Abstract PS3-02-18: Association of epidemiological and reproductive factors with risk of hormone receptor-positive/negative breast cancer: a case-control study in Beijing, China (CABC011)

Abstract Background: The reason of rapidly increasing of breast cancer (BC) incidence in China has invested in recent years. However, the pathogenesis of BC, especially hormone receptor-positive/negative (HR+/−) BC among the Chinese population, remains unclear. Methods: This was a case-control study conducted in Beijing, China. BC patients and healthy women were enrolled as cases and controls, respectively. Information on demographic factors [(age, body mass index (BMI), education level, family history of cancer)] and reproductive factors (menopausal status, age at menarche, number of pregnancies, number of children, and weather performed breast feeding) were collected using a questionnaire of 28 items. We also collected data on the patients' estrogen receptor (ER) and progesterone receptor (PR) statuses from their medical records. Logistic regression were used to estimate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for the risk factors of interest. Results: We analyzed 471 BC patients and 473 healthy controls. ER and PR expression data were available for 439 BC patients; 355 (75.4%) had HR+ (ER+ and/or PR+) BC, while 84 (17.8%) had HR− (ER− and PR−) BC. Multiple logistic regression analysis indicated that higher education level (OR: 0.619; 95% CI: 0.513∼0.747; P < 0.001), was a protective factor against in all cohort both in HR+ and HR- BC; but in HR+ group showed that full pregnancy (OR: 0.622, 95% CI: 0.425∼0.911, P = 0.015), bearing more children (OR: 0.622, 95% CI: 0.425∼0.911, P= 0.013), less abortion and miscarry (OR: 1.358, 95% CI:1.114 ∼1.655, P = 0.002); took longer period of breast feeding (OR: 0.798, 95% CI: 0.691∼0.921, P = 0.002) , and without family history of BC (OR:9.691, 95% CI: 2.088∼44.983, P = 0.004) were protective factors against HR+ BC; while family history of BC in first degree relatives (OR: 3.076; 95% CI: 0.988∼9.484; P = 0.05) was a risk factor for HR- BC. Conclusions: Higher education level protected against BC, while a family history of BC was a risk factor for BC. Reproductive factors play a more significant role in affecting HR+ BC risk; while genetic factors like family history of BC in first degree relatives are more relevant in the development of HR− BC. Citation Format: H. Li, Y. Lei, F. Zhao, H. Liao, Y. Zhang, Y. Liu, R. Zhang, H. Zhao, R. Ran, H. Chen, Q. Zhan. Association of epidemiological and reproductive factors with risk of hormone receptor-positive/negative breast cancer: a case-control study in Beijing, China (CABC011) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-02-18.