Pathological assessment of the response of locally advanced breast cancer to neoadjuvant chemotherapy and its implications for surgical management.

The effectiveness of breast-conserving surgery for patients with locally advanced breast cancer (LABC) after neoadjuvant chemotherapy (NACT) is still a controversial issue, and variable incidences of locoregional failures have been reported. The present study was conducted to pathologically assess the response of LABC to NACT, and also to evaluate the efficacy of preoperative clinical examination and mammography in detecting these pathological changes. A total of 38 patients with LABC received NACT in the form of three cycles of fluorouracil/adriamycin/cyclophosphamide and were then subjected to a mastectomy. The residual tumors in the mastectomy specimens were measured, mapped, and compared to the pretreatment and preoperative clinical and mammographic findings for evaluation. An objective response to NACT was observed in 70.4% of the patients; however, only 26.7% of them were suitable candidates for conservative surgery. The rest of the responders showed an increased incidence of multifocality and in situ lesions localized within the original tumor-bearing area. Both clinical examinations and mammography were inadequate for the selection of candidates for breast conservation. Tumor regression by NACT is probably induced by a process of tumor segmentation. It is also associated with an increased incidence of multifocality and in situ lesions.