Is prostate cancer screening cost-effective?


Cantor SB, Spann SJ, Volk RJ, Cardenas MP, Warren MM. Prostate cancer screening: a decision analysis. J Fam Pract; June, 1995.

Reviewed by

John Hickner, M.D., M.S.

Clinical question

Is screening men age 50 and over for prostate cancer with digital rectal examination (DRE), transrectal ultrasound (TRUS) and prostate specific antigen (PSA) beneficial?

Background

Screening asymptomatic men for prostate cancer is controversial. Screening advocates cite better survival rates in men with early stage prostate cancer, and doubters point to the lack of either convincing epidemiological data or a controlled trial showing improvement in morbidity or mortality. A definitive controlled trial will take years to complete, and may never be done. In the face of imperfect information, decision analysis is a quantitative analytic method used to determine the optimal clinical strategy. In this review I will use the critique format proposed by Evidence-Based Medicine Working Group to evaluate this prostate cancer screening decision analysis. (1)

Population studied

The decision process is modeled using probabilities of health states and outcomes gleaned from existing scientific literature, combined with the quality of life associated with each outcome on a scale from 0 to 1 (called utilities).

Study design and validity

Were all important strategies and outcomes included? No. The authors confine their model to a single screening strategy; digital rectal exam and PSA, followed by biopsy for a suspicious nodule or positive PSA (10 ng/ml or greater). If the DRE is negative and the PSA is indeterminate (4 to 10 ng/ml) transrectal ultrasound and the predicted PSA (PSA level divided by estimated prostate volume, or PSA density) would be performed to determine if a biopsy would be indicated. This analysis is superior to previous analyses in that a yearly screening strategy is examined. However, a newer screening strategy based on yearly rate of change of age-specific PSA, called PSA velocity, is not included.Was an explicit and sensible process used to identify, select, and combine the evidence into probabilities? Yes. Extensive documentation of probabilities of disease states and outcomes are given. A strength of this analysis was the use of prostate cancer prevalence of clinically detectable lesions, rather than detection of microscopic disease which probably is of little biologic consequence. Five-year survival rates for treated prostate cancer are based on National Cancer Institute data from 1973-86, so these estimates may not be accurate for 1995. Were the utilities obtained in an explicit and sensible way from credible sources? Yes. Ten male patients in their 50's free of prostate disease and their spouses were interviewed using a time-trade-off method to determine quality-adjusted life years for living with the complications of treatment - incontinence, impotence, urethral stricture, rectal injury and gynecomastia. A previous prostate cancer screening decision analysis has been criticized for using physicians' preferences to determine utilities. (4) Using patients is an improvement, but 10 is still a small number, and men in their 60's and 70's were not included. Was the potential impact of any uncertainty in the evidence determined? Yes. Sensitivity analyses were performed to determine if varying the probability and utility parameters in the model affected the preferred strategy.

Outcomes measured

The primary outcome was the cost per quality adjusted life-year.

Results

In the baseline analysis, does one strategy result in a clinically important gain for patients? If not, is the result a toss-up? The preferred strategy favored no screening by a slim margin -- about 6 quality adjusted months. When adverse outcomes of treatment were ignored, screening was the favored strategy, yielding an advantage of 6 unadjusted months. This sounds like a toss-up to me, though clearly patient preference plays a role. Varying the probabilities of disease states and outcomes in the sensitivity analyses did not change the preferred strategy. How strong is the evidence used in the analysis? In general, the analysis is based on fairly good data. The sensitivities and specificities of PSA, DRE, TRUS and biopsy are estimated from published studies, but PSA and TRUS are relatively new tests, and their performance characteristics in population-based screening are not well-established. Outcomes of surgical, radiation, and hormonal treatment of prostate have been described, but, as noted above, current 5-year survival rates may be better than those used in the analysis. Could the uncertainty in the evidence change the result? Yes. If survival is much improved and complication rates decreased by newer methods of treatment, screening might gain a significant advantage. If a new prostate cancer screening test with higher sensitivity and specificity for aggressive prostate cancer is developed, screening may be beneficial. For example, PSA velocity may be superior to the tested strategy.

Recommendations for clinical practice

Will the results help me in caring for my patients? Yes. Despite the current popularity and promotion of PSA screening for prostate cancer, this is the third decision analysis published in the past 3 years showing no clear benefit of screening. (2,3) This analysis confirms my belief that mass prostate cancer screening is not appropriate at this time. Screening (or not!) for prostate cancer should take place only within a doctor-patient relationship where a thorough discussion of the risks and benefits of screening and exploration of patients' preferences can occur. Primum, non nocere.

References

1. Richardson WS, Detsky AS. Users' guides to the medical literature, VII. How to use a clinical decision analysis; Are the results of the study valid? JAMA. 1995;273:1292-5.2. Krahn MD, Mahoney JE, Eckman MH, Trachtenberg J, Pauker SG, Detsky AS. Screening for prostate cancer, A decision analytic view. JAMA 1994;272:773-80.3. Mold JW. Holtgrave DR, Bisonni RS, et al. The evaluation and treatment of men with asymptomatic prostate nodules in primary care: a decision analysis. J Fam Pract 1992;34:561-8.



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