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Dec. 9, 2004 — In women with breast lesions that are suspicious for cancer, based on clinical examination or mammography, performing a breast MRI has high sensitivity but only moderate specificity for detecting breast cancer, but does not necessarily eliminate the need for tissue sampling, according to a study in the Dec. 8 issue of the Journal of the American Medical Association.
Mammography is the primary imaging modality used to detect clinically occult breast cancer, according to background information in the article. However, mammography has limitations in both sensitivity and specificity that have led to exploration of other imaging techniques. Magnetic resonance imaging (MRI) has been evaluated for breast imaging because of its value for assessing soft tissues of the body. Previous research has indicated that additional lesions seen by MRI that are not visible on the mammogram have been reported to be present in between 27 percent and 37 percent of patients. The use of MRI to evaluate women with mammographically or clinically suspicious breast lesions who are undergoing biopsy has shown high potential.
David A. Bluemke, M.D., Ph.D., of Johns Hopkins University School of Medicine, Baltimore, and colleagues conducted a study to determine the accuracy of breast MRI in conjunction with mammography for the detection of breast cancer in patients with suspicious mammographic or clinical findings. The International Breast MR Consortium was conducted at 14 university hospitals in the United States and Europe from June 2, 1998, through Oct. 31, 2001. The study included 821 patients referred for breast biopsy based on suspicious mammographic, clinical or ultrasound findings. Patients had MRI examinations performed prior to breast biopsy; MRI results were interpreted at each site, with MRI investigators blinded to pathological results.
The researchers found that MRI correctly detected cancer in 356 of 404 cancer cases (ductal carcinoma in situ [DCIS] or invasive cancer), resulting in a sensitivity of 88.1 percent, and correctly identified as negative for cancer 281 of 417 cases without cancer, resulting in a specificity of 67.7 percent. MRI performance was not significantly affected by mammographic breast density, tumor histology, or menopausal status.
"In conclusion, MRI shows high sensitivity and moderate specificity for breast cancer. However, for lesions that are mammographically or clinically suspicious, tissue sampling of the breast may not be avoided with the use of MRI," the authors write.
Editor's Note: This study was funded by grants from the National Cancer Institute. Gadolinium contrast agents were provided by Amersham Health, Berlex Laboratories, and Bracco Diagnostics. Co-author Dr. Weatherall has received a research grant from Philips Medical Systems. Co-author Dr. Schnall has received a research grant from Siemens Medical Systems and has a royalty agreement with USA Instruments.
In an accompanying editorial, Monica Morrow, M.D., of the Fox Chase Cancer Center in Philadelphia, writes that whether MRI will result in a meaningful clinical benefit is an open question, and one that should have been answered prior to its widespread adoption.
"Even the performance of mastectomy does not eliminate the problem of local tumor recurrence, so it is unrealistic to believe that an additional imaging study will do so. Evidence of clinical benefit in terms of overall survival, disease-free survival, or quality of life is the established standard for new therapeutic modalities in breast cancer. When imaging studies are used to select therapy, the same rigorous standards must be applied."
"Perhaps a more important issue is whether MRI will allow identification of a subset of patients who require no breast irradiation, or perhaps only partial breast irradiation. Only a clinical trial can definitely resolve these issues. In the absence of trials with a clinical end point, breast cancer patients undergoing MRI should be advised that this step forward in technology may take them right back to the 1970s and result in a mastectomy for disease that can be controlled with radiation," Dr. Morrow writes.