The impact of endogenous estrogen exposure on the characteristics of estrogen receptor (ER) positive, early-stage breast cancer (EBC).

Abstract

e12605 Background: Menstrual and parity history might impact the risk for ER positive breast cancer. Data on the impact of these factors on other tumor characteristics are limited. Methods: A single center retrospective cohort study comprising all women with ER positive, human epidermal growth factor receptor 2 (HER2) negative, EBC whose tumors were sent to OncotypeDX analysis and were treated in our institute between 2005 to 2012. Data on endogenous estrogen exposure were collected including: age of menarche and menopause, number of deliveries and age of first delivery. Subsequently, data on pre-specified clinical and histopathological features were collected including: tumor size, nodal status, ER and progesterone receptor (PR) staining, grade, Oncotype recurrence score (RS), ki67, lymphovascular and perineural invasion. The impact of endogenous estrogen exposure was evaluated by multiple comparisons including: early age of (<12 years) compared to older age of menarche, nulliparity compared to women who had at least one delivery, multiparty (≥5 deliveries) compared to other, late age of first delivery (≥30 years) compared to other and postmenopausal compared to premenopausal. In postmenopausal women the age of menopause was also assessed using early age of menopause (<45 years) and late age of menopause (>55 years). Results: A total of 620 women were included. 79% were postmenopausal, median age of menarche was 13 (range 9-17) and median number of deliveries was three (range 0-14). Post-menopausal women were more likely to have stronger ER intensity (79% vs. 65%, p=0.002) and less likely to have high (≥31) RS (8% vs. 16%, p=0.021), but PR negativity was significantly more frequent (16% vs. 7%, p=0.007. Additionally, early age of menarche was associated with PR positivity (94% vs. 85%, p=0.039).). No other associations were found between endogenous estrogen exposures and tumor characteristics. Conclusions: These findings suggest that premenopausal women with luminal EBC might have more aggressive disease. Large scale studies are needed to elucidate the impact of endogenous estrogen on luminal breast cancer.