The selective use of preoperative MRI in the staging of breast cancer: a single-institution experience.

INTRODUCTION Routine use of preoperative breast magnetic resonance imaging (MRI) for loco-regional staging of breast cancer remains controversial. At Counties Manukau District Health Board (CMDHB), preoperative breast MRI is used selectively within a multidisciplinary setting. The purpose of this study is to determine the accuracy of selective use of preoperative MRI in staging loco-regional disease and how it has impacted our clinical practice. METHODS Patients who received preoperative MRI at CMDHB between October 2015 and October 2018 were identified on a prospective database. The decision to offer MRI was made by multidisciplinary consensus. Patient data were collected retrospectively from clinical, imaging and histology records. The accuracy of MRI was determined by comparing it against histology as gold standard, and its potential contribution to treatment decisions and treatment delay was determined by clinical record review. RESULTS Ninety-two patients received preoperative MRI. Additional foci of cancer were identified in ten patients (11%). Sixteen patients (17%) required additional biopsies. In fourteen patients (15%), MRI identified more extensive disease than conventional imaging prompting a change of surgical management. This 'upstaging' was confirmed histologically in twelve (13%). In one (1%) patient, MRI incorrectly 'downstaged' disease, but it did not alter the management. No patients experienced a delay in treatment due to MRI. CONCLUSION A selective, considered use of preoperative MRI within a multidisciplinary setting at our local institution results in more biopsies but with an acceptable risk-benefit ratio. It provides accurate staging to aid treatment decisions without resulting in a delay in treatment.