The review, which included data from 24 published studies, further revealed that supplemental diagnostic screenings for women categorized as having dense breasts, while identifying additional breast cancer cases, also increases the rate of false-positive findings—and the implications for long-term outcomes is simply unknown at this point.
“This is an important issue given that 28 million women age 40 to 74 years in the United States have dense breasts,” Dr Miglioretti told Cancer Therapy Advisor. “We critically need more information on the best strategies for screening women with dense breasts.”
Breast density decreases the accuracy of screening mammography and increases breast cancer risk, Dr Miglioretti explained.
“Research is urgently needed to determine whether digital breast tomosynthesis (3D mammography) or supplemental screening with ultrasound or magnetic resonance imagining is more effective than screening with digital mammography alone.”
3D mammography is “quickly diffusing into clinical practice” despite limited information about comparative effectiveness, Dr Miglioretti cautioned.
“Rigorous comparative studies of supplemental screening with long-term follow-up of clinical outcomes are needed before evidence-based recommendations can be made for women with dense breasts,” lead study author Joy Melnikow, MD, MPH, of UC Davis in Sacramento, told Cancer Therapy Advisor.
Dense breast tissue reduces mammography sensitivity, making cancers appear white on a dense white background, and therefore harder to detect, noted Anees Chagpar, MD, FRCS(C), FACS, a breast cancer surgeon and associate professor at the Yale School of Medicine in New Haven, CT.
There is also “some data that breast density may be associated with increased risk” of cancer, Dr Chagpar told Cancer Therapy Advisor.
Currently, 24 states require that radiologists report breast density findings to women undergoing mammography.
“Many states, including Connecticut, have made it legally binding for radiologists to report a woman’s breast density on their mammography, and to inform patients that they should discuss the implications of this and/or recommendations for further imaging with their doctors,” Dr Chagpar noted. “It is clear that supplemental testing, either with ultrasound or magnetic resonance imaging, can lead to finding more cancers in women with dense breasts; but whether these findings actually translate into improvements in survival, is less clear.”
3D tomosynthesis will “make a big difference for women with dense breasts,” Dr Chagpar believes. It allows thin-section imaging, “like layers of onion skin rather than trying to find lesions by looking at the onion as a whole,” she explained.
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Meanwhile, however, “it’s important that women and their physicians not overreact to information about breast density, and consider other breast cancer risk factors in making screening decisions,” Dr Melnikow said.
“As more data emerge, I think we’ll have better recommendations to give our patients,” Dr Chagpar said. “For now, however, it’s good for women who have dense breasts to know their risks, and to talk to their doctors about what imaging is right for them.”
- U.S Preventive Services Task Force. Final recommendation statement: screening for breast cancer. http://www.uspreventiveservicestaskforce.org/Announcements/News/Item/final-recommendation-statement-screening-for-breast-cancer. Accessed January 29, 2016. Updated January 2016. Accessed January 29, 2016.
- Miglioretti DL, Lange J, van den Broek JJ, et al. Radiation-induced breast cancer incidence and mortality from digital mammography screening [published online ahead of print January 12, 2016]. Ann Intern Med. doi: 10.7326/M15-1241.
- Melnikow J, Fenton JJ, Whitlock EP, et al. Supplemental screening for breast cancer in women with dense breasts: a systematic review for the U.S. Preventive Services Task Force [published online ahead of print 12 January 2016]. Ann Intern Med. doi: 10.7326/M15-1789.
- Making a safe procedure even safer [news release]. Sacramento, CA: UC Davis Health System; January 11, 2016. https://www.ucdmc.ucdavis.edu/publish/news/newsroom/10655. Accessed January 29, 2016.