Metaplastic Breast Cancer: To Radiate or Not to Radiate?

Background. The role of radiation therapy (RT) is unclear for metaplastic breast cancer (MBC). We hypothesized that RT would improve overall survival (OS) and disease-specific survival (DSS). Materials and Methods. We used the Surveillance, Epidemiology, and End Results (SEER) database to identify MBC patients diagnosed from 1988 to 2006. Univariate analyses of patient, tumor, and treatment-specific factors on OS and DSS were performed using the Kaplan Meier method and differences among survival curves assessed via log rank. Variables assessed included patient age, race/ethnicity, histologic subtype, tumor grade, T stage, N stage, M stage, hormone receptor status, surgery type, and use of RT. Cox proportional hazards models used all univariate covariates. Risks of mortality were reported as hazard ratios (HR) with 95% confidence intervals (95% CI); significance was set at P <= 0.05. Results. Among 1501 patients, RT was given to 580 (38.6%). Ten-year OS and DSS were 53.2, and 68.3%, respectively. In the overall analysis, RT provided an OS (HR 0.64; 95% Cl, 0.51-0.82; P < 0.001) and DSS (HR 0.74; CI, 0.56-0.96; P < 0.03) benefit. When patients were stratified according to type of surgery, RT provided an OS but not a DSS benefit to lumpectomy (HR 0.51; Cl, 0.32-0.79, P < 0.01) and mastectomy patients (HR 0.67; CI, 0.49-0.90; P < 0.01). Conclusions. Our findings support the use of RT for patients with MBC following lumpectomy or mastectomy. These retrospective findings should be confirmed in a prospective clinical trial.