Mammograms No Help Before Age 50
Breast Cancer Experts Tell Women What They Should Do
The leader of the Canadian study, Anthony B. Miller, MD, dismisses these findings.
"That Swedish population study was terrible," Miller tells WebMD. "It has all the biases of historical comparisons. It was not randomized, they over-interpreted their data, they cannot from their data determine how much of the reduction in cancer deaths was due to better treatments and how much was due to mammography. Yet, they say the benefit was largely due to mammography."
An editorial by Steven Goodman, MD, PhD, MHS, of Johns Hopkins Sidney Kimmel Cancer Center, Baltimore, accompanies the Canadian and USPSTF studies.
"It is wrong to look at the Canadian study as a line in the sand," Goodman tells WebMD. "It does not say there is no effect from mammography in women aged 40-49. It says there is a range of possible effects, and this is closer to zero than other studies. All the clinical studies of mammography are similar -- they overlap in the region of very modest benefit."
Whatever the benefit of mammograms in 40-something women, Goodman warns that it must be weighed against the risks. The main risk is a false-positive finding -- that is, a mammogram that says a biopsy is needed when there turns out to be nothing wrong. Such findings lead to biopsies, lumpectomies, and even mastectomies. They also cause a great deal of anxiety.
"The chance of a false-positive mammogram and subsequent biopsy is 40-50% if you have 10 mammograms," Goodman says. "And the benefit is extremely small if it exists at all. For a woman in her 40s, the risk of dying from breast cancer is only 1 in 350-400. The benefit is on the order of 1 in 2000 -- one of the smallest benefits known to medicine."
What Should Women Do?
WebMD asked each of the breast-cancer experts cited above what they would tell a woman in her 40s to do about breast-cancer screening. Their replies:
Humphrey: "I practice medicine. My own belief is that mammography probably is effective and better than nothing -- but it has risks. It is really important to discuss the risks with women. I tend to recommend it in my practice: mammograms every one to two years. I recommend more frequent mammograms in younger women than in older women, as cancers may be faster growing in younger women."
Goodman: "I do not have a clinical practice, so it's far too easy for me to say what to do from my ivory tower. But my wife and our friends are exactly in that age group. Most of them, not all, are choosing not to have mammograms because they understand that negative consequences are quite probable. It is such a close call with real issues on both sides of the scale. I would never, ever say to someone, 'You should do or not do this.' I would say, 'These are the positives, these are the negatives, you decide. There are real harms and real benefits that come very close to even."