Early detection of prostate cancer. Part 4
Discussion
Simplified technology has made it feasible for most laboratories in Canada to assay prostate-specific antigen. Very little systematic information is available to suggest any uniformity across different geographic locations in the use of prostate-specific antigen. The volume of PSA testing has increased dramatically in most centres: the volume in our laboratory has doubled in 1 year, from about 250 per month in fall 1993 to 500 per month in fall 1994.
Two randomized, controlled trials are under way to provide the essential information on outcome measures. The European Cancer Program is supporting a study in which asymptomatic adult men will have an initial prostate-specific antigen test and then will be placed (randomly) in a control group or in a screening group in which digital rectal examination and transrectal ultrasound (TRUS) will be performed. The NCI is funding a similar multicentre, randomized trial in which the screening group will be tested with DRE and PSA every 3 years and, if either has abnormal findings, patients will be subjected to TRUS. Initial results from these trials will be available in about 7 years.
The natural progression of prostatic cancer is benign, though not universally so. Routine screening of asymptomatic men with prostate-specific antigen increases the detection rate of prostatic cancers that would not affect the longevity or even the quality of life of many men. However, faced with a diagnosis of cancer, most men opt for surgery or radiation therapy rather than take the chance that their cancer will not advance. In spite of improved surgical techniques, postoperative complication rates of impotence and urinary incontinence are high.
Wasson et al have reviewed the literature from 1982 to 1992 and give the following mean complication rates for total prostatectomy: incontinence 26.6%, impotence 85%, impotence following nerve-sparing surgery from two series 32%. Complication rates were slightly lower with radiation therapy. Most of these men (who had localized prostatic cancer) were symptom free, but must now live with complications for the rest of their lives. Chodak worked out the average mortality after radical prostatectomy (from reports published in academic centres) to be 1%, with a range of 0.5% to 3.0%.
Conclusion
Use of prostate-specific antigen for early detection of prostatic cancer is not supported by scientific evidence at present, and risk-to-benefit analysis is incomplete. If early detection of prostatic cancer is discussed during a periodic physical examination of a man between 50 and 70 years, some of these salient points should be brought up. If a decision is made to evaluate the prostate, do a PSA test and a digital rectal examination; if not, neither prostate-specific antigen nor DRE need be done.
Genitourinary symptoms and family history of prostatic cancer strongly indicate that a prostate-specific antigen test and a digital rectal examination should be done. If PSA levels are abnormally elevated, if patients have urinary symptoms requiring surgical evaluation, or if DRE findings are suspect, patients should be referred to urologists for further evaluation. ■