11/15/2012 06:17 pm ET

Should I Screen? Study Urges Caution For Cancer Tests

The debate over whether or not routine screening for cancers is an effective preventive treatment has mostly taken place among professionals and government organizations. But what do patients think?

That's the premise of a new study from The Annals of Family Medicine, in which three general practitioners sent surveys to each of their patients, asking them to anticipate the reduced risk of injury or death prevented by various types of screening or preventive medicine: the screening was for breast and bowel cancer and the medication was to reduce hip fracture risk and to prevent further risk factors for cardiovascular disease.

The doctors found that their patients vastly overestimated the benefit of various preventive services: 90 percent overestimated the benefit of mammogram, 94 percent overestimated benefit of colonoscopy, 82 percent overestimated benefit of medication to protect from hip fracture and 69 percent overestimated effect of medication to prevent cardiovascular disease.

What's more, between 32 percent and 41 percent of respondents believed that an 80-year-old who forewent screening was behaving "irresponsibly."

"This tendency to overestimate benefits may affect patients' decisions to use such interventions, and practitioners should be aware of this tendency when discussing these interventions with patients," wrote the researchers.

The 354 patients who participated were between ages 50 and 70 -- ages at which interventions and tests are most likely to occur. While the study took place in New Zealand, surveys of American attitudes show a similar picture.

As Gary Schweizer of Health News Review points out, several studies have showed an outsized enthusiasm for screening as a disease prevention technique. One 2004 study found that 87 percent of surveyed adults believed that screening was always a good idea even though 38 percent had personally experienced a false-positive test.

Currently, the U.S. Preventive Services Task Force , a government panel of experts, recommends against routine prostate cancer screening and advocates a delayed schedule for mammograms. Their position was borne out of clinical data that showed substantial danger associated with unnecessary treatment. For example, in the case of prostate cancer, the task force compared diagnosis and survival rates among populations of men who were routinely screened and those who were not. They found that the difference in survival was negligible, while many of the associated complications from surgical intervention affected men for whom the prostate tumor was not life-threatening.

Detractors point out that many individuals are saved by routine testing, even if the benefit is diminished on a population level. So what's the takeaway from a study like this? The doctors who conducted the New Zealand study recommended that general practitioners can play an important role in discussing the pros and cons of screening among those who are healthy and have no symptoms or family history.