MRI detection of multi focal breast carcinoma: Report from the International Breast MRI Consortium

Reviewer: Charles Wood, MD
Abramson Cancer Center of the University of Pennsylvania
Last Modified: June 5, 2004

Presenter: M. D. Schnall
Presenter's Affiliation: University of Pennsylvania
Type of Session: Scientific

Background

Single institution studies have suggested that MRI more accurately determines the extent of cancer within the breast compared to mammography, increasing the ability to detect multi-focal disease and potentially alter the treatment approach
This study was undertaken to estimate the relative yield and positive predictive value of MRI and mammography with respect to addtional foci of cancer within the breast, and to compare the features of the cancer detected

Materials and Methods

This is a prospective study of 1004 women with suspicious clinical or mammographic findings undergoing MRI prior to biopsy of the index lesion
Patients were enrolled at 17 centers in the US, Canada, and Germany
In addition to characterizing the index lesion, any incidental lesions discovered by MRI or mammogram were noted; incidental lesions were defined as being at least 2cm from the index lesion with the rationale that this would be outside any reasonable surgical margin
All index lesions and any suspcious incidental lesions (BIRAD score 4 or 5) were biopsied

Results

428 out of 1004 women had index lesions diagnosed with cancer
At least one incidental lesion was detected by MRI in 103 women and by mammography in 36 women
78 out of 103 MRI-detected and 20 out of 36 mammography-detected incidental lesions were biopsied
No signicant differences between the positive predictive value of each technique, as 56 out of 78 (72% PPV) MRI-detected incidental lesions and 17 out of 20 (85% PPV) mammography-detected lesions were malignant
Estimated yield in detecting incidental malignant lesions (multi-focal disease) was significantly higher by MRI (17%) compared to mammography (7%)
The characteristics of MRI-detected cancers were no different than mammography-detected cancers with respect to histology or grade
The majority of incidental lesions detected only by MRI occured in women with increased breast densities

Author's Conclusions

MRI provides increased ability to detect multi-focal disease in women with breast cancer as compared to mammography
The positive predictive value of each technique was similar
the IBMC is considering the recommendation of including MRI evaluation of the breast as part of the standard work-up prior to biopsy

Clinical/Scientific Implications

MRI is a superior tool for detecting multi-focal lesions in women diagnosed with breast cancer. This finding can significantly impact on the recommended surgical proceedure. A simple lumpectomy may not be the appropriate surgery in these patients and more extensive resection or mastectomy may be the optimal approach. There was no follow-up reported to show a clinical effect from MRI evaluation, as this was not part of the study design. However, the relatively high yield of second cancer foci leads one to believe that the study might well imply clinical significance. Including MRI in the standard evaluation of the patient prior to biopsy would have significant financial implications and an ACR cost-benefit study is currently ongoing to address this issue.

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