Reproductive Risk Factors of Inflammatory Breast Cancer according to Luminal, HER2-Overexpressing, and Triple-Negative Subtypes: A Case Comparison Study

Objective: We evaluated the risk factors of inflammatory breast cancer (IBC) compared to non-IBC and according to histological subtype. Methods: Cases of IBC (n = 160) and controls of non-IBC (n = 580) were collected from the cohort of breast cancer patients treated in two oncology centers matched based on age at cohort entry. Data about breast cancer risk factors were collected. We evaluated correlation and ORs using conditional logistic regression analysis for each case group versus the control group. We also evaluated those factors in three further subgroups: luminal (HR+, HER2-), HER2-overexpressing (HER2+, HR-), and triple-negative (TN) patients. Results: Long duration of breastfeeding of ≥12 months (OR = 4.64, 95% CI 2.97-7.26), body mass index ≤25 (OR = 2.48, 95% CI 1.71-3.58), and use of oral contraceptives (OR = 2.48, 95% CI 1.62-3.84) were the most significant risk factors in favor of IBC compared to non-IBC. There was no impact of contraceptives use in the luminal subgroup and no impact of long duration of breastfeeding in the TN subgroup. The role of socioeconomic and educational levels was unclear. Age at menarche, age at first pregnancy, and age at menopause were nonsignificant risk factors of IBC. Conclusion: Reproductive risk factors were distinct in IBC patients reflecting the clinical entity of IBC.