The use of MRI before breast surgery is increasing based on reports that show that MRI can detect previously unknown foci of breast cancer in a substantial number of women with a new diagnosis of breast cancer. However, some argue that MRI will increase the proportion of mastectomy because it will cause more extensive surgeries. Since breast conservation surgery combined with radiation therapy as major advantages with similarly low recurrence rates and equivalent mortality, an increase in the rate of mastectomy prompted by MRI findings would be a negative development. Since studies have shown equivalent outcomes for lumpectomy with radiation and mastectomy, the implied argument is that the MRI just cause more extensive surgeries and not improve the results. Even if some foci are missed, preoperative MRI would have little or no impact on rates of recurrence or death because of post-operative radiation. For this reason, MRI should not be used routinely in the workup of new breast cancers.
At this time the effectiveness of radiation in eradicating residual foci of disease as compared to its surgical removal, is not known. Detecting widespread disease can obviate inappropriate attempts at conservation. Knowledge of the extent of disease can help patients select the most appropriate treatment options. A staging MRI examination showing only a single cancer lesion may permit the patient to choose conservation therapy with a high degree of confidence that no macroscopic disease will be missed at surgery.
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