Metastatic behavior and overall survival according to breast cancer subtypes in stage IV inflammatory breast cancer

Abstract

Abstract Background Distant metastatic disease is frequently observed in inflammatory breast cancer (IBC), with a poor prognosis as a consequence. The aim of this study was to analyze the association of hormone receptor (HR) and human epidermal growth factor receptor-2 (HER2) based breast cancer subtypes in stage IV inflammatory breast cancer (IBC) with preferential site of distant metastases and overall survival (OS). Methods For patients with stage IV IBC, diagnosed in the Netherlands between 2005 and 2016, tumors were classified into four breast cancer subtypes: HR+/HER2−, HR+/HER2+, HR−/HER2+, and HR−/HER2−. Patient, tumor, and treatment characteristics and sites of metastases were compared. OS of the subtypes was compared using Kaplan-Meier curves and the log-rank test. Association between subtype and OS was assessed in multivariable models using logistic regression. Results In total, 744 eligible patients were included: 340 (45.7%) tumors were HR+/HER2−, 148 (19.9%) HR−/HER2+, 131 (17.6%) HR+/HER2+, and 125 (16.8%) HR−/HER2−. Bone was the most common metastatic site in all subtypes. A significant predominance of bone metastases was found in HR+/HER2− IBC (71.5%), and liver and lung metastases in the HR−/HER2+ (41.2%) and HR−/HER2− (40.8%) subtypes, respectively. In multivariable analysis, the HR−/HER2− subtype was associated with significantly worse OS as compared to the other subtypes. Conclusion Breast cancer subtypes in stage IV IBC are associated with distinct patterns of metastatic spread and display notable differences in OS. The use of breast cancer subtypes can guide a more patient-tailored staging directed to metastatic site and extend of disease.