Keeping prevention in perspective: Has the value of screenings been oversold?

Prevention has become a catchword, prompting some experts to question whether physician and patient expectations are realistic.

By Victoria Stagg Elliott — Posted Jan. 26, 2009

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Alfred O. Berg, MD, MPH, believes prevention has been oversold. "As you start looking where the evidence is clear, start doing the math and asking what the actual benefit may be for an individual patient or clinician in practice, it does make you pause," said Dr. Berg, a former head of the U.S. Preventive Services Task Force and professor of family medicine at the University of Washington.

But he also thinks prevention has been undersold. Many interventions, such as vaccinations and smoking cessation, are not advocated enough.

Dr. Berg is part of a small and increasingly vocal group of doctors asking if every preventive medicine strategy -- from screening technology to lifestyle changes -- really can accomplish what physicians and patients hope for and if those that truly are effective get lost in the high volume of prevention messages.

"I don't think that the concept of prevention has been oversold, but there are certainly preventive interventions that have been oversold," said Barnett Kramer, MD, MPH, associate director for disease prevention at the National Institutes of Health.

Scientific evidence documenting a disconnect between what a preventive strategy can achieve versus what is expected is scarce. But many physicians experience the incongruence in daily practice. They also often see patients who have unrealistic perceptions about the degree to which specific health risks may affect them. The few studies that have been done on this subject have, for the most part, involved mammography.

A study in the May 17, 1995, Journal of the National Cancer Institute documented the results of a survey of 145 women 40 to 50 years old. Participants overestimated their risk of dying of breast cancer within the next decade by twentyfold. The relative risk reduction was overestimated sixfold, and the absolute risk by more than a hundredfold.

"We attributed this observation to marketing. The public marketing was so misleading," said William Black, MD, lead author and professor of radiology at the Dartmouth-Hitchcock Medical Center in Lebanon, N.H.

Expectation versus reality

Experts are concerned about such examples -- those in which expectations differ from reality -- because of the potential impact on the doctor-patient relationship. Are patients being scared unnecessarily? Will they take action that could endanger their health in response to test results? Are they being reassured falsely?

"If we promise what we cannot deliver, it's not fair to our patients and it's not fair to us as doctors," said David F. Ransohoff, MD, professor of cancer epidemiology, prevention and control at the University of North Carolina. He has written several papers on the value of colonoscopy.

Concern is particularly high about screenings that can have risks that may not be fully appreciated or balanced by benefits.

"For patients who don't have any symptoms, the chances they have the disease are very low, and the risks become very important," said Dr. Nancy Baxter, associate professor of surgery at the University of Toronto.

Several recent publications support the concept that preventive modalities have significant and important limitations that need to be as well known as the positives.

"Most interventions are a close call and a personal decision. Most people would be surprised to learn that some trials don't show an increase in life expectancy," Dr. Kramer said. "The target population for most interventions are healthy people, and it's difficult to make healthy people better off than they already are. It's a high bar to clear."

For example, reviews of the impact of mammography estimate it reduces breast cancer mortality by about 15%. Some papers put that number as high as 25%, but a study in the Nov. 24, 2008, Archives of Internal Medicine found that women age 50 to 64 who were screened three times over a five-year period had a 22% higher incidence of invasive breast cancer than those screened only once. The authors suspect some of the cancers, had they not been detected with frequent screening, may never have become problematic and may have regressed on their own.

"We just need to be honest that it's a closer call than we have acknowledged," said H. Gilbert Welch, MD, MPH, one of the authors and professor of community and family medicine at Dartmouth Medical School in Hanover, N.H. He is also the author of Should I Be Tested for Cancer? Maybe Not and Here's Why.

Another study, in the Jan. 6 Annals of Internal Medicine, challenged the claim that colonoscopy can prevent as many as 90% of colon cancer deaths. Researchers did a population-based, case-control study in Ontario, Canada, and found that colonoscopy was associated with a 67% reduction in deaths from left-sided colorectal cancer, but only a 1% cut in mortality from the right-sided form.

"Ninety percent is a pretty tall order for any screening test. ... The study demonstrates that colonoscopy is an effective procedure for the prevention of death from colorectal cancer. It just may not be quite as effective as we've thought in the past," said Dr. Baxter, the paper's lead author.

With regard to lifestyle changes, most agree that moderate exercise and weight control are central to overall wellness. The question of the impact of weight loss on mortality rates has been more controversial -- studies result in an array of conflicting findings. Some eating styles also have been linked to a lower risk of various cancers and improved cardiovascular health, but these theories have not always been confirmed in randomized controlled trials.

"Things have been really mixed as to how exercise and diet relate to longevity," Dr. Welch said. "But most people feel better."

Finding a balanced view

Also, physician counseling on these subjects may not translate to improved health outcomes. The USPSTF endorses screening for tobacco use and subsequent counseling, but says evidence is insufficient to encourage primary care physicians to give advice about physical activity and nutrition.

"The question is: In the clinical setting, is it time well-spent for a clinician? The evidence is not strong," said Patrick Remington, MD, MPH, director of the Population Health Institute at the University of Wisconsin School of Medicine and Public Health.

Why expectations for prevention have become so great is not clear, although experts have several theories. Various preventive modalities are heavily promoted by patient organizations, medical societies and public health agencies. The limits of a preventive strategy may get lost as the benefits are emphasized and complex messages get oversimplified in awareness campaigns.

A zeitgeist also emerged in the last century that early detection and lifestyle changes always make a difference. "It just seems like it's the right thing to do," said Russell Harris, MD, MPH, a former USPSTF member and professor of medicine at the University of North Carolina.

In the early 20th century, inventor Thomas Edison predicted, "The doctor of the future will give no medicine, but will interest his patients in the care of the human frame, in a proper diet, and in the cause and prevention of disease." The phrase, "I will prevent disease whenever I can, for prevention is preferable to cure," is part of the modern version of the Hippocratic oath, written in 1964 by Louis Lasagna, MD. Bookshelves, magazine racks and the Internet are full of various publications purporting strategies to save lives. The American Medical Association has many books on the subject, including the American Medical Association Complete Guide to Prevention and Wellness, published in September 2008.

"Prevention should not be abandoned, but there should be a better balance to how we view [it]. There are going to be certain diseases where prevention is going to be better than treatment. The other side of the coin is there are going to be situations where treatment is better than prevention," Dr. Kramer said.

Some physicians say the process for deciding what preventive strategies to pursue is a good fit for shared decision-making to engage patients in understanding various strategies' potential harms and benefits. No one working in this area believes that any of these interventions are inherently bad or dangerous, but many hope to see them applied appropriately.

"When talking about prevention, it's important to put it into context," Dr. Black said. "We should be getting informed consent. ... The person has time to make a deliberate decision. They're not in pain, and there should not be pressure."

But many doctors want to balance the need to be honest about what something can do, with a fear of deterring patients from something that could protect their health.

"I'd hate to discourage women from having a mammogram. There are data that it does some good. It's not perfect, but it's the best we've got," said Carol Lee, MD, head of the American College of Radiology's breast cancer imaging commission.

And many physicians maintain prevention still hasn't been sold enough. After all, enthusiasm for it is high. A study in the Jan. 7, 2004, Journal of the American Medical Association found that 87% of adults felt that routine cancer screening was always a good idea. But that response still doesn't mean everyone is taking part.

"If we have oversold preventive services, smoking rates would not be at 20%. Colonoscopy rates wouldn't be at 40% to 50%, and mammography rates would approach 100%," said Martin Mahoney, MD, PhD, a family physician and director of the cancer prevention and detection center at the Roswell Park Cancer Institute in Buffalo, N.Y.

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What can prevention accomplish?

Mammography for women ages 50-69

  • Risk of breast cancer mortality is cut 15%.
  • Absolute breast cancer risk is reduced by 0.05%.
  • For every 2,000 women invited for screening over a decade, one will have her life prolonged.
  • 10 healthy women will be treated unnecessarily.

Colorectal cancer screening for patients 50 to 75

  • Colonoscopy reduces the risk of colorectal cancer mortality by 60% to 70%.
  • Serious complications occur in an estimated 25 per 10,000 procedures.

Lifestyle changes

  • Physician advice to quit smoking increases the chance of patients who actually do so by 66%.
  • Half an hour of physical activity five days a week decreases the risk of death by 20% to 30%.
  • Physician advice to be more physically active and eat healthier seems to have little if any effect.

Sources: Cochrane Database of Systematic Reviews, Oct. 18, 2006; Annals of Internal Medicine, Dec. 15, 2008; U.S. Preventive Services Task Force recommendations

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External links

U.S. Preventive Services Task Force (link)

Roadmaps for Clinical Practice series: Primer on Population-Based Medicine, American Medical Association, 2002 (link)

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