The impact of endogenous estrogen exposures on the characteristics and outcomes of estrogen receptor positive, early breast cancer.

BACKGROUND

Menstrual and parity history might impact the risk for 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 estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2) negative, early breast cancer whose tumors were sent to OncotypeDX analysis. The prespecified subgroups were investigated: age of menarche (< 12 vs. ≥ 12 years), number of deliveries (0 vs. ≥ 1 childbirth and ≥ 5 childbirth vs. other), age of first delivery (≥ 30 years vs. younger age) and postmenopausal compared to premenopausal. The impact of age of menopause was also assessed categorically, using early (< 45 years) and late age of menopause (> 55 years). Differences in tumor characteristics were evaluated using T-test or Mann Whitney for continuous variables or Fisher's exact test for categorical variables. Outcomes were assessed by Kaplan-Meier survival analysis, with the log-rank test.

RESULTS

A total of 620 women were included. After median follow-up of 10.4 years, early menopause was associated with significantly worse disease-free survival (HR = 2.26, p = 0.004) and overall-survival (HR = 2.60, p = 0.004), and multiparity was associated with significant worse disease-free survival (HR = 2.16, p = 0.026). These differences remain significant in multivariate analyses. Post-menopausal women were more likely to have stronger ER intensity (p = 0.002) but progesterone receptor (PR) positivity was less frequent (p = 0.009(. Early age of menarche was associated with PR positivity (p = 0.039). No other associations were found between the evaluated subgroups and tumor characteristics.

CONCLUSIONS

The impact of endogenous estrogen exposure had little effect on breast cancer characteristics of early stage, luminal disease. Early menopause and multiparity were associated with worse outcome.