The Importance of Treatment and Timing in Metaplastic Breast Cancer

Abstract

Metaplastic breast cancer (MBC) is a rare variant of breast cancer with high rates of locoregional recurrence and limited data available regarding patterns of care and treatment outcomes. We queried the National Cancer Data Base (NCDB) to examine the impact of clinical and treatment factors on overall survival (OS) in patients with metaplastic breast cancer. We identified patients in the NCDB diagnosed with MBC from 2004-2013 without metastatic disease, who received definitive management, and had complete information with regards to treatment and survival status. Univariate and multivariable Cox proportional hazard models were used to assess covariates related to OS. Actuarial analyses estimated survival rates. Chi-square tests and ANOVA were done to examine correlations between disease factors. Overall, 3,825 patients with MBC were identified. Of those with known clinical data, median age was 62 years old with a median tumor size of 3.0 cm, 83% were poorly differentiated, 63% were ER/PR/Her2 (triple) negative, and 18% were LN+. Forty-five percent underwent breast conservation therapy, and 55% underwent mastectomy. With respect to additional treatment, 49% received radiotherapy and 67% received chemotherapy, with 13% receiving neoadjuvant chemotherapy. At 5 and 10 years, the OS rates were 69.5% and 54.3%, respectively. On multivariable analysis, older age (HR=1.02, p<0.001), higher Charlson-Deyo Score (HR=1.48-2.14, p<0.001), larger tumor size (HR=2.15-3.35, p<0.001), LN+ disease (HR=1.34, p=0.029), neoadjuvant treatment (HR=1.56, p=0.001), higher pathologic stage (HR=1.87-3.37, p=0.001), positive margins (HR=1.65, p=0.017), and treatment without radiation (HR=1.63, p<0.001) or chemotherapy (HR=1.55, p<0.001) were significantly associated with worse OS. Patients receiving mastectomy were associated with significantly worse OS if they did not receive chemotherapy (HR=2.06, p<0.001). Those receiving radiation therapy had a worse OS (HR=0.83, p=0.04) however they also were significantly more likely to have a higher clinical/pathologic stage and/or LN+ disease. Those who underwent lumpectomy alone without radiotherapy (HR=2.53, p<0.001) or chemotherapy (HR=1.90, p<0.001) had significantly worse OS. Metaplastic breast cancer is a heterogeneous disease which is often triple negative. Receipt of radiation improves survival in patients undergoing lumpectomy while systemic therapy improves survival regardless of local therapy. Optimizing systemic therapy and radiotherapy may be associated with improved OS.