Metaplastic breast cancer: to radiate or not to radiate?

Abstract

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). 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. 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% CI, 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; CI, 0.32-0.79, P < 0.01) and mastectomy patients (HR 0.67; CI, 0.49-0.90; P < 0.01). 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.