Special article
Why is prostate cancer screening so common when the evidence is so uncertain? a system without negative feedback☆

https://doi.org/10.1016/S0002-9343(02)01235-4Get rights and content

Abstract

The degree of enthusiasm for prostate cancer screening seems high given the limited evidence of benefit and the well-documented harms of treatment that include impotence and incontinence. The purpose of this review is to understand the reasons for enthusiasm and positive reinforcement perceived in clinical decisions about whether to screen, whether to choose aggressive therapy for cancer, and in how to view adverse effects following therapy. We discuss a case of a man who must decide whether to undergo prostate-specific antigen screening and treatment to illustrate the kinds of reinforcement that may occur for each decision.

Strong positive reinforcement for each decision would make screening and aggressive therapy appear to be successful and the correct decision even if prostate cancer screening and therapy were not beneficial. A physician is positively reinforced for recommending screening, regardless of the test result, because a negative result makes a patient grateful for reassurance and a positive result makes a patient grateful for early detection. A patient who is impotent and incontinent after a decision for curative treatment may attribute his survival to surgery and be grateful for having his cancer cured. Individual experience provides almost no negative feedback that early detection and aggressive treatment may not work. Although reinforcement operates similarly in other medical decisions, the example of prostate cancer provides insight into the strength of the forces at work because the personal harms, which are relatively common and dramatic, are readily discounted or explained away.

Even if prostate cancer screening is eventually demonstrated to provide benefit for asymptomatic persons, it is important to appreciate the strength of forces that may act independently of benefit and reinforce decision makers’ choices to be aggressive about screening and treatment. Interventions should be considered to temper possible overenthusiasm for screening and treatment.

Section snippets

Decisions in prostate cancer screening and treatment

We illustrate the issues using the case of a man who decides to undergo prostate-specific antigen (PSA) screening and then, after a positive result and diagnosis of cancer, is treated and becomes a survivor who has adverse effects.

Deciding whether to get screened

A 65-year-old otherwise healthy man has asymptomatic prostate cancer that is >0.5 mL in volume, as do almost 10% of men that age (16). He asks his primary care physician about the PSA test because of stories in the media and awareness campaigns sponsored by hospitals, and at the urging of his wife who undergoes routine screening for cancer of the cervix and breast. Friends who have survived prostate cancer also urge him to get screened, as does the U.S. Postal Service, which advocates cancer

Deciding between aggressive therapy and watchful waiting

The patient’s prostate cancer is diagnosed, as it is in more than 180,400 men in the United States each year (20), and is clinically localized, as in approximately 70% of prostate cancers (21). Given a Gleason score of 6 (22), he is offered a choice of radical prostatectomy, external beam radiation, or brachytherapy. The option of expectant therapy is offered to almost no healthy 65-year-old men in the United States with a Gleason score >4 or PSA >4.0 ng/mL 15, 23.

The man chooses radical

Deciding whether adverse effects are acceptable

Despite adverse effects, the patient is happy to be a cancer survivor. Like 90% of men who undergo radical prostatectomy, he says he would definitely or probably make the same choices again. He and his wife are grateful to both the primary care physician and the surgeon, and he urges other men he knows to get screened.

Even the severe adverse effects may be associated with positive reinforcement. Men have a poignant and perhaps paradoxical reaction when asked whether adverse effects were worth

Features of a system lacking negative feedback

For decisions about prostate cancer screening and treatment, the decision to be aggressive is positively reinforced regardless of the outcome. The basic problem is that an individual decision maker cannot assess accurately whether any specific decision produces a successful outcome, while appearances of success may shape the decision maker’s conclusion at every step. People with a negative screening test result are grateful for the result, whereas those with a positive screening test result may

Other examples of systems lacking negative feedback

The phenomenon of drawing erroneous conclusions about the benefit of therapy, based on personal experience, is not new. A patient with a sore throat may believe that penicillin improved the condition. Patients deciding about breast cancer screening and therapy face similar decisions and receive similar positive reinforcement. That the efficacy of breast cancer screening may be supported by stronger evidence than for prostate cancer screening is not the point. The point is that for each of these

The larger environment of decision making

Although our focus is on the positive reinforcement that may occur at each step of decision making about screening and treatment, other forces operate in the larger environment to reinforce decisions for aggressive screening and therapy. Cancer screening and treatment have been promoted by the media, celebrities, and even by the U.S. Postal Service. Cancer has been “militarized” to seem like an enemy that must be defeated at all costs. Screening and therapy occur in an environment with limited

If people are satisfied with aggressive screening and therapy, is there a problem?

If people seem generally satisfied with decisions to be aggressive about screening and therapy, one may ask why we should be concerned. Indeed, part of the problem is that it does not look like there is a problem. If each decision to be aggressive in screening and treatment is positively reinforced, then why meddle with this system? One reason is that the process may, in the long run, lead to net harm. If, in 20 years when more evidence is available, we determine that many more people were

How to intervene

Interventions may be possible at several levels to curb possible overenthusiasm, if there was a public or professional will to do so. At the level of the patient and physician, shared decision making has been promoted. However, it can work only if patients are truly “well informed” (18). According to principles of shared decision making, the decision to not screen would include negative features such as missed opportunity for cure and anxiety about not acting. Positive features of not screening

Acknowledgements

We appreciate the comments of Drs. Michael Barry, Peter Albertsen, Mark Litwin, and Daniel Singer on an earlier version of this manuscript.

References (33)

  • F.J. Fowler et al.

    Patient-reported complications and follow-up treatment after radical prostatectomy. The National Medicare Experience1988–1990 (updated June 1993)

    Urology

    (1993)
  • F.J. Fowler et al.

    Effect of radical prostatectomy for prostate cancer on patient quality of liferesults from a Medicare survey

    Urology

    (1995)
  • J.L. Stanford et al.

    Urinary and sexual function after radical prostatectomy for clinically localized prostate cancerthe Prostate Cancer Outcomes Study

    JAMA

    (2000)
  • J.A. Talcott et al.

    Patient-reported impotence and incontinence after nerve-sparing radical prostatectomy

    J Natl Cancer Inst

    (1997)
  • F.J. Fowler et al.

    Outcomes of external-beam radiation therapy for prostate cancera study of Medicare beneficiaries in three surveillance, epidemiology, and end results areas

    J Clin Oncol

    (1996)
  • A.L. Potosky et al.

    Health outcomes after prostatectomy or radiotherapy for prostate cancerresults from the Prostate Cancer Outcomes Study

    J Natl Cancer Inst

    (2000)

    • Cited by (0)

    ☆

    This study was funded in part by Grant HS 08397 from the Agency for Healthcare Research and Quality (formerly the Agency for Health Care Policy and Research), Rockville, Maryland, to the Patient Outcomes Research Team for Prostatic Diseases. Dr. McNaughton Collins is a recipient of the Doris Duke Clinical Scientist Award. The opinions herein are those of the authors.

    View full text
    Copyright © 2002 Excerpta Medica Inc. All rights reserved.