A recent report in the New England Journal of Medicine found that, in 3 percent of 969 women with newly diagnosed cancer in one breast, MRI scans were able to detect malignant tumors in the other breast, even though clinical exam and mammography showed no abnormalities.
These results clearly indicate the advantage of MRI on the opposite breast at the time of a diagnosis of breast cancer. Finding a site of malignancy in the other breast at that time would allow a single round of treatment and eliminate the need, for example, for two separate bouts of chemotherapy. On the other hand, a negative MRI of the opposite breast provides almost complete assurance that that breast is free of cancer.
One considerable downside, however: MRI can detect such small abnormalities that 75 percent of the women in the study underwent biopsies that were negative, and thus not needed.
Should MRI replace mammography for most women? The answer is no. In addition to leading to unnecessary breast biopsies, the cost of MRI is high — about $2,000 compared with approximately $100 to $150 for mammography. But MRI should indeed be considered by women at the highest risk for breast cancer, such as:
- women with a strong family history of breast cancer; i.e., two or more close relatives with breast or ovarian cancer, or a close relative who developed breast cancer before the age of 40.
- women with a mutation in the BRAC1 or BRCA2 gene, or prior chest radiation for Hodgkin's disease.
MRI might also be considered for women whose breast tissue is so dense that it interferes with the ability of mammography to detect small cancers. Even those who elect to have MRI should also have mammography, which is better than MRI at discovering calcium deposits in the breast.
According to officials at the American Cancer Society, a patient should choose an MRI site carefully; that is, the MRI should be done at a clinic that has the expertise and equipment to carry out an MRI-guided biopsy.
