An Institutional Review of Treatment Outcomes for Metaplastic Breast Cancer

Abstract

Purpose/Objective(s): Metaplastic breast cancer is a rare type of breast cancer, associated with poor prognosis, and exhibits heterogeneity in presentation and outcome. There are conflicting reports on the significance of specific histopathology on clinical outcome. The goal of this study was to analyze clinical outcomes in metaplastic breast carcinoma and any potential association with histologic subtypes. Materials/Methods: With IRB approval, single institution data were obtained for all patients diagnosed with non-metastatic, metaplastic breast cancer between 2002 and 2013. All cases were re-evaluated by dedicated breast pathologists and confirmed as metaplastic breast cancer. Histologic subtype was divided into four categories: spindle, squamous, matrix-producing, and other. Demographic information and clinical presentation were correlated with histologic subtype. Univariate and multivariate Cox proportional hazards models were performed to evaluate the impact of histologic variables on outcome. Kaplan Meier methods evaluated localrecurrence-free and distant-metastasis-free survival. Results: One hundred thirteen female patients with non-metastatic, metaplastic breast cancer were identified, all of whom underwent needle core or excisional biopsy followed by surgical resection. Median age was 60 and median follow up was 31 months. The majority of patients received chemotherapy and/or radiation (74% and 54%, respectively). Only 46/113 (41%) were identified to have metaplastic breast cancer at the time of initial biopsy. At resection, 94% were Bloom Richardson grade III and 67% were triple negative. Among the 113 patients, the following histologic subtypes were observed: 14 (12%) spindle, 51 (45%) squamous, 32 (27%) matrix-producing, and 18 (16%) other. There was no difference in the frequency of T and N stage observed at presentation among different histologic subtypes (pZ0.4 and 0.17, respectively). Univariate analysis demonstrated that histologic subtype did not significantly correlate with local (pZ0.54) or distant (pZ0.83) control. Two year local control rates per Kaplan Meier analysis are as follows: spindle 77%, squamous 90%, matrix-producing 97%, and other 97%, with no statistically significant difference among subtypes (pZ0.53). For the same histologic subtypes, 2 year distant-metastasis-free survival rates were 84%, 87%, 86%, and 81%, respectively (pZ0.83). Conclusion: This study represents one of the largest reported experiences of the role of histologic subtype on outcomes in metaplastic breast cancer. Metaplastic breast cancer is infrequently diagnosed at biopsy. The majority are high grade and triple negative. Histologic subtype does not significantly impact rates of local recurrence or distant metastasis. Author Disclosure: C.A. Berriochoa: None. C.M. Leyrer: None. S. Agrawal: None. A. Donaldson: None. R. Stewart: None. H. Moore: None. R.D. Tendulkar: None. B. Calhoun: None.