Is digital rectal examination (DRE) still considered necessary when screening for prostate cancer?
A 50-year-old healthy farmer was seen for his annual medical by his GP. His family history was significant for breast cancer in his sister. After discussion about risks and benefits of prostate cancer screening he had a digital rectal examination (DRE) which revealed a small firm nodule. His screening PSA was 0.8 ng/ml. I would like to use this case to demonstrate the continued importance and relevance of DRE.
After discussion with the local urologist, the patient had a multiparametric MRI of his prostate which demonstrated a lesion suspicious for malignancy (PIRADS 4) that was confirmed by prostate biopsy to be a Gleason 3+4 (ISUP grade II) prostate cancer.
After further counselling about possible options he underwent robotic bilateral nerve sparing prostatectomy. His final pathology was:
ADENOCARCINOMA, ACINAR, 15% OF EXAMINED PROSTATIC TISSUE, CLEAR MARGINS
GLEASON SCORE 3+3=6, ISUP Group grade 1 (DOMINANT NODULE), minor nodule: 3+4=7 (ISUP Group grade 2) STAGE (AJCC, 7th edition): pT2c
In a healthy 50-year-old man this is considered a significant prostate cancer that would have likely metastasized and shortened his life expectancy if remained untreated. Although PSA testing is generally useful for early detection, it is not always elevated in the setting of prostate cancer as illustrated in this case.
In a nutshell, 10-15% of palpable prostate cancers do not produce enough PSA to be detected by PSA screen testing alone. At the same time a significant proportion of patients with such tumors still benefit from definitive therapy. In my practice, up to 10% of patients undergoing radical prostatectomy have had a normal or very low PSA and they were only detected based on DRE alone which triggered further investigations.
Based on this data, it is highly recommended that DRE accompany PSA testing in men who have been counselled about the risks and benefits of screening and have chosen to be screened for prostate cancer. For the men presenting with lower urinary tract symptoms DRE provides additional information about the size of the prostate that can assist with determining best treatment.
Abdominal/pelvic ultrasound provides information about prostate size but does not help with the detection of abnormalities otherwise palpable on DRE. Multiparametric MRI detects up to 85% of prostate cancers however it is expensive, time consuming and not an ideal screening test and is reserved for further investigation of men already selected by PSA and DRE assessment.