Comparison of the Diagnostic Accuracy of Magnetic Resonance Imaging with Sonography in the Prediction of Breast Cancer Tumor Size: A Concordance Analysis with Histopathologically Determined Tumor Size

In order to effectively treat patients with breast cancer, it is important to know the precise tumor size. We compared the rates of concordance of magnetic resonance imaging (MRI)-derived and sonography-derived breast cancer tumor size with histopathologically determined tumor size. Accuracy of MRI and sonography in establishing tumor size was evaluated by comparing preoperative images with postoperative pathologic findings. The accuracy of MRI and sonography was graded as concordance, underestimation, or overestimation and was compared in different subgroups. A total of 682 patients comprised the study cohort. Mean tumor size was 3.64 +/- A 1.8 cm via MRI, 2.12 +/- A 1.0 cm via sonography, and 2.78 +/- A 1.7 cm via pathologic examination. The difference between breast sonography and MRI to pathologic tumor field size was -0.68 +/- A 1.4, and 0.85 +/- A 1.25 cm, respectively (P < 0.001). Sonography had a concordance rate of 54.3 %, an overestimated rate of 9.8 %, and an underestimated rate of 35.9 %. For MRI, the concordance rate was 44.1 %, the overestimated rate was 52.5 %, and the underestimated rate was 3.4 %. In subgroup analysis, breast MRI had a higher concordance rate in patients with T3 (> 5 cm) lesions. When the results of MRI and sonography were considered together, the concordance rate increased from 54.3 to 62.2 %. MRI tends to overestimate the actual tumor size, while sonography frequently underestimates it. Combined sonography and MRI increases the accuracy of tumor size prediction.