Just because a new study shows that mammography may not save lives, don’t expect the organizations that set breast cancer screening guidelines to automatically adjust their recommendations on who should get mammograms and how often.
A Canadian study published this week in the British Medical Journal tracked some 90,000 women over 25 years and found that women who underwent annual mammograms were no less likely to die from breast cancer than those who simply examined their own breasts for signs of disease. In light of this finding—along with the fact that the study included a large sample size tracked over a long period of time—it might seem logical that groups like the American Cancer Society (ACS) will alter their recommendation that all women over 40 get mammograms every year. Not so fast.
Otis Brawley, chief medical officer for the ACS, has been outspoken about the downside of various types of cancer screening, arguing that benefits are often over-stated. But even he points out that the ACS examined the ongoing Canadian study when the group last updated its breast cancer screening guidelines seven years ago and concluded that annual mammograms for women over 40 were still warranted. (Findings from the study back then were similar to those published this week.) The ACS will take a fresh look at the research on mammography this year and may change its recommendations, but there’s no guarantee.
The U.S. Preventive Services Task Force, a government panel that exhaustively analyzes research and writes its own breast cancer screening guidelines, has concluded that annual mammograms for women in their forties reduces the relative risk of death by 15%. This means that for every 1,900 women who undergo annual mammograms, one life will be saved due to early detection. The downside of such population-based screening, which the Canadian researchers pointed out in their study, is that some women will undergo surgery, radiation and other treatments unnecessarily when non-fatal cancers or masses that look like cancer but are not are detected. Weighing this, the government panel revised their recommendations in 2009 to mammogram screenings every two years beginning at age 50.
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But even beyond the tricky business of weighing benefits against harms, Brawley says there are aspects of the Canadian mammogram study that may undercut its findings. Although the trial used randomization, the gold standard in clinical research, women were assigned to receive or skip mammograms after they underwent breast exams. “That’s not a clean randomization,” says Brawley, “There might be some biases.”
Still, Brawley says be believed mammography has merit. “I understand peoples’ frustration,” he says, “but the truth is that medical science is not an exact science. It’s called research because you’re continuing going back to search and find the truth.”
Just as important than screening, Brawley adds, are advances in treatment, which can sometimes get lost in the public push to encourage women to get mammograms. “The talk about screening versus no screening takes away from the fact that there are thousands of women who get no treatment after they get screened and diagnosed.”
Critical improvements in treatment for breast cancer, like better chemotherapy and drugs, have saved countless lives and reduced the benefits of screening over time because cancers detected later (and without the use of mammography) are now more treatable than before. “The ultimate goal is that screening is not needed because treatment is so good,” says Brawley. “But I don’t plan on seeing that in my lifetime.”