Lack of efficacy to systemic chemotherapy for treatment of metaplastic carcinoma of the breast in the modern era.

Metaplastic carcinoma of the breast (MCB) is a rare subtype of breast cancer. Anecdotal reports are available regarding its response to systemic chemotherapy. We reviewed the records of patients diagnosed with MCB at National Taiwan University Hospital between 1988 and 2009. A total of 46 MCB cases were identified from 8,695 breast tumor patients who underwent biopsy or resection. About 11 of 25 patients with initial bulky disease (T3-4) received neoadjuvant chemotherapy before surgery, and 2 (18.2%) exhibited a partial response. About 12 of 18 patients who developed distant metastasis received palliative systemic chemotherapy. Of them, only 1 (8.3%), 1 (10%), and none (0%) responded to first-, second-, or third- and beyond line chemotherapy, respectively. None of the patients who received anthracyline- (n = 13), vinorelbine- (n = 7), or cyclophosphamide-based (n = 18) chemotherapy responded, whereas 3 (17.6%) of 17 patients who received taxane-based chemotherapy exhibited a partial response. Tumor response to systemic chemotherapy remains generally poor for MCB patients. Taxanes may have modest activity, but need to be validated in further studies.