Digital rectal examinations remain important in screening for prostate cancer
The digital rectal examination (DRE) is an important screening test that can discover prostate cancer that a prostate-specific antigen (PSA) test may not, despite the higher sensitivity of the PSA test.
The digital rectal examination is a procedure during which a physician feels the surface of the prostate with a gloved finger. The doctor is able to feel any lumps or hard areas on the prostate. A PSA test checks for levels of PSA in the blood, with higher levels signaling potential cancer. As men age, the acceptable PSA level increases.
"Prostate cancer is the most common cancer in men, accounting for over 28,000 deaths yearly," said Jay Raman, MD, associate professor of surgery at Penn State College of Medicine. "Improvements in screening methodology and refinements in cancer care have contributed, in part, to a reduction in recent mortality rates."
An elevated PSA level or an abnormality found on the prostate during the digital rectal examination typically leads to the recommendation of prostate needle biopsy, the most accurate diagnostic technique. Elevated PSA levels have been shown to more accurately predict a positive cancer biopsy result than the rectal examination. The DRE has been considered less precise because of the variability in who is administering the test and the experience of that person, along with the incorrect positives associated with noncancerous abnormalities.
Other studies have shown the PSA test to be more sensitive and specific than the DRE, especially at low PSA levels. However, no study to the researchers' knowledge had looked at the effectiveness of the digital rectal examination compared with age-adjusted PSA levels.
The researchers studied 806 men from September 2001 to December 2008 to see how the initial testing lined up with the results of their biopsies.
In the group of men studied, half had elevated PSA levels and 36% had an abnormal digital rectal examination (with or without an elevated PSA). The biopsy diagnosed 306 of the men as having prostate cancer. Of that number, 136 of the men had an abnormal DRE finding.
Most importantly, 43 of the 136 men who had abnormal findings on digital rectal examination showed a normal PSA level for their age. While 14% of all patients with prostate cancer had abnormal findings on digital rectal examination, 31% of these men had normal PSA levels for their age.
"It is important to acknowledge that age-specific PSA cutoffs contribute some limitations in prostate cancer screening," Raman said. "In particular, while age-specific thresholds increase the sensitivity in younger men, these same cutoff values lower the sensitivity in older men."
Because the acceptable PSA level is increased for older men, it is possible that prostate cancer is being missed if only the PSA test is used.
"Our study confirms that the digital rectal exam remains an important part of screening such patients because 31% of cancers in our study would have been missed by using age-specific PSA cutoffs alone," Raman said. The findings were published in The Canadian Journal of Urology (2012;19:6542-6547).