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Methods: A retrospective cohort study emulated a target trial, using Taiwan’s National Health Insurance claims linked to the cancer registry. Results: Among 23,062 tamoxifen users and 3,000 nonusers, uterine diseases and specific malignancies were more frequent with tamoxifen. Conclusion: In premenopausal women in Taiwan, adjuvant tamoxifen was associated with increased risk of uterine diseases, including endometrial cancer.",{"@graph":69,"@context":127},[70,84,106],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/tamoxifen-use-and-risk-of-uterine-diseases-in-young-women-with-breast-cancer/355479/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/tamoxifen-use-and-risk-of-uterine-diseases-in-young-women-with-breast-cancer/355479.png","ImageObject",300,407,{"name":92,"@type":93},"Aria Callaghan","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-27","2026-09-22",true,{"@type":102,"interactionType":103,"userInteractionCount":105},"InteractionCounter",{"@type":104},"ViewAction",11,{"@type":107,"mainEntity":108},"FAQPage",[109,115,119,123],{"name":110,"@type":111,"acceptedAnswer":112},"What was the study objective regarding tamoxifen and uterine disease risk?","Question",{"text":113,"@type":114},"To investigate whether tamoxifen treatment is associated with the risk of developing uterine diseases in premenopausal women with breast cancer.","Answer",{"name":116,"@type":111,"acceptedAnswer":117},"How were participants selected and what key exclusions were applied?",{"text":118,"@type":114},"Women aged 20–50 with estrogen receptor–positive breast cancer treated between 2010 and 2019 were identified from linked Taiwan health data; those with hysterectomy, neoadjuvant therapy, and postmenopausal status/uterine diseases at diagnosis were excluded.",{"name":120,"@type":111,"acceptedAnswer":121},"What were the main results for uterine diseases and endometrial cancer?",{"text":122,"@type":114},"During follow-up, uterine diseases occurred more often in tamoxifen users than nonusers. In intention-to-treat analysis, hazard ratios were higher for endometrial polyps and hyperplasia, and endometrial cancer also increased.",{"name":124,"@type":111,"acceptedAnswer":125},"What conclusion does the study draw for premenopausal women in Taiwan?",{"text":126,"@type":114},"Adjuvant tamoxifen in premenopausal breast cancer patients was associated with increased risk of uterine diseases, including endometrial cancer, supporting the need for monitoring in this age group.","https://schema.org",{"og:url":83,"og:type":129,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":131,"canonical":83},"index,follow",{"doc_id":133,"site_id":62},355479,1790176610,{"code":4,"msg":5,"data":136},{"doc_id":133,"user_id":137,"nickname":92,"user_avatar":138,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":139,"file_id":140,"file_url":141,"file_type":142,"file_size":143,"view_count":105,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":52,"language":144,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":145,"faqs":146,"seo_title":147,"seo_description":67,"update_tm":148,"read_time":149},962084926284,"https://ap-avatar.wpscdn.com/davatar_29158cc5080c5b710cf443261637dec0","Original Research  \nTamoxifen Use and Risk of Uterine Diseases in Young Women With Breast Cancer  \nYi-Chun Yeh, PhD, Pei-Chun Chen, PhD, Hsin-Ya Huang, MS, and Cherry Yin-Yi Chang, MD, PhD  \nOBJECTIVE: Tamoxifen use has been associated with an increased risk of endometrial cancer in women with breast cancer, but data on premenopausal women in Asia remain limited. We investigated the association between tamoxifen treatment and risk of developing uterine diseases in women of premenopausal age with breast cancer.  \nMETHODS: We conducted a retrospective cohort study using a target trial emulation framework. Women aged 20–50 years who were diagnosed with estrogen receptor–positive breast cancer and had undergone mastectomy or lumpectomy from 2010 to 2019 were identified with Taiwan’s National Health Insurance claims data linked to the cancer registry. Those with a history of hysterectomy, neoadjuvant therapy, and diagnosis of postmenopausal status and uterine diseases were excluded. Tamoxifen use was defined as receipt tamoxifen treatment only as adjuvant hormone treatment within 1 year after surgery. Inverse probability of treatment weighting  \n\n| From the National Centerfor Geriatrics and Welfare Research, National Health Research Institutes, Yunlin, the Big Data Center and the Department of Obstetrics & Gynecology, China Medical University Hospital, and the Department of Medicine, School of Medicine, China Medical University, Taichung, and the Division of Breast Surgery, Changhua Christian Hospital, Changhua, Taiwan.\u003Cbr>Presented in part at the 16th Asian Conference on Pharmacoepidemiology, October 12–14, 2024, Tokyo, Japan.\u003Cbr>The authors are grateful to the Health Data Science Center, China Medical University Hospital, for providing administrative and technical support.\u003Cbr>Each author has confirmed compliance with the journal’s requirements for authorship.\u003Cbr>Corresponding author: Cherry Yin-Yi Chang, MD, PhD, Department of Obstetrics & Gynecology, China Medical University Hospital, Taichung, Taiwan; [changyinyi@hotmail. com](changyinyi@hotmail. com) |\n| --- |\n| Financial Disclosure\u003Cbr>The authors did not report any potential conflicts of interest. |\n\nCopyright © 2026 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American College of Obstetricians & Gynecologists. This is an open access article distributed under the terms of the Creative Commons Attribution- -Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.  \nISSN: 0029-7844/26  \ncontrolled baseline confounding between the tamoxifen treatment and nontreatment groups. Observational analogs of the intention-to-treat and per-protocol effects were estimated with pooled logistic regression models. RESULTS: A total of 23,062 tamoxifen users and 3,000 nonusers were included. During the follow-up period, 3,889 users and 109 nonusers developed uterine diseases, including 106 and 5 cases of endometrial cancer, respectively. In the intention-to-treat analysis, the hazard ratio was 4.15 (95% CI, 2.65–6.50) for endometrial polyps, 5.42 (95% CI, 4.09–7.18) for endometrial hyperplasia, and 2.41 (95% CI, 0.86–6.72) for endometrial cancer. Corresponding estimates from the per-protocol analysis were 4.75 (95% CI, 2.55–8.86), 8.37 (95% CI, 5.24–13.35), and 4.20 (95% CI, 1.20–14.63), respectively. The risk of all uterine diseases increased with longer duration of tamoxifen use.  \nCONCLUSION: Among women of premenopausal age with breast cancer in Taiwan, tamoxifen as adjuvant hormone therapy was associated with increased risk of uterine diseases, including endometrial cancer. These findings highlight the importance of monitoring uterine diseases among tamoxifen users in this age range.(Obstet Gynecol 2026;147:725–34)  \nDOI: 10. 1097/AOG.0000000000006238  \nBreast cancer is the most common ","cbCaisEvTmZ3iwEM","https://ap.wps.com/l/cbCaisEvTmZ3iwEM","pdf",1622333,"English","# Objective\n# Methods\n# Results\n# Conclusion\n## Background on Breast Cancer and Endocrine Therapy","[{\"question\":\"What was the study objective regarding tamoxifen and uterine disease risk?\",\"answer\":\"To investigate whether tamoxifen treatment is associated with the risk of developing uterine diseases in premenopausal women with breast cancer.\"},{\"question\":\"How were participants selected and what key exclusions were applied?\",\"answer\":\"Women aged 20–50 with estrogen receptor–positive breast cancer treated between 2010 and 2019 were identified from linked Taiwan health data; those with hysterectomy, neoadjuvant therapy, and postmenopausal status/uterine diseases at diagnosis were excluded.\"},{\"question\":\"What were the main results for uterine diseases and endometrial cancer?\",\"answer\":\"During follow-up, uterine diseases occurred more often in tamoxifen users than nonusers. In intention-to-treat analysis, hazard ratios were higher for endometrial polyps and hyperplasia, and endometrial cancer also increased.\"},{\"question\":\"What conclusion does the study draw for premenopausal women in Taiwan?\",\"answer\":\"Adjuvant tamoxifen in premenopausal breast cancer patients was associated with increased risk of uterine diseases, including endometrial cancer, supporting the need for monitoring in this age group.\"}]","Tamoxifen Use and Risk of Uterine Diseases in Young Women With Breast Cancer | PDF",1790119299,25]