Breast Density Takes Center Stage

By Melinda Taschetta-Millane

Slowly, the push from advocates is starting to gather legislative momentum as more and more women become aware of breast density and the devastating effects it can have on their own health, and as more states pass breast density notification laws. Today at RSNA, two related studies were discussed.

A major new study has found that 3-D mammography has the potential to significantly increase the cancer detection rate in mammography screening of women with dense breasts. Other imaging modalities such as ultrasound and MRI are often used to help find cancers that can't be seen on mammograms, but both modalities have higher rates of false-positive findings. Per Skaane, M.D., Ph.D., Department of Radiology at Oslo University Hospital in Oslo, Norway, and his colleagues have been studying tomosynthesis as a promising breast cancer screening option that addresses some mammography’s limitations.

"Tomosynthesis could be regarded as an improvement of mammography and would be much easier than MRI or ultrasound to implement in organized screening programs," Skaane said. "So the intention of our study was to see if tomosynthesis really would significantly increase the cancer detection rate in a population-based mammography screening program."

The researchers compared cancer detection using full-field digital mammography (FFDM) versus FFDM plus digital breast tomosynthesis in 25,547 women between the ages of 50 and 69. Breast density was classified based on the American College of Radiology's Breast Imaging-Reporting and Data System (BI-RADS). FFDM plus tomosynthesis pinpointed 80 percent of the 132 cancer cases in women with dense breasts, compared to only 59 percent for FFDM alone. "Our findings are extremely promising, showing an overall relative increase in the cancer detection rate of about 30 percent," Skaane said. "Stratifying the results on invasive cancers only, the relative increase in cancer detection was about 40 percent."

Another study of breast cancers detected with screening mammography found that strong family history and dense breast tissue were commonly absent in women between the ages of 40 and 49 diagnosed with breast cancer. "Screening recommendations for this age group continue to be debated," said Bonnie N. Joe, M.D., Ph.D., associate professor in residence and chief of women's imaging at University of California, San Francisco (UCSF). "Recent publications have suggested risk-based screening based on family history and breast density. However, our study shows that this approach would miss a significant percentage of invasive cancers and could potentially be dangerous."

The study found that almost 90 percent of the invasive cancers would have been missed using risk-based triage. Of the 136 breast cancer cases identified, 50 percent were diagnosed as invasive, and 50 percent were diagnosed as ductal carcinoma in situ (DCIS), although 88 percent of DCIS cases were intermediate or high grade.

"Our results show that by exclusively using a risk-based approach to screening mammography, we could potentially miss more than 75 percent of breast cancers in women in their 40s, thereby eliminating most of the survival benefit from screening mammography that has been previously shown in randomized controlled trials," Joe said. She urges proponents of risk-based screening to continue research to find more effective means of risk-based triage.

"Based on our current knowledge and evidence shown in previous trials, it is still safest to get annual mammograms starting at age 40 in order to maximize the survival benefit of screening mammography," Joe stressed.

And so the debate will continue, however progress is indeed being made.

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