Pro-Mammogram Statistics Draw Challenge

Pro-Mammogram Statistics Draw Challenge

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An awareness campaign on breast cancer by research group Susan G. Komen for the cure has overstated the benefits of mammograms for the survival rates of women with breast cancer, researchers say in a new editorial.

Komen’s messages in his 2011 campaign said that 98 percent of women who receive screening tests survive for at least five years, while 23 percent of women who do not receive mammograms survive that long – a difference of 75 percentage points.

However, in an online editorial in the British Medical Journal, two researchers argue that randomised controlled trials have shown that mammograms reduce the risk of dying from the disease many times over. For example, in people with breast cancer at the age of 60, the risk of dying from the disease over a period of 10 years dropped from 83 percent to 56 percent – a difference of 27 percentage points.

“The advertising campaign does not present screening as a real choice – it suggests that you have to be crazy or stupid not to be screened,” said editorial writer Dr Steven Woloshin, professor at Dartmouth College’s Hostage School of Medicine. Whether or not to get screened is actually a “real decision, because there are advantages and disadvantages,” Woloshin said.

A Komen spokesman defended the campaign statements. “The numbers are not in question. Early detection allows for early treatment that gives women the best chance of survival for breast cancer,” said Chandini Portteus, Komen’s vice-president.

The reasons for screening

Voloshin asked whether a personal decision should be reviewed, based on factors such as age and family history. For example, younger women generally have less breast cancer, but those with a strong family history of the disease may want to be examined earlier.

Screening has been associated with a decrease in mortality from breast cancer, but the decrease is not as dramatic as Komen suggested, said Harvard Medical School radiologist Dr Daniel Kopans.

Randomised control trials have generally shown that screening reduces the number of lives lost to breast cancer by about 30 percent, Kopans said. In the US, deaths due to breast cancer have also decreased by about 30 percent since screening was introduced in the 1980s.

“Thirty percent fewer women die of breast cancer each year than without screening,” Kopans said, noting that part of this benefit is due to improvements in the treatment of earlier stages of the disease. “Therapy saves lives if cancer is found early,” he said.

However, critics of mammograms say they can trigger false positives that lead to unnecessary biopsies. Portteu’s response: “Everyone agrees that mammography is not perfect, but it is the best detection tool generally available today”.

A misleading advertisement

Komen’s campaign was promoted last October and designed and funded by the Komen Foundation, which has raised over $1.9 billion for breast cancer awareness, research and support for patients.

Voloshin and his co-author Lisa M. Schwartz of Dartmouth argue that the survival statistics used to support the Komen message about screening were misleading. This is a “disingenuous presentation of statistics,” Woloshin said, as screening adds a “lead time” between finding cancer and being dangerous.

For example, according to the authors, we look at a group of women who are not examined but find a breast lump at age 67 and are then diagnosed. When these women all die at the age of 70, their five-year survival rate is 0 percent. Now imagine another group of women who were examined and diagnosed with breast cancer at 64 years of age. If these women also all die at 70, then their 5-year survival rate is 100 percent – even though both groups lived to the same age.

Organisations that promote cancer screening “have cut out their work for them,” Kopans said. “They are trying to convince women to do a test that nobody wants to do.” In this case, Komen exaggerated, he said.

The problem of overdiagnosis

The problem of screening is further controversially discussed by the problem of overdiagnosis: Some women are treated with chemotherapy or surgery, although their cancers would never become dangerous or affect their lives, Voloshin said.

Randomised control studies have shown that overdiagnosis occurs in 1 to 10 percent of screening cases, Kopans said. But he said that this risk is worth the number of lives that screening ultimately saves.

Women should base their decisions on whether to be screened by weighing the facts and consulting with their doctors, Woloshin said. The Komen website provides detailed information on the advantages and disadvantages of screening, he said.

Woloshin hopes that Komen will reconsider the use of statistics when they run a similar advertising campaign this October.

The paper was published today (August 2) in the British Medical Journal.

Pass it on: Mammograms reduce mortality

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