Women at high risk for developing invasive breast cancer now have a more definitive answer for appropriate screening methods, given an American College of Radiology Imaging Network trial reported April 4 in the Journal of American Medical Association.
The study confirms a significant breast cancer detection benefit by supplementing annual mammography screening with ultrasound in women at elevated risk due to dense breast tissue and at least one additional risk factor such as family history of the disease. The study also found that a single screening MRI following three years of annual mammography and ultrasound screenings identified additional cancers. The majority of additional cancers detected by the supplemental ultrasound and MRI screenings were early-stage invasive cancers that had not spread to the lymph nodes.
"For women who have dense breasts, adding ultrasound to mammography will increase the chance of finding invasive cancer before it spreads to lymph nodes," said the trial's principal investigator Wendie Berg, M.D., Ph.D., professor of radiology at the University of Pittsburgh School of Medicine, Magee-Womens Hospital of UPMC. "MRI detected additional invasive cancers not seen on mammography or ultrasound; however, we found that MRI was significantly less tolerable than mammography or ultrasound for many study participants. Of participants offered an MRI, only 58 percent accepted the invitation."
Berg also noted that the study results confirm that mammography alone is not the best screening process for women with dense breasts. MUSC College of Medicine Dean Etta Pisano, M.D., served as a co-author and investigator of the study, and agreed with Berg that study results illuminated a much better picture of what ultrasound screening can do to protect high-risk women, and that a costly MRI is not always the answer.
"It is important for each patient to speak with her physician about which screening process is most appropriate given her own medical history," said Pisano. "Women with dense breast tissue should not assume that having an ultrasound or MRI is essential."
Study results were reported for 2,662 women at increased breast cancer risk who had three annual mammography plus ultrasound screenings and for a subset of 612 study participants who agreed to undergo an MRI after completing all three mammography and supplemental ultrasound screenings. A total of 111 breast cancer diagnoses were made in 110 study participants with 33 (30 percent) cancers seen only by mammography and 32 (29 percent) cancers seen only by the supplemental ultrasound, for an added annual cancer detection rate due to ultrasound of 4.3 cancers per 1,000 screens. The single MRI screening revealed additional cancers not seen by mammography or ultrasound at a rate of 14.7 per 1,000 screens. Nine cancers ("interval" cancers, 8 percent) were detected clinically in between the annual imaging exams (1.2 per 1,000 screens).
Of the 32 cancers seen only on ultrasound, 30 (94 percent) were invasive, accounting for a 34 percent absolute increase in invasive cancer detection, and of the nine cancers seen only on MRI, eight (89 percent) were invasive.
Ellen Mendelson, M.D., co-investigator and Lee F. Rogers Professor of Radiology at the Feinberg School of Medicine, Northwestern University, Chicago gave these guidelines. "While supplemental ultrasound and MRI screening detect more cancers, it is important to emphasize that an annual mammogram is still recommended and neither ultrasound nor MRI is meant to replace mammography," she said.
The authors also reported the risk of false positives decreased significantly with annual screening ultrasound in this study compared with the first screen.
The study was made possible through funding from a novel private-public partnership between the Avon Foundation and the National Cancer Institute, part of the National Institutes of Health.