Nearly half of women have dense breast tissue, which can be a double whammy on their odds for breast cancer.
Not only are dense breasts a risk factor for cancer, but this glandular and fibrous connective tissue make it harder to detect cancers on a mammogram, the usual method for breast cancer screening.
New research looked at other kinds of imaging to see which might be more effective for the 47% of women who have dense breasts with low levels of fatty tissue.
One emerged as an effective alternative: Breast MRI was superior to other methods, using that detection criteria.
Researchers also looked at hand-held breast ultrasound, automated breast ultrasound and digital breast tomosynthesis.
All showed about the same level of effectiveness, said study co-author Dr. Vivianne Freitas, an assistant professor at the University of Toronto and a staff radiologist at the Joint Department of Medical Imaging, also in Toronto.
"I would say supplementary image modalities in those with dense breasts and negative mammogram are recommended and should be performed," Freitas said. "This is my first message to [patients who have dense breasts]."
Even though the studies found MRI superior in terms of cancer detection, Freitas urged patients to discuss the pros and cons of each method with their health care providers.
Among the concerns about breast MRI is its availability and its price.
"The costs are actually the biggest barrier for our widespread implementation of MRI," Freitas said.
Screening mammograms are highly effective for women with fatty breasts, detecting about 98% of cancers. For those with dense breasts, they can give false reassurance, however.
Both dense tissue and breast cancer show up as white on the image, making it harder to detect cancer in dense breasts, Freitas said.
On average, women have a lifetime risk of 12% to 13% for developing breast cancer. A history of treated breast cancer or previous breast biopsies with high-risk lesions boosts that to an intermediate risk.
High-risk patients, with a lifetime risk of 20% or higher, were not included in this study because MRI benefits for them have already been established.
To investigate the effectiveness of screening methods, the researchers did a meta-analysis of 22 studies that included more than 261,000 patients who had been screened for breast cancer.
The studies included 10 that covered hand-held breast ultrasound; four on automated breast ultrasound; three on breast MRI; and eight on digital breast tomosynthesis.
More than 132,000 of the women had dense breasts and a negative mammogram. Researchers found 541 undetected cancers in that group. Breast MRI detected even tiny cancers.
Still, more research is needed, researchers said. It's important to investigate the cost effectiveness of breast MRI and any impact each method may have on death rates.
Susan Brown, a managing director at the Susan G. Komen breast cancer organization in Dallas, reviewed the findings.
She noted that MRI technology is much more sensitive but also not very specific, which can lead to false positives.
Brown said she would like to see the additional research that the authors also said was needed on the impact of other screening methods on cancer survival.
“We don't know if using breast MRI as a supplemental screening to mammography for women at average risk with dense breasts really saves lives,” she said.
In the absence of clinical guidelines, Brown said decisions on follow-up screening is a personal judgment call.
Komen's policy focus has been on removing barriers to breast imaging, she said.
Although the Affordable Care Act enabled widespread access to free screening mammograms, patients who need additional screening because of an inconclusive or abnormal mammogram may still incur high out-of-pocket costs.
“Our position is that mammography is one step, the initial step, in early detection and is alone not able to diagnose breast cancer in every woman, and women with breast density is an example,” Brown said.
People who face high costs for diagnostic and supplemental imaging are less likely to have those tests, she said, citing past research.
“As a result, if they have breast cancer, that delay in diagnosis can be associated with a much poorer outcome,” Brown said.
Nine U.S. states have eliminated cost sharing for these follow-up tests, Brown said. Several others have introduced legislation this year to address this issue. Federal legislation may also be reintroduced later this year.
“To have that screening test but then not to be able to follow up if there's an abnormality can have really very negative consequences, of course, to those individuals that do have cancer,” Brown said.
The findings were published Jan. 31 in the journal Radiology.
The U.S. National Cancer Institute has more about dense breasts.
SOURCES: Vivianne Freitas, MD, MSc, assistant professor, University of Toronto, and staff radiologist, Joint Department of Medical Imaging, Toronto, Canada; Susan Brown, MS, RN, managing director, Health and Mission Program Education, Susan G. Komen, Dallas; Radiology, Jan. 31, 2023