Residual breast cancer diagnosed by MRI in patients receiving neoadjuvant chemotherapy with and without bevacizumab.

Purpose: To investigate the impact of antiangiogenic therapy with bevacizumab on pathological response and the diagnostic performance of magnetic resonance imaging (MRI) in breast cancer patients.

Methods: Thirty-six patients (aged 31-69 years) with breast cancer were included. Sixteen patients received neoadjuvant chemotherapy (NAC) containing bevacizumab, and 20 patients received the same NAC protocol without bevacizumab. Serial MRI studies were performed to evaluate response. All patients received surgery after completing NAC. The extent of residual disease was examined by histopathology, and classified into three types (pCR-pathologic complete response, confined nodules, and scattered cells). Fisher's exact test and general logistic regression models were applied to analyze differences between two groups.

Results: pCR rates and residual disease (nodular and scattered cell) patterns were comparable between the two groups. The diagnostic accuracy rate of MRI (true positive and true negative) was 13/17 (76%) for patients with bevacizumab, and 14/20 (70%) for patients without bevacizumab. The size measured on MRI was accurate for mass lesions that shrank down to nodules, showing <0.7 cm discrepancy from pathological size. For residual disease presenting as scattered cells within a large fibrotic region, MRI could not predict them correctly, resulting in a high false-negative rate and a large size discrepancy.

Conclusion: The pathological response and the diagnostic performance of MRI are comparable between patients receiving NAC with and without bevacizumab. In both groups MRI has a limitation in detecting residual disease broken down to small foci and scattered cells/clusters. When MRI is used to evaluate the extent of residual disease for surgical treatment, the limitations, particularly for nonmass lesions, should be considered.