Epidemiological risk factors associated with inflammatory breast cancer subtypes

Background: In this single-institution case–control study, we identified risk factors associated with inflammatory breast cancer (IBC) subtypes based on staining of estrogen receptor (ER), progesterone receptor (PR) and expression of human epidermal growth factor 2 (HER2neu) to determine distinct etiologic pathways. Methods: We identified 224 women with IBC and 396 cancer-free women seen at the MD Anderson Cancer Center. Multinomial logistic regression was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs) for associations between breast cancer risk factors and the IBC tumor subtypes: luminal (ER+ and/or PR+/HER2neu−), HER2neu+ (any ER and PR, HER2neu+), and triple-negative (ER−/PR−/HER2neu−). Results: In multivariable analysis, compared with women age ≥26 at first pregnancy, women age <26 had a higher risk of triple-negative IBC (OR 3.32, 95% CI 1.37–8.05). Women with a history of breast-feeding had a lower risk of triple-negative (OR 0.30; 95% CI 0.15–0.62) and luminal IBC (OR 0.35, 95% CI 0.18–0.68). A history of smoking was associated with an increased risk of luminal IBC (OR 2.37; 95% CI 1.24–4.52). Compared with normal-weight women, those who were overweight or obese (body mass index ≥25 kg/m²) had a higher risk of all three tumor subtypes (p < 0.01 for all subtypes). Conclusion: Overweight or obese status is important modifiable risk factor for IBC of any subtype. Modifiable risk factors, age at first pregnancy (≥26), breast-feeding, and smoking may be associated with specific IBC subtypes. These results highlight the importance of evaluating epidemiologic risk factors for IBC for the identification of subtype-specific prevention strategies.