Computer-Aided Detection Mammograms Finds Cancers Earlier but Increases Risk of False Positives

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A large study suggests that using computers to help read older women’s mammograms – called computer-aided detection (CAD) – means more invasive breast cancers are found earlier and more DCIS (ductal carcinoma in situ) is found. But using CAD also increased the risk of a false-positive result.

A mammogram can identify an abnormal area that looks like cancer but turns out to be normal. This “false alarm” is called a false positive. Besides the stress and worry of a possible cancer diagnosis, a false positive usually also means more doctor visits and tests, including possibly a biopsy.

DCIS is not invasive cancer; it’s called stage 0 breast cancer. DCIS stays inside the breast milk duct and doesn’t spread outside the milk duct into the surrounding normal breast tissue, lymph nodes, or other organs.

The research was published in the April 16, 2013 issue of the Annals of Internal Medicine. Read the abstract of “Short-Term Outcomes of Screening Mammography Using Computer-Aided Detection: A Population-Based Study of Medicare Enrollees.”

With CAD, a computer program highlights areas on the mammogram image that MAY be abnormal. A radiologist has to decide if the areas really are abnormal. CAD isn’t the same as having a second radiologist look at the mammogram. With CAD, only one radiologist looks at the mammogram.

In this study, the researchers wanted to know how CAD mammograms affected the results of routine breast screening in older women. So they looked at Medicare information from more than 163,000 women who had either CAD mammograms or mammograms without CAD. The information was linked to a National Cancer Institute database of cancer diagnoses, treatments, and survival. The women were 67 to 89 years old when they had mammograms from 2001 to 2006. The researchers noted that CAD mammograms increased from 3.6% in 2001 to 60.5% in 2006.

Compared to women who had mammograms without CAD, women who had CAD mammograms had a:

  • 17% increase in DCIS diagnoses
  • 6% increase in early-stage invasive cancer diagnoses

In women diagnosed with invasive cancer, CAD mammograms tended to find the cancer at stage I or stage II compared to stage III or stage IV.

Women who had CAD mammograms and weren’t diagnosed with breast cancer had more false positives that led to a:

  • 19% increase in additional tests
  • 10% increase in breast biopsies

compared to women who had mammograms without CAD and weren’t diagnosed with breast cancer.

The rate of invasive cancer diagnoses was similar between women who were screened with CAD mammograms and women who had mammograms without CAD. Still, the invasive cancers were more likely to be found at an earlier stage in women who had CAD mammograms. Breast cancer is more treatable when it’s found at an early stage.

This study didn’t look at whether women who had breast cancer found at an earlier stage by CAD mammograms had better survival than women who had breast cancer found at a later stage by a mammogram without CAD.

Some doctors question the benefits of CAD because they think that if radiologists come to rely on CAD to read mammograms, these radiologists may be less careful when reviewing mammograms, which would mean less accurate readings. Other doctors wonder if CAD mammogram screening is increasing costs without adding any benefits and possibly doing more harm than good because of the higher likelihood of false positives.

More research is needed to figure out the best ways to use CAD, as well as study whether CAD mammograms improve survival in women who are diagnosed with breast cancer.

Mammograms aren’t perfect, but they’re the best way to find breast cancer early, when it’s most treatable. As you and your doctor develop your breast cancer screening plan, you may want to ask these questions:

  • Are any of the mammography centers near me better than the others?
  • Is digital mammography available? (Research has shown that digital mammography can be more accurate than film-based mammography.)
  • Will the radiologist read my mammogram using CAD?
  • Is my most recent mammogram being compared to my older mammograms when it’s being read? (Comparing the new to the old has been shown to improve reading accuracy.)
  • Does a second radiologist routinely review any suspicious mammograms before a final interpretation is made? (Second readings improve mammogram accuracy.)

In the Breastcancer.org Screening and Testing section, you can learn more about mammograms and other ways to screen for breast cancer.

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