Defining an optimal role for breast magnetic resonance imaging when evaluating patients otherwise eligible for...

Pre-treatment breast magnetic resonance imaging (MRI) findings in a cohort of women prospectively evaluated for accelerated partial breast irradiation (APBI) are reviewed and characterized to determine the optimal use of MRI in these patients.

Candidates initially deemed eligible for a prospective APBI trial based on physical examination, mammography, and ultrasound (US) were further evaluated with breast MRI before treatment. All abnormal MRI findings were biopsied.

Between 2002 and 2011, 180 women who met inclusion criteria for APBI underwent breast MRI prior to treatment (median age=59; range 38-86). 126 tumors (70%) were invasive carcinomas with or without associated DCIS, while 54 (30%) were pure DCIS. Breast MRI confirmed unifocal disease in 109 patients with 111 cancers (60.5% of MRI cohort). Multifocal disease was identified in 19 patients (10.5% of MRI cohort), while multicentric disease was present in 3 patients (1.6% of MRI cohort). Five patients (4%) had an MRI-detected contralateral cancer. False positive MRI findings were seen in 45 patients (25% of MRI cohort). Pre-menopausal patients and patients with tumors >2 cm were more likely to have MRI-detected multifocal/multicentric disease. While there was no statistically significant correlation between multifocal/multicentric disease and breast density, tumor histology, grade, ER status, or Her2/Neu expression, numbers in each category were small, suggesting a lack of statistical power to detect differences that may be clinically meaningful. One hundred and fifty-two of the 180 patients (84.4%) successfully completed lumpectomy and APBI, while 6.7% of the cohort underwent mastectomy.

Breast MRI identified additional disease in 12% of APBI candidates. Premenopausal women and patients with tumors >2 cm were more likely to have MRI-detected multifocal/multicentric disease.