Pro-Mammogram Statistics Draw Challenge
A breast cancer awareness campaign by the research advocacy group Susan G. Komen for the Cure overstated the benefit that mammograms have on survival rates of women with breast cancer, researchers say in a new editorial.
Komen's messages in its 2011 campaign stated that 98 percent of women who get the screening tests survive at least five years, while 23 percent of women who do not get mammograms survive that long — a difference of 75 percentage points.
In an online editorial in the British Medical Journal, however, two researchers argue that randomized controlled trials have shown mammograms reduce the risk of dying from the disease by far less. For example, among those with breast cancer who are in their 60s, the risk of dying over a 10-year period is reduced from 83 percent to 56 percent — a difference of 27 percentage points.
"The ad campaign doesn’t present screening as a genuine choice — it suggests you'd have to be crazy or stupid not to get screened," said editorial author Dr. Steven Woloshin, a professor at Dartmouth College's Geisel School of Medicine. Whether or not to get screened is actually a "genuine decision, because there are benefits and harms," Woloshin said.
A Komen spokesman defended the campaign statements. “The numbers are not in question. Early detection allows for early treatment, which gives women the best chance of surviving breast cancer,” Komen vice president Chandini Portteus said.
The reasons for screening
Woloshin called whether to get screened a personal decision that should be based on factors including age and family history. For example, younger women are less likely to have breast cancer in general, but those with a strong family history of the disease might want to be screened earlier.
Screening has been associated with a decrease in mortality due to breast cancer, but the decrease is not as dramatic as Komen suggested, said Harvard Medical School radiologist Dr. Daniel Kopans.
Randomized control trials have found, in general, that screening reduces the number of lives lost to breast cancer by approximately 30 percent, said Kopans. In the U.S., deaths due to breast cancer also have decreased by about 30 percent since screening was instated in the 1980s.
"Thirty percent fewer women die each year from breast cancer than would have without screening," Kopans said, noting that part of this benefit is due to improvements in treatments for earlier stages of the disease. "Therapy saves lives when you find cancer early," he said.
Still, critics of mammograms say they can produce false alarms that lead to unnecessary biopsies.Portteus' reply: "Everyone agrees that mammography isn’t perfect, but it’s the best widely available detection tool that we have today."
A misleading advertisement
Komen's campaign was promoted last October and was designed and funded by the Komen foundation, which has raised over $1.9 billion for breast cancer awareness, research and support to patients.
Woloshin and his co-author, Lisa M Schwartz of Dartmouth, argue that the survival statistics used to support the Koman message about screening were misleading. This was a "disingenuous representation of statistics," Woloshin said, because screening adds a "lead time" between when cancer is found and when it becomes dangerous.
For instance, the authors wrote, consider a group of women who aren't screened but find a breast lump at age 67, and are subsequently diagnosed. If these women all die at age 70, their five-year survival rate is 0 percent. Now imagine another group of women, who were screened and diagnosed with breast cancer at age 64. If these women also all die at age 70, their five-year survival rate is 100 percent — even though both groups lived to the same age.
Organizations pushing cancer screening "have their work cut out for them," Kopans said. "They're trying to convince women to take a test that nobody wants to take." In this case Komen exaggerated, he said.
The problem of overdiagnosis
The issue of screening is further made controversial by the problem of overdiagnosis: Some women are treated with chemotherapy or surgery even though their cancers would never become dangerous or affect their lives, Woloshin said.
Randomized control trials have found that overdiagnosis occurs in 1 percent to 10 percent of screening cases, Kopans said. He said, however, this risk is worth the number of lives that are ultimately saved by screening.
Women should base their decisions on whether to be screened by weighing the facts and consulting with their doctors, Woloshin said. The Komen website does provide accurate information on the benefits and harms of screening, he said.
Woloshin said he hopes Komen reconsiders their use of statistics if they run a similar ad campaign this October.
The paper was published today (August 2) in the British Medical Journal.
Pass it on: Getting mammograms decreases mortality.
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