Jay D. Raman, MD
A new study found that, while not 100% accurate, digital rectal examination (DRE) should remain a standard for screening for prostate cancer and may even be able to identify cases of the disease that are not picked up by the prostate specific antigen (PSA) test. The results of the study were reported in The Canadian Journal of Urology
A clinician conducts a DRE by feeling the surface of the prostate with a gloved finger to detect any lumps or hard areas that might be indicative of cancer. The PSA and DRE have been mainstays in screening for the disease, and an abnormal DRE or an elevated PSA test may indicate that a prostate needle biopsy (PNB) is required to diagnose the disease.
“Prostate cancer is the most common cancer in men, accounting for over 28,000 deaths yearly,” said lead author Jay D. Raman, MD, associate professor of Surgery in the Division of Urology at Penn State Milton S. Hershey Medical Center in Hershey, Pennsylvania, in a statement. “Improvements in screening methodology and refinements in cancer care have contributed, in part, to a reduction in recent mortality rates.”
Although previous research has shown that PSA tests are more accurate when predicting the result of a PNB when compared with DRE, no previous study has explored the effectiveness of the DRE compared with PSA when adjusted for age.
In this study, the researchers reviewed the medical charts of 806 men who received an ultrasound-guided PNB between September 2001 and December 2008. Serum PSA levels were considered normal if they fell into specific thresholds based on age (<50 years, PSA <2.5 ng/mL; 51-60 years, PSA <3.5 ng/mL; 61-70 years, PSA <4.5 ng/mL; and >70 years, PSA <6.5 ng/mL). A DRE was categorized as “normal” if the prostate was considered to be smooth, age-appropriate, benignly asymmetric, or uniformly enlarged.
Of the 806 men in the cohort, 516 (64%) had a normal DRE, with the remaining 290 (36%) identified as having an abnormal DRE. Among the entire cohort, 306 men (38%) were diagnosed with prostate cancer, and of those, 136 men (44%) had an abnormal DRE. Of the 136 men with an abnormal DRE and a prostate cancer diagnosis, 43 (31%) had a normal age-specific PSA value according to the thresholds. The authors of the study found no differences in the cancer detection rates when they stratified by the type of abnormality identified with a DRE.
“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.”
The authors concluded that, based on the cohort of patients in this study, an abnormal DRE had a sensitivity of 44%, a specificity of 68%, a positive predictive value of 46%, and a negative predictive value of 67% for detecting prostate cancer on biopsy.
The authors acknowledged that the study had several limitations. In addition to the fact that it is a retrospective analysis, interobserver variability was possible because the DRE status was evaluated by one of five urologists, and the results were limited to one academic medical center, making it unclear as to whether these conclusions are indicative of a larger cohort of similar patients. However, the authors concluded that DRE remains an important part of prostate cancer screening.
“Our study confirms that the digital rectal exam remains an important part of screening such patients because 31 percent of cancers in our study would have been missed by using age-specific PSA cutoffs alone,” Raman said.
Palmerola R, Smith P, Elliot V, et al. The digital rectal examination (DRE) remains important – outcomes from a contemporary cohort of men undergoing an initial 12-18 core prostate needle biopsy. Can J Urol. 2012;19(6):6542-6547.