Routine Mammograms Before 50: Not Much Point

On balance, they do more harm than good, a government task force concludes in new recommendations.

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The government's independent panel of preventive health experts has now recommended that women in their 40s not automatically be screened for breast cancer using mammography. But will—and should—women listen? Today's announcement by the U.S. Preventive Services Task Force, historically conservative in its recommendations, puts it at odds with plenty of other organizations, including the American Cancer Society, the American College of Obstetricians and Gynecologists, and breast cancer advocacy and information groups such as Susan G. Komen for the Cure and

The notion of screening 40-something women at normal risk of developing the disease has long been controversial, or at least complicated. The American College of Physicians, for example, in 2007 changed its own policy and warned that mammograms in younger women at low risk of breast cancer may do more harm than good. For example, it can expose them to needless follow-up testing, the organization said.

[Slide Show: 11 Screening Tests You Should (or Shouldn't) Consider]

For many women, the USPSTF's updated recommendations are likely to be confusing. The new guidelines also say that women between the ages of 50 and 74 should receive mammograms every two years rather than annually. And the USPSTF says that there's not enough evidence to weigh the benefits and harms of mammograms in women 75 and older or to evaluate newer digital mammography or magnetic resonance imaging as screening techniques for breast cancer. Also, the task force recommends against instructing women how to do self-exams.

Everyone knows a woman whose breast cancer was caught early during her annual mammogram. What could possibly be troublesome about finding tumors before they've had a chance to leave the breast and invade elsewhere in the body?

The USPSTF, whose new screening advice was published in the Annals of Internal Medicine, agrees that mammography saves lives. Referring to a new review of the available evidence, it notes that the screening test cuts the death rate from breast cancer by about 15 percent for women in their 40s—similar to the effects for women in their 50s. (The benefit is significantly larger for women in their 60s.)

But the panel says that there are harms inherent in screening, including false-positive results that cause anxiety and lead to additional tests and invasive procedures such as biopsies. There's also the less-quantifiable risk of finding—and treating—very early invasive cancer or the "stage zero" cancer known as ductal carcinoma in situ (DCIS) that doesn't always progress to become life-threatening. "You can't just focus on the benefits," says Karla Kerlikowske, director of the women's clinic at the Veterans Affairs Medical Center in San Francisco, who wrote an editorial accompanying the USPSTF report. "You have to also think about all the healthy people who are undergoing these tests."

[Read: The Confusion Over DCIS: What to Do About 'Stage Zero' Breast Cancer.]

And cancer is more rare in younger women. The research cited by the USPSTF says that to avert one death from breast cancer, about 1,900 women in their 40s would need to be screened for a decade, compared to 1,300 women in their 50s and 400 in their 60s. After analyzing all this data, the USPSTF says that the net benefits after accounting for harms are small for women younger than 50. Women in their 40s, the task force says, should make personal decisions based on their feelings about the balance of benefits and harms. And women between 50 and 74, the task force says, should get mammograms only every other year, since models show that schedule should produce almost all the benefits with almost half the number of false-positive results.

Some take issue with the new guidelines. With these recommendations, the task force has made "a value judgment that's subject to discussion and interpretation," says Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, which is sticking to its recommendation that women begin annual screening mammograms at age 40. Harms are tricky to measure. It's hard to quantify the psychological impact of additional tests and biopsies, for example. And estimates of overdiagnosis generally range only between 1 percent and 10 percent, according to the review consulted by the USPSTF. (Monetary costs weren't considered by the task force, says USPSTF Vice Chair Diana Petitti.) Lichtenfeld is also concerned about using computer models as the basis for the every-other-year recommendations, since so much is at stake.