JNCI: Mammo for younger women has low accuracy, detects few cancers

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While screening mammograms for women under 40 result in a high rate of callbacks and further imaging tests, they also result in low rates of cancer detection, according to a study published online May 3 in the Journal of the National Cancer Institute.

Bonnie Yankaskas, PhD, from the department of radiology at the University of North Carolina in Chapel Hill, and colleagues pooled data from six mammography registries across the U.S. from the Breast Cancer Consortium. The study included 117,738 women between the ages of 18 and 39 when they had their first screening or diagnostic mammogram during the years 1995-2005 and followed the women for a year to determine the accuracy of the tests and cancer detection rates.

The researchers found that no cancers were detected in the 637 mammograms for women under the age of 25. Women aged 35-39 years had the largest number of screening mammograms in this study (73,335) and the recall rate was 12.7 percent, sensitivity was 76.1 percent, specificity was 87.5 percent, positive predictive value was 1.3 percent and the cancer detection rate was 1.6 cancers per 1,000 mammograms.

For diagnostic mammograms, the cancer detection rate was 14.3 cancers per 1,000 women aged 35-39.

The authors concluded that while younger women have very low breast cancer rates they do experience high callback rates and high rates of additional imaging after mammography screening. They also found that in a theoretical population of 10,000 women having a screening mammogram between ages 35 and 39, 1,266 would be called back for further testing, 16 cancers would be detected, and therefore 1,250 women would have false positives.

“Our findings support a need for serious discussion about the appropriateness of mammography in women without the presence of symptoms,” the authors wrote.

In the accompanying editorial, Ned Calonge, MD, of the Colorado Department of Public Health and Environment, wrote that this "landmark descriptive study should inform women and physicians and guide research efforts" on early detection in younger women. He pointed out that the women in the study with a family history of breast cancer had the same detection and false positive rates as those women without a known family history, calling into question the idea that women with known family histories of breast cancer should undergo screening earlier.

"The study...is a powerful reminder that we must continue to strive for better tests and better treatments,” he wrote. “Furthermore, we should not be satisfied with better detection rates alone. We need evidence that early detection of these cancers translates to improvements in important health outcomes."