OBJECTIVE: To assess the role of magnetic resonance imaging (MRI) in the planning of breast cancer treatment strategies. MATERIALS AND METHODS: The study included 160 women diagnosed with breast cancer, who underwent breast MRI for preoperative staging. Using Pearson's correlation coefficient (r), we compared the size of the primary tumor, as determined by MRI, by conventional imaging (mammography and ultrasound), and in the pathological examination (gold standard). The identification of lesions not identified in previous examinations was also evaluated, as was its influence on treatment planning. RESULTS: The mean age of the patients was 52.2 years (range, 30–81 years), and the most common histological type was invasive ductal carcinoma (in 60.6% of the patients). In terms of the tumor size determined, MRI correlated better with the pathological examination than did mammography (r = 0.872 vs. 0.710) or ultrasound (r = 0.836 vs. 0.704). MRI identified additional lesions in 53 patients (33.1%), including malignant lesions in 20 (12.5%), which led to change in the therapeutic planning in 23 patients (14.4%). CONCLUSION: Breast MRI proved to be more accurate than conventional imaging in determining the dimensions of the main tumor and was able to identify lesions not identified by other methods evaluated, which altered the therapeutic planning in a significant proportion of cases.

Keywords: Breast neoplasms; Neoplasm staging; Magnetic resonance imaging.