1698P - Do the Well-Known Risk Factors of Breast Cancer Have the Same Impact on Development of Molecular Subtypes?

Abstract

ABSTRACT Background Altough clinical differences between breast cancer (BC) subtypes have been well-described, etiologic heterogeneity have not been fully studied. The aim of this study was to assess the associations between risk factors and molecular subtypes of BC. Methods 1884 invasive BC cases were retrospectively analyzed. The odds ratios (OR) and 95% confidence intervals (CI) were estimated using multiple logistic regression analysis. Results 1249 patients had luminal A, 234 had luminal B, 169 had HER-2 overexpressing and 232 had triple negative BC. The age of ≥40 years was found to be a risk factor for luminal A (OR 1.41 95% CI 1.15-1.74; p = 0.001) and HER-2 overexpressing subtype (OR:1.51, 95% CI:1.01-2.25; p = 0.04). Women who were nulliparous (OR 1.48, 95% CI 1,03-2,13; p = 0.03) or who had their first full-term pregnancy ≥30 years (OR 1.25 95% CI 0.83-1.88; p = 0.04) were at increased risk of luminal BC, whereas women with >2 children had a decreased risk (OR 0.68, 95% CI 0.47-0.97; p = 0.03). Breast-feeding was a protective factor for luminal BC (OR 0.74, 95% CI 0.53-1.04; p = 0.04). We found increased risks for postmenopausal women with HER-2 overexpressing (OR 2.20, 95% CI 0.93-5.17; p = 0.04) and luminal A (OR 1.87, 95% CI 0.93-3.90, p = 0.02) BC, who used hormone replacement therapy for ≥5 years. Overweight and obesity increased the risk of triple negative BC (OR 1.89 95% CI 1.06-3.37; p = 0.04 and OR 1.90 95% CI 1.00-3.61; p = 0.03), on the contrary, decreased the risk of luminal BC (OR 0.63 95% CI 0.43-0.95; p = 0.02 and OR 0.50 95% CI 0.32-0.76; p = 0.002, respectively) in premenopausal women. There were no significant differences between risk of BC subtypes and early menarche, late menopause, family history, postmenopausal obesity, oral contraseptive use, smoking, in vitro fertilization and blood groups. Conclusions Reproductive and hormonal characteristics were associated with luminal BC. Obesity and overweight increased the risk of triple negative subtype, particularly in premenopausal women. Older age and use of hormone replacement therapy were related to the risk of HER-2 overexpressing BC. Our data suggest a significant heterogeneity in association of traditional BC risk factors and tumor subtypes. Disclosure All authors have declared no conflicts of interest.