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Survival Data Versus Mortality Rates
Survey Suggests Physicians May Have Difficulty Interpreting Cancer Statistics
By Lisa Curran
The researchers reported that 76 percent of primary care physicians surveyed indicated that survival data prove that screening saves lives. About one-half of the physicians also said that finding more cancer cases in screened versus unscreened populations proved that screening saves lives.
According to the National Cancer Institute, however, because survival and early detection rates are susceptible to lead-time and overdiagnosis biases, while mortality rates are not, reduced mortality is the only statistic that reliably proves the benefit of cancer screening.
The results come as no surprise to Doug Campos-Outcalt, M.D., chairman of the Department of Family, Community and Preventive Medicine at the University of Arizona College of Medicine, Phoenix, and the AAFP liaison to the U.S. Preventive Services Task Force. It's a problem, he said, that most likely extends to other types of physicians and throughout society.
"It's not just doctors," Campos-Outcalt told AAFP News Now. "It's newspaper reporters. It's organizations. I've argued with congressmen over this sort of thing."
- Many primary care physicians misinterpret cancer screening statistics, according to a recent survey.
- The National Cancer Institute says reduced mortality is the only statistic that reliably proves that cancer screening saves lives.
- Society at large overestimates the need for cancer screening, exacerbating the risks of overtesting and overtreatment.
"This is an inability to really grasp numbers and analyze the true numbers," Campos-Outcalt said. "You have a lot of physicians practicing who were never trained in this." All the more reason, he added, for physicians to "look to organizations that know how to analyze the evidence and make solid, evidence-based recommendations, such as the U.S. Preventive Services Task Force."
For his part, Campos-Outcalt said he takes pains to emphasize these concepts in the classroom, and he thinks that most medical schools now teach students these concepts and point out these kinds of errors.
"I think it's going to be less of a problem as time goes on and this becomes more ingrained in medical school curricula," he said.
When it comes to patients' views on screening for cancer, however, the idea that it's not always the best course may be a hard sell.
In an editorial accompanying the research (excerpt), Virginia Moyer, M.D., M.P.H., of the Baylor College of Medicine in Houston, said that, in general, patients believe cancer is much more common than it is and assume that early detection is synonymous with cure. This is reflected in a 2004 study about enthusiasm for cancer screening in which 87 percent of adults surveyed said they thought routine cancer screening is almost always a good idea and 74 percent believed that finding cancer early saves lives.
"In the face of all this enthusiasm, many people will not appreciate that for some screening tests, there is evidence of no benefit and even potential harm to persons who receive the service," she said.
Inappropriate Cancer Screenings Continue, Study Finds
Active Monitoring of Low-risk Prostate Cancer Gets Closer Look
American Family Physician: AFP by Topic: "Cancer"
(Some content available to members/paid subscribers only)
BMJ: "Simple Tools for Understanding Risks: From Innumeracy to Insight"
(Sept. 25, 2003)