Metastatic inflammatory breast cancer: survival outcomes and prognostic factors in the national, multicentric, and real-life French cohort (ESME)

BACKGROUND Primary inflammatory breast cancer (IBC) is a rare and aggressive entity whose prognosis has been improved by multimodal therapy. However, 5-year overall survival (OS) remains poor. Given its low incidence, the prognosis of IBC at metastatic stage is poorly described. MATERIALS AND METHODS This study aimed to compare OS calculated from the diagnosis of metastatic disease between IBC patients and non-IBC patients in the Epidemiological Strategy and Medical Economics database (N = 16 702 patients). Secondary objectives included progression-free survival (PFS) after first-line metastatic treatment, identification of prognostic factors for OS and PFS, and evolution of survival during the study period. RESULTS From 2008 to 2014, 7465 patients with metastatic breast cancer and known clinical status of their primary tumor (T) were identified (582 IBC and 6883 non-IBC). Compared with metastatic non-IBC, metastatic IBC was associated with less hormone receptor-positive (44% versus 65.6%), more human epidermal growth factor receptor 2-positive (30% versus 18.6%), and more triple-negative (25.9% versus 15.8%) cases, more frequent de novo M1 stage (53.3% versus 27.7%; P < 0.001), and shorter median disease-free interval (2.02 years versus 4.9 years; P < 0.001). With a median follow-up of 50.2 months, median OS was 28.4 months [95% confidence interval (CI) 24.1-33.8 months] versus 37.2 months (95% CI 36.1-38.5 months) in metastatic IBC and non-IBC cases, respectively (P < 0.0001, log-rank test). By multivariate analysis, OS was significantly shorter in the metastatic IBC group compared with the metastatic non-IBC group [hazard ratio = 1.27 (95% CI 1.1-1.4); P = 0.0001]. Survival of metastatic IBC patients improved over the study period: median OS was 24 months (95% CI 20-31.9 months), 29 months (95% CI 21.7-39.9 months), and 36 months (95% CI 27.9-not estimable months) if diagnosis of metastatic disease was carried out until 2010, between 2011 and 2012, and from 2013, respectively (P = 0.003). CONCLUSION IBC is independently associated with adverse outcome when compared with non-IBC in the metastatic setting.