MRI May Help Find Missed Breast Cancers in High Risk Women
High False Positive Rate Must Be Considered
June 1, 2003
CHICAGO - New research presented today at the annual meeting of the American Society of Clinical Oncology finds that Magnetic Resonance Imaging (MRI) is a highly sensitive screening tool that may detect breast cancers missed by mammograms in women who are at increased risk for developing the disease. Researchers caution, however, that MRI also yields a significant number of false positive results, leading to additional exams that may have a negative psychological impact on women who are already anxious because of their elevated risk.
"MRI may improve the sensitivity of breast cancer surveillance for women at the highest levels of breast cancer risk, and ultimately could become an effective addition to the arsenal of tools we use to detect the disease," said the study's lead author Mark Robson, MD, medical oncologist at Memorial Sloan-Kettering Cancer Center (MSKCC).
Women with BRCA mutations are at higher risk than the general population for developing breast cancer. This study reports the results of breast MRI examinations in 54 BRCA-positive women who were part of a larger breast cancer surveillance program at MSKCC.
The women underwent 97 screening breast MRI examinations in addition to their routine mammograms between July 1998 and April 2003. Another 28 exams were performed as short-term follow-up examinations approximately six months after the previous MRI had detected a minor abnormality. Four more exams were performed either at the time of a contralateral breast cancer diagnosis, or before a prophylactic mastectomy.
During the study period, two of the 54 women developed ductal carcinoma-in-situ (a preinvasive breast condition) and one woman developed invasive breast cancer. All three women had reportedly normal mammograms within six months of their MRI. No woman on the study has yet developed cancer within 12 months of a normal MRI examination.
Although MRI was 100 percent sensitive for the detection of breast cancer, a significant number of women had abnormal examinations that were eventually shown not to represent cancer (false-positives). Further studies such as a repeat MRI at six months or a biopsy were recommended after 35 (36. 5 percent) of the 97 screening examinations and after 11 (39.3 percent) of the 28 short-term follow-up examinations. Altogether, biopsies were recommended after 21 (16.3 percent) of the 129 MRI studies. Only three biopsies (14.3 percent) resulted in a cancer diagnosis.
"MRI should not be recommended to the general population at the present time because its specificity is not yet adequate, and the majority of abnormalities detected in average risk women would turn out to be false-positives, many of which would need to be proven through additional examinations such as ultrasound, mammograms, and biopsies," cautioned Dr. Robson.
In addition, MRI has not yet been shown to reduce the size at which tumors are detected, to lower the stage of detected tumors, or to improve survival.
The authors concluded that further research is required to find ways to reduce the false-positive rate of breast MRI screening, define its psychological and economic impact on women with BRCA mutations, and obtain a clearer sense of its benefit before it can be made into a recommended screening tool.
In the meantime, the study investigators say specialists counseling women at genetically increased risk for developing breast cancer must continue to help them consider the pros and cons of breast MRI as a screening option for their individual circumstances.
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