Breast Magnetic Resonance Imaging As It Is, in Contrast to How We Wish It to Be
Authors: Richard J. Bleicher
Journal: Journal of Clinical Oncology (2014)

There is perhaps no imaging, laboratory, or other study in modern breast care that has become more contentious or emotionally debated than breast magnetic resonance imaging (MRI). The first study on this modality in breast cancer was published 30 years ago. Since that time, breast MRI has had its share of supporters and detractors, and the meta-analysis that accompanies this editorial may unfortunately be either celebrated or reviled in various circles, depending on one’s stance or hopes for the modality. Irrespective of one’s thoughts about the promise of MRI (or lack thereof), the study’s significance lies in the fact that now, more than ever, today’s costconscious health care world dictates that we must demonstrate improved outcomes (or some other substantial benefit) to justify costs. The study by Houssami et al is the first meta-analysis to evaluate local and distant recurrence in individuals undergoing preoperative MRI who underwent at least an attempt at breast conservation, compared with those who did not have an MRI preoperatively. The study is an effort to consolidate and more definitively investigate a field of data that is comprised of small retrospective studies and prospective trials that have short published follow-up. Using individual patientlevel data (as opposed to pooled published data) to potentially reduce publication bias, the meta-analysis notes no improvement in local or distant recurrence associated with the modality. In short, the authors concluded that routine use of MRI preoperatively does not reduce the risk of ipsilateral local or distant recurrence and, with that in mind, MRI should not be used routinely in the preoperative setting. This study could face challenges in that the authors were unable to obtain data from all eligible studies, that not all studies evaluating MRI provide recurrence data or comparison (no MRI) cohorts, making them ineligible for analysis, and that for those studies included, there was short overall follow-up. These caveats suggest that continued evaluation of the modality remains appropriate, but considerable data on MRI to date have not shown the promise in the routine preoperative setting for which many have hoped. Although the recurrence data that are presented here may be disappointing, we must not ignore a growing body of literature that overwhelmingly reaches the same conclusion. Breast MRI, like so many other tests, has advantages for particular clinical scenarios, but not as a routine, reflexively ordered test to be used in all cancer patients preoperatively. Although this meta-analysis adds significant strength to a body of literature, several hopes for MRI in the nonhigh-risk setting had already been dashed before this publication. There has been little suggestion, even among strong routine-MRI advocates, that the modality could improve survival. This is because breast conservation therapy has long had survival equivalent to mastectomy—well before MRI was even used. Thus, the possibility that MRI could improve on lumpectomy by making survival better than that achieved via mastectomy is nearly nonexistent. Volumes of data have also found that surgical improvements in technique are not improved by MRI, and so now, with doubts cast on its ability to improve local or distant recurrence as well, the prospects for justifying the modality’s routine preoperative use in the nonhigh-risk setting have nearly disappeared. However, ultimately, when readers review the MRI meta-analysis by Houssami et al, they will ask themselves: do the data make sense? We have a modality that is more accurate for judging lesion size and more sensitive for detecting otherwise subclinical cancer foci, and yet MRI series demonstrate no improvement in our ability to perform breast conservation, and now, no ability to lower the recurrence rate. Viewed solely in that light, the data do not at first seem to make sense, but this assumes that MRI enables us to rid a significantly greater amount of disease from the breast than we could otherwise, that such disease is clinically significant and requires resection, that systemic therapy and radiotherapy add little to surgical removal, and that MRI provides a sufficiently accurate depiction of the cancer to reliably assist the surgeon. Although the idea conflicts with our instinctive fear of cancer, not all disease is clinically significant, and not all breast cancer requires resection because of our multimodal therapy paradigm. The most recent example of this in a prospective study was for the axilla in the American College of Surgeons Oncology Group Z0011 trial, in which 30% of patients with undissected positive nonsentinel nodes in the observation arm developed no increase in recurrence or difference in overall survival. The breast is subject to a similar effect. Before MRI was in frequent use, radiotherapy was established as critical to reduce local recurrence in breast conservation, and, initially, we could only speculate as to why. Then along came breast MRI, making multifocal and multicentric disease visible, and confirming what had been forgotten about mastectomy studies: that multiple foci exist in the breast in up to 63% of tumors, even when not visible on mammography. These foci have been treated reasonably well for decades, long before we could so easily see them with MRI, although understandably, simply knowing that cancer is present does not frighten us nearly as much as actually seeing it on film. But recurrence rates, even without the use of MRI, are now merely 2% to 4% at 5 years because of radiotherapy and systemic JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 32 NUMBER 5 FEBRUARY 1