Ask Dr. Marie: Mammograms Not Always a Good Idea

Two recent studies remind me that frequent and early screening mammograms may not always (emphasis on "not always") be a good idea.

The first study in the Journal of the American Medical Association looked at women who received chest radiation as a child and found that only about half of the women had a screening mammogram within the previous two years, despite evidence that their exposure to radiation as children may increase their risk of breast cancer.

The article's headline seemed to suggest that women with such a risky history were in some way negligent when, in fact, they (or their doctors) may have been appropriately cautious about doing too many X-rays. An accompanying editorial wisely suggested that maybe women with childhood radiation should have less exposure to X-rays rather than more exposure. The editorial raised the question about whether perhaps breast MRIs would be a better way to screen high-risk women with a history of childhood radiation to avoid unnecessary and potentially risky X-ray exposure.

The second study questioned whether the current recommendations for women who have inherited one of the two known breast cancer genes, BRCA 1 or BRCA 2, to begin screening mammograms at age 25 or 30 makes good sense.

Researchers looked at a mathematical model calculating radiation exposure in young women receiving regular mammograms and compared this potential risk to increase breast cancer from X-rays to the potential benefit of starting mammograms at a young age. Their model suggested the increased risk of breast cancer from exposure to the radiation by doing the X-rays may outweigh any benefit of screening for young women at high risk for cancer because they have inherited one of the breast cancer genes, BRCA 1 or 2.

Blast From the Past: Mammogram Concerns

These studies take me back to the early 1980s when the controversy around the benefits versus the risks of mammograms took center stage in the screening debate.

The argument against mammograms back then was as follows: Because mammograms require exposure to ionizing radiation, a known risk factor for breast cancer, why would you expose a woman's breast to this radiation year after year with only marginal hope that a cancer will be detected early enough to improve outcome?

More Radiation, More Risk

Some scientists believed at the time that the risk of cancer related to radiation exposure was linear, meaning that the more radiation you were exposed to, the greater the risk. They also thought that the younger the breast tissue was when exposed to radiation, the greater the chance of damaging the breast. In fact, for this reason, most experts rarely recommend a woman younger than 35 years of age receive a screening mammogram. Of course, back then mammograms delivered much more radiation and the pictures were much less clear than mammograms done today.

Other scientists at that time believed that the small amount of radiation was not enough to pose a breast cancer risk. Yet studies from survivors of the atomic bomb and women with tuberculosis (in the days before antibiotics) who were exposed to frequent, often daily, chest X-rays for monitoring their disease did show that higher doses of radiation increased the risk of breast cancer.

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