interaction of estrogen and progesterone receptors, and human epithelial receptor 2, with breast cancer risk factors: a multi-center case-only study in iran

The etiology of breast cancer and our understanding on the carcinogenicity of different risk factors is impotant for control programms.
We investigated the expression of estrogen and progesterone receptors (ER, PR), and human epithelial receptor 2 (HER2) overexpression and its associations, with environmental risk factors among breast cancer patients.
We classified the patients into four groups including; triple negative (ER–/PR–/HER2-), HER2-overexpression (ER–/PR–/HER2), luminal A (ER and/or PRﱱ) and luminal B (ER and/or PRﱱᇛ). We used a case-only design and multinomial logistic regression analyses.
In premenopausal patients, those with high BMI had lower prevalence of luminal B tumors compared to luminal A groups (OR= 0.42, 95% CI= 0.23 to 0.74). However, in the postmenopausal groups, prevalence of the luminal B tumors was less than luminal A tumors oral contraceptive pill (OCP) users (OR= 0.64, 95% CI= 0.42 to 0.98). In addition, among those who had an older age at menarche had a higher risk of ER2-overexpression tumors compared to luminal A tumors (OR= 2.82, 95% CI= 1.29-6.19).
Expression of HER2, ER, and PR, among breast cancer patients seems to be associated with OCP use, BMI, age at menarche and age at first pregnancy.