16 November 2012

Cancer screening patients often overestimate the benefits

Patients asked to estimate how many lives would be saved through cancer screening medication mostly overestimate the benefits of these preventive measures.


Patients asked to estimate how many lives would be saved through cancer screening or how many hip fractures can be prevented with bone-building medication mostly overestimate the benefits of these preventive measures, according to a New Zealand study.

Several hundred patients were asked about the benefits of various cancer screenings and were surprised by how small the benefits actually were, according to findings that appeared in the Annals of Family Medicine.

Doctors, nurses and other medical professionals who communicate health information often don't detail how much a given test or drug can help, but only say that people ought to have it, said Annette O'Connor at the University of Ottawa, who wasn't a part of the study.

"I think it's led to more people taking part in screening or availing themselves of preventive medication than would have been the case if they were presented the information in more meaningful terms," said lead author Ben Hudson, a professor at the University of Otago in Christchurch, New Zealand.

"I would also be concerned that it's led to people having over-heightened expectations of what these things can achieve, and that may lead to disappointment when the inevitable breast cancer happens despite screening."

How the study was done

To get a broader sense of patients' expectations, Hudson and his colleagues asked 354 people about the benefits of breast cancer screening with mammograms, bowel cancer screening with stool testing, taking antihypertension medication and taking bone-strengthening medication.

Specifically, participants were asked to imagine scenarios in which 5 000 people between the ages of 50 and 70 undergo one of these preventive interventions for 10 years, then asked how many "events' they thought would be avoided as a result. For three of the four interventions, the event to be avoided was death. In the case of the bone drugs, it was hip fracture.

For breast cancer screening, only seven percent of the participants answered in the correct range of one to five lives being saved with screening, whereas 80% overestimated how many lives would be saved. Fully a third thought that 1 000 deaths would be averted. The numbers were similar for bowel cancer screening, which is thought to save 5 to 10 lives for every 5 000 people tested.

Eighty-two percent of participants overestimated the number of fractures prevented by bone-strengthening medication, which in reality is about 50 for every 5 000 patients. And 69% of participants reported that 500 or move lives would be saved if 5 000 people took blood pressure medication, when the correct range should have been 50 to 100.

Hudson said that one of the problems that can arise when people overvalue a test is if recommendations for testing are scaled back because of insufficient benefits, people get upset.

In 2009, for instance, when guidelines were changed on regular mammograms from beginning at age 40 to beginning at age 50, a survey of women at the time found that most of them considered the new guidelines to be "unsafe," at least in part because they feared that insurers would no longer cover screening for women in their 40s who wanted it.

"The other thing that happens when you have an established screening program for which people have heightened expectations, it becomes very politically difficult to make any changes insofar as recommending reduced access, even when it is pretty convincing that the outcomes are better," Hudson said.

"I have a feeling this would all be easier if we could present (patients) with this information, trust them with their decisions and support them in doing so," he added.

(Reuters, November 2012)

Read more:

Lung cancer screening can save many

Reasons to go for a mammogram

Cancer - are you at risk?


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