PSA TESTING

Prostate cancer is now the second leading cause of death due to cancer in American men.  This is primarily due to improved survival from other diseases and the aging of the American population. The idea of early detection of prostate cancer is intuitively attractive, however there have been some possible objections raised. 

The prevalence of small cancers in clinically “normal” prostates is extraordinarily high.

Small cancers are found at autopsy in the prostate of men at an alarming rate. Every decade of aging nearly doubles the incidence of such tumors—from 10 percent of men in their 50s to 70 percent of men in their 80s. Since it is estimated that there is only a six percent to eight percent chance that a man will have a clinically detected prostate cancer in his lifetime, we can estimate that at least 90 percent of such cancers will remain undetected and clinically unimportant for decades. 

A relatively small percent of prostate cancers are much more aggressive, but there are no screening tests which predict the biologic potential for these tumors and even histology (biopsy) is not a perfect predictor of biologic potential. 

Early detection has classically depended on digital  rectal exam and there is general agreement that men over 50 years of age should have this exam. 

 During the last 10 years serum PSA testing has attracted considerable interest and many urologists are recommending yearly PSA screening for all men over 50 years of age.  They note that the predictive value of PSA for prostate cancer is better than mammography for breast cancer.  PSA’s over 10 should be evaluated by a urologist.  PSA’s between 4 & 10 with a negative rectal exam should be repeated in 6-12 months and if significantly increased, evaluated by a urologist with possible transrectal ultrasound and biopsy.

A Regional Committee on Laboratory Utilization recently asked their chief urologists  for recommendations on screening for prostate cancer.  

A list of pragmatic recommendations showed some interesting results. As a whole, the urologists felt that PSA was not a satisfactory screening test for prostate cancer in asymptomatic men. The current data seemed to indicate that the serum prostate-specific antigen level lacks sufficient specificity, sensitivity, and positive value to qualify it as an accurate test in these cases. Following are their recommendations: 

·PSA should not be used as a screening test for asymtomatic men who are not at significant risk for prostate cancer.

·Men above age 50 should have a digital rectal exam of the prostate as part of their physical exam.

·If the prostate is “suspicious” (asymmetrical, nodular, indurated, hard) in the absence of prostitis, the serum PSA should be determined and the patient referred to a urologist.

·While not recommended, it may be appropriate to perform a rectal exam and obtain a PSA if the patient is concerned about prostate cancer.

Serum PSA above 10 ng/mL is significantly abnormal and these men should be referred to a urologist for evaluation.

·It is unlikely that the discovery of an early  cancer will effect treatment, course or prognosis of men over age 70. PSA determination is strongly discouraged in this age group.

These recommendations reflect this group’s experience, current literature, and the Swedish experience.

The intense debate and sharp differences in opinion on this issue are due, in part, to the lack of good data from well-controlled mass screening studies with minimum 10-year follow-up.  Several studies are now in progress and the National Cancer Institute is contemplating a prospective randomized trial mass screening.                   

The issue is further complicating because there is considerable debate in the literature as to whether early diagnosis and treatment with radical prostatectomy or radiation influences the long-term survival of these patients.   

The only randomized trial comparing radical prostatectomy to no therapy in prostate cancer showed no effect of the treatment on survival. In a Swedish report, a 10-year follow-up on a cohort of  233 men diagnosed with early stage prostate cancer who had no initial therapy.  A subset of these patients met the criteria that would make them eligible, by North American standards, for a radical prostatectomy. The 10-year survival for this subgroup was 87.9 percent. This result is extremely similar to results from published, uncontrolled series of patients treated with modern prostatectomy or radiotherapy. Several other recent articles, including a literature review, a decision analysis modeling, a study of geographic variation and time trends for radical prostatectomy, and an editorial, have also questioned the role of radical prostatectomy.

 Therefore, the only potentially curable treatments for prostate cancer (prostatectomy and radiation) are of questionable efficacy. However, since prostate cancer is a growing cause of death in the American male population, continued efforts can be expected at early detection and curative therapy.