Abstract 1305: Assisted reproductive technology and the risk of female sex hormone-related cancers.

Abstract Background: Whether assisted reproductive technology (ART) treatment is associated with the risk of female sex hormone-related cancers is inconclusive. Methods: This study leveraged the national data from Taiwan to assemble the largest ART cohorts. The primary objective was to assess the associations of ART with the risk of breast, ovarian, and endometrial cancers. The secondary objectives included the associations of ART cycle numbers, age at the first ART treatment, and history of childbirth with the risk of these cancers. Cox proportional hazards regression models were used for data analysis. Results: The cohorts with or without ART exposure for breast, ovarian, or endometrial cancer risk assessment included 104,486, 104,936, or 104,913 subjects, respectively. The results showed that ART was independently associated with an increased risk of breast (HR, 1.11; 95% CI, 1.04 to 1.19) and ovarian (HR, 1.38; 95% CI, 1.13 to 1.69) cancers, but not endometrial cancer. The data also revealed a dose-response relationship between ART cycle numbers (2 versus 1) and the risk of breast (HR, 1.13; 95% CI, 1.03 to 1.25) and ovarian (HR, 1.45; 95% CI, 1.10 to 1.90) cancers. No statistically significant associations between age at the first ART and the risk of these cancer types were observed. Subgroup analyses suggested protective effects of childbirth against ovarian and endometrial cancers. Conclusions: This study demonstrated a statistically significant increase in the risk of breast and ovarian cancers among women with ART treatment. The results suggested that regular checkups for cancer should be considered once ART exposure is established. Citation Format: Emily Pei-Ying Lin, Ching-Heng Lin, Chih-Yuan Hsu, Wei-Szu Lin, Jui-Chun Chang, Bo-Tsang Huang, Hong-Nerng Ho, Yu Shyr. Assisted reproductive technology and the risk of female sex hormone-related cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1305.