Rethinking Preoperative Breast Magnetic Resonance Imaging.

Although magnetic resonance imaging (MRI) is exquisitely sensitive for detecting breast cancer, its precise clinical benefit in the routine preoperative setting is uncertain, and determinationof itsappropriateuse todatehasbeenchallenging.1 Early randomized prospective trials were hindered by low numbers, wide variation in imaging quality, and inconsistencies in incorporating MRI findings into treatment planning. Larger, more recent, retrospective trialshave reportedcorrelationsbetweenuseofbreast MRI and increased mastectomy rates but have been significantly limited by not controlling for key variables that are independentlyassociatedwithmastectomyrates.2-4Womenwho undergo preoperative MRI comprise a distinct subset of patients: theyaremore likely tobeyoung, athigh risk,havedense breast tissue, have genetic mutations, have more aggressive tumor subtypes, be seen at academic subspecialized centers thatoffer advanced reconstructive surgical techniques, andbe in ahigher socioeconomic status group than thosewhodonot undergo MRI. These factors themselves are known to be associatedwith higher rates ofmastectomies2,5; thus, failure to control for these variables is a significant limitation of retrospective studies seekingmeaningful correlationsbetweenMRI use and outcomes. Most important, correlation does not imply causation. In this issueof JAMAOncology, Arnaout et al6 evaluate the utilization of preoperative breast MRI. Using a populationbased cancer registry in Ontario, Canada, to identify incident breast cancers in thepreoperative setting, the authors6 found that preoperative MRI was performed in less than 15% of all patients diagnosed ashavingbreast cancer. The authors6 confirmedwhatothershavereported:womenwhounderwentpreoperative breast MRI were more likely to be young, at higher socioeconomic status, anddiagnosedashaving invasive lobular cancers at higher stage comparedwithwomenwhodidnot receive MRI. Patients seen at teaching hospitals or by surgeonswithhighervolumeswhomorerecentlycompletedtraining were more likely to undergo breast MRI. They6 also found differences in short-term surgical outcomesbetweenpatientswhounderwentbreastMRIand those who did not, including longer wait-times between diagnosis and surgery, higher rates of additional imaging and/or biopsies prior to surgery, and higher rates of ipsilateral and contralateralprophylacticmastectomy.Recognizingthat theseoutcomes aredependent onpatient, surgeon, and systemfactors, the authors6 controlled for some variables, such as socioeconomic status, age, tumor histologic type, patient comorbidity, surgeon experience, and the environment (academic vs community-basedpractice) inwhichapatientwas treated.Unfortunately, theauthorswerenotable tocontrol forgeneticmutation status, family history, or breast density. The authors6 suggest that rising breastMRIuse inwomen newly diagnosed as having breast cancer may contribute to a general problem of breast cancer overtreatment by prompting unnecessary additional imaging tests, biopsies, andmastectomies either in the affected breast or the unaffected contralateral breast. Because abnormalities identified on breast MRI require samplingprior todefinitive treatment, it isnot surprising that preoperative breastMRI prompts additional tests and biopsies, which in turn can lead to longer wait times between diagnosis and surgery. Furthermore, because MRI detectsmammographicallyoccultmulticentricdisease in roughly 10% of patients, and mastectomy is currently indicated for women with multicentric disease, it is logical that mastectomy rates would rise with its use. Finally, it is reasonable to believe that additional procedures resulting from falsepositive examinations could result in higher patient anxiety, tipping the scales toward more mastectomies. However, it is important to interpret the outcomes associatedwithobtainingpreoperative breastMRI from this study with some caution. Because the authors6 did not report MRI results (eg, if the MRI was interpreted as positive or negaRelated article page 1238 Opinion Editorial