Mammography is 'imperfect' test

Until two years ago, medical groups largely agreed women should get annual mammograms beginning at age 40. In 2009, the U.S. Preventive Services Task Force, a group of doctors who evaluate screening tests, broke ranks by encouraging women to talk to their doctors and make up their own minds.

Yet the debate continues. While few dispute the facts about mammograms, they often disagree on how women should act on results, says Otis Brawley, chief medical officer at the American Cancer Society.

For women in their 40s, mammograms reduce the risk of dying from breast cancer by about 15 percent, he says. But mammograms miss some cancers and raise false alarms about others, causing women to go through unnecessary follow-up tests, he says. ''We're saying, 'Mammography is a terribly imperfect test, but we're recommending women get it,''' Brawley says. ''The task force was saying, 'Mammography is a terribly imperfect test, and women have to make a decision about whether to get it in their 40s.' "

Barbara Monsees of the American College of Radiology still believes all women 40 and older need mammograms. That's because 75 percent of women with breast cancer have no known risk factors, she says.

But mammograms offer very different benefits, depending on a woman's age, says surgeon Susan Love, author of "Dr. Susan Love's Breast Book." In young women, breast cancers often grow too fast for mammograms to catch, appearing in between annual screenings, Love says.

Most women sharply overestimate both their risk of breast cancer and the benefits of mammograms, says Lisa Schwartz, a physician and researcher at the VA Outcomes Research Center in White River Junction, Vt. In a population of 10,000 women who are 40 years old, about 35 will die of breast cancer within 10 years. Getting a mammogram helps trim those odds, but only a little, saving five lives per 10,000. ''It's not like we want to deprive young women of their God-given right to be radiated,'' Love says. ''It just doesn't work that well for them.''

Schwartz says mammograms' benefits must be balanced against their risks. In a group of 10,000 women screened with mammograms, up to 2,000 will undergo an unnecessary biopsy, and up to 50 will get unnecessary treatment because a mammogram detects a slow-growing tumor of a type that would never prove life-threatening, she says. ''The cancers that screening is really best at finding are the 'good' ones that are never going to kill you anyway,'' Love says.

An estimated 1 percent to 10 percent of breast cancers are likely non-life-threatening, according to an analysis by oncologist Ellen Warner published in September in the New England Journal of Medicine.

Because doctors can't tell which breast tumors are destined to be life-threatening, they advise removing all of them, Love says. Yet therapies such as surgery, radiation, chemo and long-term hormone pills can mean serious, long-term side effects, says Warner.

Many women feel pressure to get mammograms; it's seen as the ''responsible'' thing to do, Schwartz says. ''Women don't want to (skip screening, then) feel like, 'Now I have this terrible cancer and it's all my fault.' ''

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