Abstract P6-12-04: Risk factors for inflammatory breast cancer

Abstract

Background: The 5-year survival rates for inflammatory breast cancer (IBC) are significantly lower than non-IBC, highlighting the importance of cancer prevention in IBC. We investigated the risk factors for IBC subtypes based on estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor 2 (HER2neu) status to determine distinct etiological pathways. The Morgan Welch Inflammatory Breast Cancer Research Program and Clinic at University of Texas MD Anderson Cancer Center (UTMDACC) treats the largest number of IBC patients in a single center. The center maintains a prospective, comprehensive epidemiology registry, through which we were able to conduct the largest single center case-control study on IBC. Methods: We identified 246 patients diagnosed with IBC using strict consensus criteria and 397 cancer free patients seen at the UTMDACC Dan L. Duncan Cancer prevention clinic. We used logistic regression to estimate the odds ratios (OR) and 95% confidence intervals (CI) for the associations between breast cancer reproductive and lifestyle risk factors and IBC tumor subtypes. The tumor subtypes of IBC patients were classified as ER-positive (ER+/PR+/Her2neu-), Her2neu-positive (Her2neu+) and triple negative (ER-/PR-/Her2neu-). Results: In age-adjusted univariate analysis, body mass index (BMI), history of smoking, number of children, age at first pregnancy, breastfeeding, menopausal status, and first degree family history of breast cancer were statistically significant associated with risk of IBC (p<0.05). In multivariable analysis of IBC tumor subtypes, compared to cancer free controls, patients with triple negative (OR = 3.73, 95% CI = 1.52 – 9.13) and Her2neu-positive (OR = 19.27, CI = 4.14 – 89.62) tumors were significantly more likely to have ≥ 2 vs 0-1 children. Patients with triple negative (OR = 0.19, 95% CI = 0.09 – 0.45) and ER-positive (OR = 0.42, CI = 0.19 – 0.88) tumors were significantly less likely to have a history of breastfeeding. Patients with ER-positive (OR = 5.02, CI = 2.29 – 10.99) tumors were also significantly more likely to have a history of smoking. Patients with triple negative (OR = 6.07, CI = 2.62 – 17.07), ER-positive (OR = 7.22, CI = 2.94 – 17.78) and Her2neu-positive (OR = 12.81, CI = 4.59 – 35.78) were more likely to be overweight or obese (BMI ≥ 25kg/m2). Conclusion: The associations identified suggest that overweight or obese status is an important modifiable risk factor for all IBC subtypes. Triple negative IBC share similar risk factors as non-IBC triple negative tumors with increasing number of children and lack of breastfeeding associated with increased risk. Interestingly lack of breastfeeding was also associated with ER-positive IBC tumors, and Her2neu-positive IBC tumors were associated with increasing number of children; two associations that have not been previously reported. Impact: These results highlight the importance of evaluating epidemiologic risk factors of IBC, which could lead to the identification of subtype specific prevention strategies. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-12-04.