Metaplastic breast cancer: prognosis and response to systemic therapy

Metaplastic breast cancer is a rare disease with little information available to guide therapy. The goals of this study were to describe the patient characteristics, systemic therapies and clinical outcomes of all patients with primary metaplastic breast cancer treated at Mayo Clinic between 1976 and 1997.

Patients were identified through the medical index of Mayo Clinic. Clinical information was abstracted from the medical record of each patient. A literature search using MEDLINE and CANCERLIT for the years 1966-1997 was performed to identify all previously reported case series in the English language containing 10 or more patients.

Twenty-seven patients were identified with a median age at diagnosis of 59 years (range 39-90 years). The median tumor size was 3.4 cm (range 0.5-7.0 cm). One patient had metastatic disease at presentation. Twenty-three patients had information available on nodal status, estrogen receptor (ER) and progesterone receptor (PR) status. Twenty patients (87%) were node-negative and three patients (13%) were both ER and PR positive. Disease-free survival (DFS) and overall survival (OS) were assessed for those who presented with local-regional disease. The three-year DFS was 40% (95% CI: 23%-73%) and the three-year OS was 71% (95% CI: 51%-97%). In univariate analysis, those patients 60 years of age or older at diagnosis were found to have an increased DFS (P = 0.011). Among those with prior estrogen use, both DFS (P = 0.022) and OS (P = 0.003) were decreased. Thirteen patients (50%) developed metastases with a median DFS time of 2.4 years. Ten different chemotherapy regimens were utilized for metastatic disease and one partial response was observed. There were no responses to tamoxifen in four patients with metastatic disease. Median survival after the development of metastases was eight months.

Despite presenting more commonly as node-negative disease, DFS and OS in metaplastic breast cancer is decreased compared to typical adenocarcinomas. Systemic therapy also appears to be less effective. Patients with metaplastic breast cancer, particularly those with metastatic disease could be appropriate candidates for innovative therapeutic regimens.