الفهرس 
cover English
(1)EpidemiologyOnly 14 pages are availabe for public view
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Abstract
Breast cancer is characterized by its molecular and clinical heterogeneity. The current study focuses on assessing how risk factors relate to molecular subtypes.Patients & methods: A total of 507 female patients with breast cancer who have been followed up at NCI & Nasser institute during the period from July 2012 till February 2013 were included & categorized into 5 molecular subtypes by immunohistochemistry. Case-case odds ratios comparing risk factors across tumor subtypes using the luminal A tumors as the reference groupwere estimated.Results: Three hundred and twenty one patients had luminal A, 73 had luminal B, 66 had Her2-overexpressing, 30 had basal like and 17 had unclassified breast cancers. We observed significant differences in biological subtypes for the distribution of residence (p=<0.001), age at diagnosis (P = 0.016), number of full term births (P =0.028) and history of contraception use (p=0.026). The age of ≤35 years was found to be a risk factor for unclassified tumors (OR: 5.16, 95% CI: 1.68-15.85; P = 0.008 compared with luminal A), similar to Luminal B and HER2 expressing cases (p=0.087 and 0.045 compared with Luminal A respectively).Rural residents were more likely to be unclassified cases (OR: 7.97, 95% CI: 2.53-25.07; P = <0.001 compared with luminal A). Nulliparous women had an increased risk of unclassified tumors (OR: 5.22, 95% CI: 1.53-17.83 p=0.008 compared with Luminal A), while women who had ≥ 2 children were found to be at high risk for Luminal B (OR: 3.241, 95 %CI: 1.48-7.09; P=0.003 compared to Luminal A). Premenopausal patients were associated with increased risk of unclassified breast cancer (OR: 3.43, 95% CI: 1.28-9.24; p=0.015 compared with Luminal A) whereas, no significant difference were found for other subtypes. Patients with history of combined estrogen and progesterone contraception use were associated with a significant increased risk of unclassified tumors (OR: 0.1, 95% CI: 0.02- 0.54; p= 0.004) while no protective association was seen against other biological subtypes. We observed that compared with the predominant luminal A tumors , association with age at menarche, education, age at first full term birth , family history of breast cancer and BMI showed no significant difference with biological subtypes.Conclusion: Results from this study have shown that luminal A and unclassified tumors seem to have distinct sets of risk factors, suggesting etiologic, in addition to clinical, heterogeneity.