Mammograms No Help Before Age 50
Breast Cancer Experts Tell Women What They Should Do
Robert A. Smith, MD, director of breast cancer screening at the American Cancer Society, is an outspoken critic of the Canadian study.
"Despite the best intentions, some studies have such serious flaws that their findings simply do not reflect the underlying truth," Smith says in a statement. "The goal of screening is to reduce the incidence rate of advanced disease, so that treatment begins earlier. The Canadian investigators failed to accomplish this, so we see no difference in their death rates."
A study recently co-authored by Smith compared the medical records of Swedish women who actually got mammograms with those of women who did not. It found a 45% reduction in breast cancer in the screened women.
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."