Although newer mammography technology may be able to detect more breast cancers, it also is creating more false alarms, two recent studies show.

The studies found that breast X-rays stored as digital files rather than on film were better at finding evidence of cancer, but they also increased the number of "abnormal" results that actually weren't cause for concern.

These false positives create unnecessary surgery—and anxiety—for thousands of women, says Diana Miglioretti, Ph.D., professor of biostatistics at the University of California, Davis School of Medicine and one of the study’s authors.

In the two studies, published in the journal Radiology, researchers with the Breast Cancer Surveillance Consortium reviewed hundreds of thousands of mammograms performed since 2007, about the time when digital mammography technology became the norm, replacing earlier film-based breast cancer tests.

The researchers found an increasing rate of false positives, meaning that more women receiving digital mammograms were having biopsies (when tissues or cells are removed from the breast for testing) that turned out to be benign.

Biopsies can be painful, expensive, and carry a slight risk of infection. And “that waiting period of thinking you have cancer can be quite stressful,” Miglioretti says.

Still, says Robert Smith, Ph.D., vice president of cancer screening for the American Cancer Society, the benefits of digital mammography—more cancers being detected, and when they’re a smaller size—may outweigh the risks of a false alarm for many women.

Making Smart Choices About Breast Cancer Tests

Experts in the field agree that regular breast cancer screening saves lives. Yet it’s also true that the more mammograms a woman receives, the more likely she is to have a false positive.

Several major scientific groups make recommendations to help women navigate the decision of when to start receiving regular breast cancer tests and how often to have them. Though the advice differs, all agree that by age 50 women should be receiving regular mammograms—at least every other year.

Consumer Reports’ medical experts advise that the more risk factors you have for breast cancer—obesity, smoking, a family history of the disease, for example—the more reasonable it is to start receiving mammograms in your 40s. And if you do choose to start screening in your 40s, annual tests make sense, changing to every other year when you reach about age 50. If you start screening in your 50s, you may be better off testing every other year.

If you receive an abnormal test result on a mammogram, Miglioretti says, remember that it doesn’t mean you definitely have cancer.

Over the course of many routine mammograms, “the vast majority of women are going to have at least one false positive,” Miglioretti says. That’s outside of the patient’s control—and often the doctor’s—but consumers should keep in mind that a diagnosis is not usually confirmed until after a biopsy is performed.

There are a couple of ways women may be able to reduce their risk of a false positive, Smith says. First, he suggests, “find a [screening facility] you like and stay with it.” That way, your doctor will be familiar with your history and have access to your past test results for comparison. And if you have to change facilities, he says, ask for a copy of all your old mammograms to give to your new doctor.

If you do receive a cancer diagnosis after being biopsied, says Laura Esserman, M.D., director of the Carol Franc Buck Breast Care Center at the University of California, San Francisco, it’s important to remember that you have time to weigh your treatment options. Immediate aggressive treatment, she says, may not always be the best path.

Ask your doctor:

  • What kind of cancer is this, and how risky is it?
  • What are my treatment options, and what do you recommend?
  • Are there other, simpler options?
  • What happens if I don’t do anything?

If your cancer is low-risk—very slow-growing, for example—Esserman says you may want to consider a wait-and-see strategy: monitoring a tumor to see whether it progresses, rather than treating it immediately.

“There’s a real cultural bias that more [treatment] is better. But more is just more," Esserman says. "Sometimes more is worse.”

And don’t be afraid to ask for a second opinion about the treatment your doctor recommends.