Evidence of Benefit
Since PSA assays became widely available in the late 1980s, DRE alone is rarely discussed as a screening modality. A number of studies have found that DRE has a poor predictive value for prostate cancer if PSA is at very low levels. In the European Study on Screening for Prostate Cancer, it was found that if DRE is used only for a PSA higher than 1.5 ng/mL (thus, no DRE is performed with PSA < 1.5 ng/mL), 29% of all biopsies would be eliminated while maintaining a 95% prostate cancer detection sensitivity. By applying DRE only for patients with a PSA higher than 2.0 ng/mL, the biopsy rate would decrease by 36% while sensitivity would drop to only 92%. A previous report from this same institution found DRE to have poor performance characteristics. Among 10,523 men randomly assigned to screening, it was reported that the overall prostate cancer detection rate using PSA, DRE, and TRUS was 4.5% compared with only 2.5% if DRE alone had been used. Among men with a PSA lower than 3.0 ng/mL, the PPV of DRE was only 4% to 11%. Despite the poor performance of DRE, a retrospective case-control study of men in Olmsted County, Minnesota, who died of prostate cancer found that case patients were less likely to have undergone DRE during the 10 years before diagnosis of prostate cancer (OR, 0.51; 95% CI, 0.31-0.84). These data suggested that screening DREs may prevent 50% to 70% of deaths from prostate cancer. Contrary to these findings, results from a case-control study of 150 men who ultimately died of prostate cancer were compared with 299 controls without disease. In this different population, a similar number of cases and controls had undergone DRE during the 10-year interval before prostate cancer diagnosis. One case-control study reported no statistically significant association between routine screening with DRE and occurrence of metastatic prostate cancer.
Rectal examination is inexpensive, relatively noninvasive, and nonmorbid and can be taught to nonprofessional health workers; however, its effectiveness depends on the skill and experience of the examiner. The possible contribution of routine annual screening by rectal examination in reducing prostate cancer mortality remains to be determined.
Transrectal Ultrasound and Other Imaging Tests
Imaging procedures have been suggested as possible screening modalities for prostate cancer. Prostatic imaging is possible by ultrasound, computed tomography, and magnetic resonance imaging. Each modality has relative merits and disadvantages for distinguishing different features of prostate cancer. Ultrasound has received the most attention, having been examined by several investigators in observational settings. Sensitivity ranged from 71% to 92% for prostatic carcinoma and 60% to 85% for subclinical disease. Specificity values ranged from 49% to 79%, and positive predictive values in the 30% range have been reported. The sensitivity and positive predictive value for ultrasound as a single test may be better than for rectal examination. The rate of cancer is extremely low among ultrasound-positive patients in whom rectal and PSA examinations are normal. TRUS is generally relegated to a role in the diagnostic work-up of an abnormal screening test rather than in the screening algorithm. The cost and poor performance of other imaging modalities have led to their elimination from all early detection algorithms.