Pattern of distant metastases in inflammatory breast cancer - A large-cohort retrospective study

Inflammatory breast cancer (IBC) is a fatal form of breast cancer. IBC patients present with unfavorable prognosis mainly attributable to high risk of distant metastasis. Thus, in this cohort study, we aimed to explore metastatic profiles of different molecular subtypes of IBC and elucidate the clinical and prognostic characteristics among different metastatic sites. Patients diagnosed as IBC between 2010 and 2016 were identified from the Surveillance, Epidemiology and End Results (SEER) database. Chi-square tests were performed to compare metastatic distribution among different molecular subtypes. We further used odds ratio calculation to analyze the combined metastatic patterns. Kaplan-Meier methods and multivariate Cox regression models were applied to analyze survival data among different metastatic organs. In total, we enrolled 635 IBC patients between 2010 and 2014 as the training cohort and 242 IBC patients between 2015 and 2016 as the validation cohort, All the included patients were recorded with known metastatic status, follow-up data and molecular subtype. In the present study, we elaborated the following three points: (1) Elucidating the distribution of single-organ metastases in IBC. Bone and brain were the most and least common metastatic lesions for all subtypes of IBC, separately. (2) Clarifying the combined metastatic patterns and tendency of co-metastases. Bi-organ metastasis occurred most frequently among all combined metastases. Several combinations, such as liver and bone, lung and brain, were preferential for bi-organ metastasis. (3) Analyzing prognostic values of single-organ and bi-organ metastases. All single-organ distal metastases were independent risk factors indicating an unfavorable prognosis. In conclusion, our results would provide more information for clinical decision and future studies.