December 10, 2020 | Researchers have been experimenting with abbreviated (aka “fast”) breast MRI for about a decade now and the consensus seems to be that it’s a cost-effective modality for screening women at intermediate risk, including those with dense breast tissue as the sole risk factor. Unlike a typical breast MRI examination that generates several hundred images for interpretation and requires up to 40 minutes for image acquisition, a fast MRI protocol may involve a single pre-and post-contrast image and their derived images, explains Susan Weinstein, M.D., an associate professor of radiology at the University of Pennsylvania School of Medicine.
Fast MRI not only takes a fraction of the time (five to seven minutes) but is also a great alternative to screening breast ultrasound as a supplemental exam for women with dense breasts, which limits the sensitivity of mammography, Weinstein says. The problem is that there’s no reimbursement code for the shortened version, so only a handful of health systems nationwide offer it. Even at Penn Medicine, where abbreviated MRI is an option that patients can pay for out of pocket, demand for the test remains low.
That could soon change, driven in part by findings of a prospective, multi-institutional study published last February in JAMA (DOI: 10.1001/jama.2020.0572) that was co-led by Mitchell D. Schnall, M.D., Ph.D., chair of radiology at Penn Medicine. Abbreviated breast MRI was associated with a significantly higher rate of invasive cancer detection than digital breast tomosynthesis (aka 3-D mammography) among women with dense breasts.
In the same study population, 3-D mammography detected 4.8 invasive cancers per 1,000 while fast MRI detected 11.8 cancers—a whopping 240% more, notes Weinstein. “That’s why I think this is going to be big.”
3-D mammography, approved by the U.S. Food and Drug Administration in 2011, detects about 25% more cancers than standard 2-D mammography, she says. That translates into one additional cancer per 1,000 women.
In a retrospective study of 475 asymptomatic women with dense breasts at Penn Medicine that subsequently published in the Journal of Clinical Oncology (DOI: 10.1200/JCO.19.02198), where Weinstein was the lead author, researchers used abbreviated MRI to detect roughly 27 cancers per 1,000 women screened. Inclusion of ductal carcinoma in situ (noninvasive or preinvasive cancer) in the calculation explains the higher cancer detection rate relative to the JAMA study, she adds.
Importantly, in studies comparing the abbreviated MRI to the full MRI, the abbreviated MRI yields a cancer detection rate “almost as good” as a full MRI, says Weinstein. In addition, the full MRI has repeatedly been shown to outperform breast screening ultrasound as a supplemental exam in head-to-head comparison studies.
While ultrasound will detect an additional two to three cancers missed by mammography in women with dense breasts, she continues, for every 100 biopsy recommendations, only about eight to 10 will be cancer. This means screening ultrasound detects many lesions that are not cancer.
For every 100 biopsies recommended by mammography, by comparison, about 25% to 30% turn out to be cancer. Screening ultrasound has the potential of “finding a lot of benign stuff and [unnecessarily] putting women through a lot of anxiety,” Weinstein says.
Several states—including Connecticut, New Jersey and Pennsylvania—now have laws stipulating that insurers cover supplemental screenings, including MRI, for women with dense breasts, she continues. The law took effect in Pennsylvania only a few months ago but may not translate into coverage until existing contracts with healthcare providers expire. It also only mandates coverage for women with extremely dense breasts, in whom mammogram sensitivity can be low as 50-60%.
The full MRI breast exam has been around for decades and, in addition to mammography, is specifically indicated for women at a greater than 20% lifetime risk of getting diagnosed with breast cancer, says Weinstein. Laws in 38 states and the District of Columbia stipulate that women be notified if they have heterogeneously dense or extremely dense breasts and the potential effect this can have on the sensitivity of mammography—the most validated screening test for breast cancer—in a lay summary of their mammogram report.
Approximately 50% of women in the U.S. have dense breasts, Weinstein says, and breast ultrasound is by far the most commonly chosen supplemental screening exam. Fear of getting a potentially false-positive result, and needlessly undergoing a biopsy, also dissuades some women from opting for a supplemental screening exam.
The sensitivity of mammography is very good for women with fatty and scattered fibroglandular densities, she adds. Supplemental screening may be beneficial for women with heterogeneously dense or extremely dense breasts, as defined by the Breast Imaging Reporting and Data System (BI-RADS).
Weinstein says it’s “still too early” to start advocating at the national level for abbreviated MRI as a supplemental screen for women with dense breasts. “We’re finding cancers that aren’t being picked up by mammography, but we don’t have any long-term [survival] data… to show what this all means.”
The Penn Medicine team, as well as the ECOG-ACRIN Cancer Research Group behind the JAMA study, both have follow-up studies planned to better understand the relationship between screening methods and clinical outcome. More data will be needed to provide the impact of abbreviated MRI on mortality, survival, and the degree of possible overdiagnosis.
Abbreviated MRI is already in high demand at University Hospitals (UH) Cleveland Medical Center, where the test has been offered since February 2018, according to Holly Marshall, M.D., division leader of breast imaging. Since then (through Dec. 7, 2020), 2,092 exams have been performed across 10 UH locations on over 1,700 patients with some patients opting for fast MRI every year.
Notably, the cancer detection rate among the population screened by abbreviated MRI at the UH system is 15 per 1,000, which is higher than outcomes reported from the ECOG-ACRIN study, Marshall says. A paper on the results will be submitted for publication, she adds.
Unlike at Penn Medicine, central scheduling doesn’t act as a gatekeeper to ensure only women with dense breast tissue are screened by fast MRI, says Donna Plecha, M.D., chair of the department of radiology. But the test is marketed to referring clinicians as being appropriate for patients with dense breasts interested in supplemental screening, and the majority of the published literature on abbreviated MRI is specific to dense-breasted women. Only one study to date, which appeared in Radiology (DOI: 10.1148/radiol.2016161444), has found it benefits normal-risk patients at every level of breast density.
No referred patients are refused the test, which costs $250 out of pocket—less than the insurance deductible for most of the women, says Plecha. As was seen with breast tomosynthesis, more research is necessary to convince insurance companies of its value.
It would take a randomized controlled trial with many women with over 15 years of follow-up to study the impact of fast MRI screening on long-term survival. Finding funding for that kind of trial is unlikely, says Plecha. “If we can prove that we are finding the more aggressive tumors earlier, the ones that invade into the blood vessels or are more likely to metastasize, then I think we can use that as a surrogate to improving survival,” she adds.
The rate of which abbreviated MRI is being adopted is unknown, but the how-tos of implementing the modality is a topic of growing interest, says Plecha, who has frequently spoken on the topic. Interest has been particularly high among referring clinicians whose patients had cancer detected by the imaging test at UH Cleveland Medical Center.
Acceptance of the modality is unquestionably high relative to screening breast ultrasound that has been offered for years by the institution and “just never took off,” Marshall adds. The latter study is less sensitive and has more negative biopsies associated with it.
“All of the locations where we offer fast MRI are filled far in advance,” notes Marshall. The utilization rate has leveled off but that’s due to limited appointment slots—not lack of enthusiasm for getting the exam.