MRI Detects Nearly All Contralateral Breast Cancers
A new study has demonstrated a significant benefit of adding a magnetic resonance imaging (MRI) study to the standard diagnostic workup following a new diagnosis of breast cancer in one breast.
By using MRI to examine the opposite breast in a population of 969 women with newly diagnosed breast cancer, researchers from the NCI-funded American College of Radiology Imaging Network (ACRIN) discovered 3.1 percent of the patients had cancers in the contralateral breast that were missed by standard practice mammography and clinical breast exam. A negative result on the MRI exam of the contralateral breast nearly eliminated the likelihood (0.3 percent) of cancer being found in that breast over the next year, they reported in the March 29 New England Journal of Medicine.
MRI demonstrated a 91-percent sensitivity (percentage of true cancers detected) and 88-percent specificity (percentage of true negatives), and MRI efficacy was not affected by patients' cancer type, age, or breast density.
"We can now identify the vast majority of contralateral cancers at the time of a woman's initial breast cancer diagnosis," said the study's principal investigator, Dr. Constance Lehman, professor of radiology and director of breast imaging at the University of Washington and Seattle Cancer Care Alliance.
Finding cancer in the opposite breast at this juncture will help avoid the cost, morbidity, and stress of multiple or delayed treatments, Dr. Lehman said. And a negative result on the opposite breast with mammography, clinical exam, and MRI also may allow women to forego prophylactic bilateral mastectomies, "a potential outcome that we would be delighted to see," she added.
The NCI-funded trial is the first of this size on the topic, with more than 1,000 patients enrolled, including those being treated at academic medical centers, community hospitals, and private practices. Adding a contemporaneous MRI to the diagnostic workup effectively doubled the number of contralateral cancers typically found. In 121 cases, MRI findings led to biopsies, 30 of which resulted in cancer diagnoses. Of these, 60 percent were invasive cancers, while the remainder were ductal carcinoma in situ (DCIS), abnormal cell clusters in the lining of the breast duct that have not invaded other tissue but that can progress to full-blown invasive tumors.
Three additional tumors - all DCIS less than 5 mm in size - were diagnosed upon analyses of mastectomy tissue samples.
That one of every four cases referred for biopsy based on the MRI turned out to be cancerous is an important finding, according to Dr. Carl Jaffe, chief of the NCI Cancer Imaging Program's Diagnostic Imaging Branch. With conventional mammography, that ratio is generally closer to one in six.
"So, relative to mammography, MRI was far more specific," Dr. Jaffe said. "These contralateral breasts would have been considered negative based on mammography and a clinical exam. This is important because treatment planning for these women would have been based on incomplete information on the full extent of the disease. That's why these results are so striking."
Dr. Christy A. Russell, co-director of the University of Southern California/Norris Comprehensive Cancer Center's Lee Breast Center, suggested that this study and others should be considered in the development of consensus guidelines related to the diagnostic evaluation of a woman with newly diagnosed breast cancer.
Because the use and practice of breast MRI is still evolving in the United States and is not available in all clinical settings, Drs. Jaffe and Russell indicated that some obstacles still remain to its wider adoption.
Although its use for breast screening has increased - e.g., as a follow-up to an abnormal mammogram - insurers generally do not cover MRI for screening the opposite breast. That could change, however, based on these study results.
And, as Dr. Jaffe pointed out, MRI machines specifically set up to do breast screenings - those that have a breast "coil" and in settings with the ability to perform biopsy - need to become more widely available.
To ensure the highest quality scan, Dr. Russell advised that women undergoing a diagnostic MRI go to a center that has an MRI machine appropriately equipped for breast imaging. She also advised having the screening procedure done at a facility with biopsy capability and experience.
If a suspicious lesion is found on the MRI, but the center is not equipped to do a biopsy, she explained, then the woman will have to be referred to another center and repeat the entire imaging procedure to guide the biopsy.
By Carmen Phillips
NCI Cancer Imaging Program
NCI Research on Cancers in Women: Breast Cancer
NCI Cancer Topics: Breast Cancer