Abstract 3465: Association with total reproductive year and the risk of biliary tract cancer in women
Authors: Maeng Chi Hoon , Han Kyungdo , Park Joo-Hyun , Hong Jung Yong 
Published: March 2024

Abstract
Background: Many studies have reported that female reproductive factors, such as parity, age at menarche or menopause, breastfeeding, or age at first birth, were associated with or not associated with the development of biliary tract cancer (BTC). Our study was planned to determine whether a long-term rather than transient exposure was associated with the risk of BTC, including total reproductive year, which was defined as the time from menarche to menopause throughout the life cycle.
Methods: This nationwide cohort study included 1,059,533 women with natural menopausal women aged 40-69 years who underwent the periodic health check-up provided by the Korean National Health Insurance System in 2009. The median follow-up period was 9.3 years. Cox proportional hazard regression analysis was performed to estimate the risk of BTC based on the female reproductive factors.
Results: During the 9,867,152 person-years of follow-up, 4,198 patients (0.4%) were newly diagnosed with BTC. The incidence of BTC was significantly increased in subjects younger than 40 years at menopause compared with those aged 40 years or older (HR 1.341, 95% CI, 1.095-1.642). This trend was consistent even when menopause age was subdivided into 5-year intervals (&lt;40 vs. 40−44, 45−49, 50-54, and ≥ 55 years) for those aged 40 years or older. When compared by categorization into four quartiles, the incidence of BTC tended to be numerically lower than that of the bottom 25% with the lowest age of menopause (designated as Q1 reference group). Compared to those with total reproductive year of 30 years or more, the incidence of BTC increased significantly in the group with less than 30 years of total reproductive year (HR 1.106, 95% CI, 1.014-1.206). This tendency was significantly reproduced in comparison by categorizing the entire group into quartiles. Compared to the lower 25% group (designated as Q1 reference group), the risk of BTC showed a significant linear inverse correlation with the longer total reproductive year. Q1 group has significantly higher incidence of BTC compared to the other groups (p &lt; 0.001). This trend was repeated in various subgroup analysis.
Conclusions: In conclusion, this study demonstrated that women under the age of 40 at menopause had an increased risk of BTC compared to those over 40 years of age. Similarly, a longer period of total reproductive year was associated with a lower risk of BTC, suggesting a protective female hormonal effect on BTC. Total reproductive year may be more reliable indicator in that it reflects the actual lifetime exposure to female hormones.
Citation Format: Chi Hoon Maeng, Kyungdo Han, Joo-Hyun Park, Jung Yong Hong. Association with total reproductive year and the risk of biliary tract cancer in women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3465.