SEATTLE -- Three percent of new breast cancer patients also have mammographically occult malignant tumors in the contralateral breast that can be detected only by magnetic resonance imaging, researchers reported.
SEATTLE, March 28 -- Three percent of new breast cancer patients also have mammographically occult malignant tumors in the contralateral breast that can be detected only by magnetic resonance imaging, researchers reported.
Among 969 women with a recent diagnosis of unilateral breast cancer and no abnormalities on mammography and clinical examination of the other breast, MRI found that 30 (3.1%) women had cancer in that breast nonetheless. The MRI-detected contralateral tumors were small and all were node negative.
The mean diameter of the invasive tumors detected was 10.9 mm. Forty percent of the MRI-detected malignancies were ductal carcinomas in situ (4 mm or smaller in diameter).
So reported Constance Lehman, M.D., Ph.D., of the University of Washington here, and colleagues in the American College of Radiology Imaging Network (ACRIN) trial, which was published in the March 29 issue of the New England Journal of Medicine.
In all, MRI led to biopsies in 121 of the 969 women (12.5%), and found 30 with positive lesions (24.8%). MRI also detected suspicious lesions in the contralateral breast that turned out to be benign in 91 other women.
Women with a fresh diagnosis of breast cancer should have an MRI of the contralateral breast prior to treatment of the initially discovered tumor, the investigators concluded.
The current cost of MRI precludes its widespread use for screening, but this imaging tool appears to improve the detection of cancer in women at increased risk (carriers of the breast cancer mutations, for example) and those with a recent diagnosis of breast cancer, Dr. Lehman's team concluded.
Historically, Dr. Lehman and colleagues said, 10% of women eventually develop a malignancy in the contralateral breast after treatment for unlilateral breast cancer.
They said that women at high risk for breast cancer, either because they already have the disease, have been recently diagnosed, or have a family history of breast cancer, should have MRI screening, which focuses on millimeter tissue slices rather than beaming through dense tissue in search of a tumor, the researchers said.
The new study was conducted at 25 sites in the U.S. and Canada, from academic centers to community practices. The sensitivity of MRI was 91% and the specificity, 88%, while the negative predictive value of MRI was 99%, the researchers reported.
The specificity was significantly higher among postmenopausal women than among premenopausal or perimenopausal women (91% versus 84%, P= 0.002). Similarly the positive predictive value was higher in the postmenopausal group (31% versus 11%).
The increased rate of detection of cancer came with a false positive rate of 10.9% and a relatively low risk of detecting benign disease on biopsy (9.4%), the investigators said.
The number of cancers detected was not influenced by breast density, menopausal status, or the histologic features of the primary tumor.
Among the advantages of diagnosing the contralateral cancer at the same time as the initial treatment is that woman can have a single round of treatment, the investigators noted.
They also pointed out that some women with a diagnosis of unilateral breast cancer choose prophylactic mastectomy of the opposite breast. Although the 88% specificity is lower than might be acceptable in screening programs, the high negative findings on a preoperative MRI might be acceptable to women concerned about undetected disease and could reduce the number of unnecessary mastectomies, Dr. Lehman and colleagues said.
The results of this study should be widely applicable because the participating sites represented a range of radiology practices, from and a wide range of interpreting MRI studies, from extensive to moderate experience, the researchers said.
In an accompanying editorial, Robert A. Smith, Ph.D., of the American Cancer Society in Atlanta discussed the evolving role of MRI in breast cancer detection.
The American College of Radiology's practice guideline for breast MRI outlines 12 clinical applications of MRI in the evaluation of breast disease. Now coincident with this issue of the NEJM, the society is publishing new recommendations for breast-cancer screening in women at high risk for breast cancer.
In its earlier 2003 update to its guideline for breast-cancer screening, the society concluded that women at increased risk for breast cancer might benefit from the earlier screening, shorter screening intervals, or the addition of screening methods such as breast ultrasound or MRI.
On the basis of newer evidence, as well as requests from clinicians for greater guidance in the use of breast MRI, the guidelines now recommend annual breast-cancer screening by means of MRI for women with an approximately 20% or greater lifetime risk of breast cancer. This is estimated according to risk models that are largely dependent on a strong family history of breast or ovarian cancer and who are known or likely carriers of the breast cancer mutations.
Annual MRI screening is also recommended for women who have undergone radiotherapy to the chest for Hodgkin's disease.
The updated guidelines also state that there is insufficient evidence to make a recommendation for or against MRI screening among women with a personal history of breast cancer, carcinoma in situ, or atypical hyperplasia, or in women with extremely dense breasts.
Although MRI is not available in every setting, its use will probably increase, Dr. Smith said. This year, he said, the American College of Radiology is likely to initiate a voluntary accreditation program for breast MRI similar to its current programs for mammography and breast ultrasound.
The original mammography goal of providing women in every community with high-quality mammographic evaluation, should be achieved for any imaging procedure used in the diagnosis of breast disease, Dr. Smith concluded.