title: Tamoxifen use reduces the risk of osteoporotic fractures in women with breast cancer in Asia: a nationwide population-based cohort study.
abstract: OBJECTIVE
  Bone mineral density changes with tamoxifen treatment have been reported in pre- and post-menopausal women with breast cancer. However, there remains controversy as to whether tamoxifen significantly reduces fracture rates in different age groups. Breast cancer occurs at 10-20 years younger in Asian women compared with Western women. Therefore we conducted this population-based case-control study to determine whether or not tamoxifen use is associated with osteoporotic fractures.
  
  
  METHODS
  We selected 75488 women with breast cancer with no prior history of fractures from the Longitudinal Health Insurance Database for Catastrophic Illness Patients in 2000-2011. They were followed from the date of the diagnosis of breast cancer to the date a hip, vertebral or wrist fracture occurred. Because the use of tamoxifen was a time-dependent variable, we used a Cox proportional hazard model with time-dependent exposure covariates to estimate the risk of a fracture.
  
  
  RESULTS
  There were 50257 and 25231 women with breast cancer who did and did not receive tamoxifen treatment, respectively. The tamoxifen users had lower risks for overall fractures with hazard ratios (HRs) of 0.52 and 0.59 in the crude and adjusted models (95 % CI = 0.45-0.61 and 0.51-0.69), respectively. They also had lower risks for hip (HR = 0.55, 95 % CI = 0.45-0.67) and vertebral (HR = 0.64, 95 % CI = 0.50-0.82) fractures in the adjusted model. The risk of fractures decreased with an increasing dosage of tamoxifen. Regardless of the age group, the tamoxifen users had a lower risk of fractures than the non-users.
  
  
  CONCLUSIONS
  In this Asian population-based case-control study, tamoxifen use was associated with a reduction in osteoporotic fractures, especially in hip fractures.
authors.affiliation: Graduate Institute of Clinical Medicine, China Medical University, #91 Hsueh-Shih Road, Taichung, 404, Taiwan. tzenghueyen@gmail.com.|Division of Hematology/Oncology, Taichung Veterans General Hospital, Taichung, Taiwan. tzenghueyen@gmail.com.|School of Medicine, China Medical University, Taichung, Taiwan. tzenghueyen@gmail.com.
authors.forename: Huey-En
authors.initials: HE
authors.lastname: Tzeng
authors.affiliation: Management Office for Health Data, China Medical University Hospital, Taichung, Taiwan. a17776@mail.cmuh.org.tw.
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Muo
authors.affiliation: Department of Orthopedics, China Medical University Hospital, Taichung, Taiwan. bonekid1@gmail.com.|School of Chinese Medicine, China Medical University, Taichung, Taiwan. bonekid1@gmail.com.
authors.forename: Hsien-Te
authors.initials: HT
authors.lastname: Chen
authors.affiliation: Division of Hematology/Oncology, Taichung Veterans General Hospital, Taichung, Taiwan. kevinhwl@gmail.com.
authors.forename: Wen-Li
authors.initials: WL
authors.lastname: Hwang
authors.affiliation: School of Medicine, China Medical University, Taichung, Taiwan. D4749@mail.cmuh.org.tw.|Department of Orthopedics, China Medical University Hospital, Taichung, Taiwan. D4749@mail.cmuh.org.tw.
authors.forename: Horng-Chang
authors.initials: HC
authors.lastname: Hsu
authors.affiliation: Graduate Institute of Clinical Medicine, China Medical University, #91 Hsueh-Shih Road, Taichung, 404, Taiwan. ritsai8615@gmail.com.|School of Medicine, China Medical University, Taichung, Taiwan. ritsai8615@gmail.com.|Department of Orthopedics, China Medical University Hospital, Taichung, Taiwan. ritsai8615@gmail.com.
authors.forename: Chun-Hao
authors.initials: CH
authors.lastname: Tsai
mesh_terms: D000367:Age Factors; D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D006620:Hip Fractures / Q000453:epidemiology / Q000517:prevention & control; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D058866:Osteoporotic Fractures / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D016016:Proportional Hazards Models; D065840:Protective Factors; D012307:Risk Factors; D016103:Spinal Fractures / Q000453:epidemiology / Q000517:prevention & control; D013624:Taiwan / Q000453:epidemiology; D013629:Tamoxifen / Q000627:therapeutic use*; D013997:Time Factors; D014954:Wrist Injuries / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D018931:Antineoplastic Agents, Hormonal; D050071:Bone Density Conservation Agents; D013629:Tamoxifen