The role of body mass index at diagnosis in patients with inflammatory breast cancer

Introduction: Inflammatory Breast Cancer (IBC) is an aggressive presentation of BC present in 1–5 % of all patients with BC. While obesity has been consistently associated with worse prognosis in patients with BC, it is understudied in patients with IBC. Patients and methods: We retrospectively evaluated the association of body mass index (BMI) at diagnosis with clinicopathological characteristics, pathological complete response (pCR) to chemotherapy and survival in a multicentric cohort of patients with IBC treated with pre-operative chemotherapy. Results: Of the 542 patients, 6 were underweight (1.1 %, excluded in further analysis), 190 were normal-weight (35.1 %), 187 had overweight (34.5 %), and 159 had obesity (29.3 %). Of the 536 included patients, 463 had non-metastatic and 73 metastatic IBC at diagnosis. Higher BMI was associated with older age at diagnosis, increased stromal tumor infiltrating lymphocytes (sTIL), and particularly in the ER-/HER2+ subgroup, a greater likelihood of metastasis at diagnosis. Tumor emboli were less frequently detected in peritumoral samples of patients with obesity as compared to patients with normal weight. Among non-metastatic patients, those with obesity in the ER-/HER2+ and ER+/HER2-subgroups showed numerically, but not statistically significantly, lower rates of pCR following neoadjuvant chemotherapy than normal-weight patients (38.5 % vs 42.5 %, and 6.6 % vs 16.7 %, respectively). BMI was not associated with any survival endpoint. Conclusion: We observed a limited association of BMI with clinicopathological variables and pCR in patients with IBC without evidence of its relationship with survival outcomes. Future studies should investigate the biological impact of obesity on IBC and its tumor microenvironment.