Pathologic complete response and overall survival in breast cancer subtypes in stage III inflammatory breast cancer

Purpose To analyze the influence of hormone receptors (HR) and Human Epidermal growth factor Receptor-2 (HER2)-based molecular subtypes in stage III inflammatory breast cancer (IBC) on tumor characteristics, treatment, pathologic response to neoadjuvant chemotherapy (NACT), and overall survival (OS). Methods Patients with stage III IBC, diagnosed in the Netherlands between 2006 and 2015, were classified into four breast cancer subtypes: HR+/HER2− , HR+/HER2+ , HR−/HER2+ , and HR−/HER2− . Patient-, tumor- and treatment-related characteristics were compared. In case of NACT, pathologic complete response (pCR) was compared between subgroups. OS of the subtypes was compared using Kaplan–Meier curves and the log-rank test. Results 1061 patients with stage III IBC were grouped into subtypes: HR+/HER2− (N = 453, 42.7%), HR−/HER2− (N = 258, 24.3%), HR−/HER2+ (N = 180,17.0%), and HR+/HER2+ (N = 170,16.0%). In total, 679 patients (85.0%) received NACT. In HR−/HER2+ tumors, pCR rate was highest (43%, (p < 0.001). In case of pCR, an improved survival was observed for all subtypes, especially for HR+/HER2+ and HR−/HER2+ tumor subtypes. Trimodality therapy (NACT, surgery, radiotherapy) improved 5-year OS as opposed to patients not receiving this regimen: HR+/HER2− (74.9 vs. 46.1%), HR+/HER2+ (80.4 vs. 52.6%), HR−/HER2+ (76.4 vs. 29.7%), HR−/HER2− (47.6 vs. 27.8%). Conclusions In stage III IBC, breast cancer subtypes based on the HR and HER2 receptor are important prognostic factors of response to NACT and OS. Patients with HR−/HER2− IBC were less likely to achieve pCR and had the worst OS, irrespective of receiving most optimal treatment regimen to date (trimodality therapy).