Preoperative Evaluation of Residual Tumor Extent by Three-Dimensional Magnetic Resonance Imaging in Breast Cancer Patients Treated with Neoadjuvant Chemotherapy

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Abstract
The purpose of this study was to evaluate the usefulness of three‐dimensional magnetic resonance imaging (3D MRI) for the preoperative assessment of residual tumor extent in breast cancer patients treated with neoadjuvant chemotherapy (NAC). Thirty‐eight breast cancer patients treated with NAC containing taxane and/or anthracycline for 3–6 months were enrolled in this study. Tumor size was measured by means of calipers, ultrasonography, and dynamic MRI before and after NAC. Three‐dimensional maximum intensity projection MRIs to measure the tumor size were created for every case. The tumor size determined by calipers, ultrasonography, and 3D MRI after NAC was compared with that determined by pathologic examination. The tumor size determined by 3D MRI showed a strong correlation with that determined by pathologic examination (r = 0.896). Moderate, but significant correlations were found between measurements obtained with calipers and pathology (r = 0.554), and between ultrasonography and pathology (r = 0.484). The response rates to NAC were estimated at 84.2% with calipers, 58.0% with ultrasonography, and 44.7% with 3D MRI. Calipers and ultrasonography thus tended to overestimate the response to NAC compared to 3D MRI (p < 0.001 and 0.240, respectively). Three‐dimensional MRI can visualize residual tumor extent after NAC more accurately than calipers and ultrasonography, and seems to be more reliable than other modalities for estimating response to NAC. It should also help surgeons with decision making for breast‐conserving surgery after NAC