 50.

The rate of detection using digital rectal exams was substantially lower than other screening options, like PSA, according to the study. PSA testing at 45 years old can find four times more prostate cancers than digital rectal exams. Researchers concluded that widespread use of PSA and MRI would better serve as prostate cancer screening options than digital exams.

The theory behind digital rectal exams is that the prostate sits on top of the rectum, and most prostate cancers grow in the part of the prostate closest to the rectum, making them palpable through the rectum. However, sometimes the changes in tissue may not be pronounced enough to detect with a finger, or the cancer is in a part of the prostate that isn't easily reached through a digital exam. By the time prostate cancer is able to be felt through a digital rectal exam, it may signal later-stage disease. Rashid Sayyid, MD, MSc, Urologic Oncology Fellow of the Prostate Cancer Foundation, University of Toronto, told Health that physical exam features often develop at more advanced stages of local disease, and as such, do not offer the same sensitivity as serum PSA testing in this setting.

Currently, there are no specific guidelines in place for prostate cancer screenings. The U.S. Preventive Services Task Force (USPSTF) recommends that men ages 55 to 69 should make individual decisions about being screened for prostate cancer with a PSA test. Men over 70 should not be routinely screened for prostate cancer. Other organizations, including the American Urological Association (AUA) and the American Cancer Society (ACS), have similar recommendations.

In the U.S., when a person is screened for prostate cancer, “we rely heavily on PSA testing as part of prostate cancer screening, which has resulted in a significant decrease in prostate cancer mortality over the last 30 years,” Preston Sprenkle, MD, a urologic oncologist at Yale Medicine, told Health.

He added that the new study confirms the usefulness of PSA tests, and aims to move Germany’s screening protocols away from using digital exams.

“This study is suggesting that Germany should rely more on blood tests like PSA and not just the digital rectal exam,” Dr. Sprenkle said. “There is a fair bit of data in the U.S. as well that DRE has limited utility as a screening exam and most of our guidelines allow for it but do not specifically recommend its use alone for prostate cancer screening.”

The other upside of using PSA tests for prostate cancer screening: It may open more men up to the idea.

“If the aim of a screening [program] is to pick up cancers as early as possible and the current screening tool isn’t doing that job, then that is a fundamental failure of that approach,” Dr. Albers said in the news release. “We speculate in our paper that not only is the DRE not useful for detecting cancer, but it may also be one reason why people don’t come to screening visits—the examination probably puts a lot of men off.”