Abstract
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.