Digital Rectal Exams (DRE)

Digital Rectal Exam & Prostate Biopsy

Part 3

In more recent studies, only 26% to 34% of men with suspicious findings on DRE have positive biopsies for cancer (1,2 and 3). So unfortunately the most widely used test for the detection of prostate cancer turns out to be the most subjective. Some factors affecting the results of DRE include: examiners' skills, varied indication for the examination, selection of patients based on symptoms and age, and an increasing suspicion of subtle abnormalities. All these contribute to the wide variability in the sensitivity and specificity of the DRE in cancer detection in men.

Detection rates of 0.8% to 25.0% have been reported, along with PPVs (positive predictive value) of 6.3% to 50.0% (3,4).

In a multicenter prostate cancer screening study of 6,630 men aged 50 years or older, 15% had an abnormal DRE, and one-fifth had cancer diagnosed on sextant biopsy. In this study by Catalona et al. (5), the cancer detection rate was 3.2%, and the PPV of the DRE was 21%. This compares with other studies showing a PPV ranging from 22% to 39% and a detection rate for prostate cancer by DRE ranging from 0.13% to 3.20% (6).

In a series at the University of Washington, carcinoma has been detected in 24 of 185 men (13%) with asymmetry as their only abnormality and 112 of 456 (24.6%) with prostatic induration. In contrast, 79 of 150 (52.7%) with clearly palpable nodules or areas of marked induration strongly suggestive of carcinoma actually demonstrated malignancy (7).

DRE Conclusion

The sensitivity of the DRE in the detection of prostate cancer is low, and the results of this subjective test vary widely with the indication for the examination, selection of patients based on symptoms and age, and clinical experience of the examiner.

Despite the shortcomings of the DRE, in terms of low sensitivity and specificity, up to 25% of prostate cancers are still detected by DRE in men with normal PSA levels. Therefore, a suspicious DRE should be followed by a prostate ultrasound and biopsy, unless it is clinically inappropriate, owing to overall poor patient health. A routine annual DRE is recommended by the American Cancer Society, American Urological Association, and American Medical Association.

Bibliography

1. Thompson IM, Ernst JJ, Gangai MP, et al. Adenocarcinoma of the prostate: results of routine urological screening. J Urol 1984;132:690-692.
2. Chodak GW, Keller P, Schoenberg H. Routine screening for prostate cancer using the digital rectal examination. Prog Clin Biol Res 1988;269:87-98.
3. Lee F, Littrup PJ, Torp-Pedersen ST, et al. Prostate cancer: comparison of transrectal US and digital rectal examination for screening. Radiology 1988;168:389-394.
4. Cooner W, Mosley R, Rutherford CJ, et al. Prostate cancer detection in a clinical urologic practice by ultrasonography, digital rectal examination and prostate specific antigen. J Urol 1990;143:1146-1152.
5. Catalona WJ, Richie JP, Ahmann FR, et al. Comparison of digital rectal examination and serum prostate specific antigen in the early detection of prostate cancer: results of a multicenter clinical trial of 6630 men. J Urol 1994;151: 1283-1290.
6. Bentvelsen FM, Schroder FH. Modalities available for screening for prostate cancer. Eur J Cancer 1993;29a:804-811.
7. Kirby RS, Christmas TJ, Brawer M. Screening for prostate cancer. In: Kirby RS, Brawer MK, Christmas TJ, eds. Prostate cancer. New York: Mosby-Year Book, 1996.
8. Jewett JJ. Significance of the palpable prostatic nodule. JAMA 1956;160:838-839.

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