Accuracy of MR imaging for revealing residual breast cancer in patients who have undergone neoadjuvant chemotherapy.
Our study investigated the usefulness of contrast-enhanced MR imaging for accurately measuring the size of residual tumor after patients have undergone neoadjuvant (pre-operative) chemotherapy. The imaging analysis method was optimized for identifying residual disease in the treated breast. Tumor sizes measured on the MR images and at the clinical examination were compared with the size of residual disease measured at pathology after surgery. Before undergoing surgery, 52 patients were imaged before and after receiving neoadjuvant chemotherapy. For each patient, specific malignancy criteria were applied to MR images before chemotherapy to identify the location of tumor, and residual disease was then identified as any remaining enhancement in the same area on the MR images after chemotherapy. Residual tumor size was measured using both the MR technique and the clinical examination findings, and the degree of measurement error for each method was assessed in comparison with the pathologic findings. The correlation with pathology was an r value of 0.89 for MR measurements compared with an r value of 0.60 for clinical measurements. In addition, MR imaging revealed all cases of residual disease, whereas clinical assessment resulted in five false-negative interpretations in the 52 treated lesions. The high correlation between measurements of residual disease obtained on MR images and those obtained at pathology validates the sensitivity of MR imaging of the breast after chemotherapy.