Cancer-screening stats confuse physicians

Physicians don't always correctly interpret efficacy statistics when recommending screening tests to patients, suggests a study published in the Annals of Internal Medicine.

The survey of 412 U.S. primary care physicians revealed that doctors may falsely believe that a high five-year survival rate means that a test saves lives, when in reality, mortality rate is the more relevant statistic.

For the study, participants were presented with two hypothetical scenarios based on real-world prostate cancer data, MedPage Today reported. The first scenario described a test as boosting five-year survival to 99 percent from 68 percent. The majority of the PCPs surveyed--82 percent--incorrectly interpreted this to mean that the test "saves lives from cancer," with 69 percent saying they'd recommend the test. In the second scenario, doctors were told about a test that lowered cancer mortality to 1.6 deaths from 2 per 1,000 people. Just 60 percent of doctors correctly said that the test "saves lives from cancer," with 23 percent saying they'd definitely recommend it.

Several factors likely contributed to physicians' confusion, according to authors Odette Wegwarth, Ph.D., of the Max Planck Institute for Human Development in Berlin, and colleagues. First, although "survival" rates have significant implications in a randomized trial of treatment, physicians may fail to realize its lack of importance when it comes to screening, which automatically increases the length of time a person will live with a diagnosis, MedPage Today noted. In addition, the more eye-catching difference in survival rate numbers, 68 percent versus 99 percent, may have seemed more significant that the seemingly slight mortality rate difference of 1.6 versus 2.

Physicians' answers also indicate they hadn't considered the possibility of overdiagnosis, The Wall Street Journal noted.

In an accompanying editorial, Virginia Moyer, M.D., of Baylor College of Medicine in Houston, said that journal editors and educators should improve the way they present information about screening tests to avoid misinterpretation of results.

To learn more:
- see the study abstract
- read an excerpt of the Annals editorial
- read an article from Reuters
- see a story from MedPage Today
- check out the blog post from The Wall Street Journal