| Summary: | 碩士 === 國立臺灣師範大學 === 健康促進與衛生教育學系 === 106 === Importance: Although data from a number of studies over the last 20 years have discovered association between tamoxifen and endometrial cancer among breast cancer women, there is still rare study discussing this issue taking the mortality, other confounding factors and the dynamic use of drug into account.
Objective: The aim of this study is to investigate the association between tamoxifen and endometrial cancer among breast cancer women.
Design: This is a population-based retrospective cohort study. The index date is set as the first prescription of tamoxifen + 180 days.
Setting: We conduct this study by using the National Health Insurance Database (NHID) and Serious Disabling Diseases (SDD) database in Taiwan.
Participants: Female patients with newly-diagnosis of breast cancer during Jan 1, 2000 to Dec 31, 2012 are recruited from registry for SDD in this study (n=99,895). Using exact matching, control (n=20,875) is matched per case by newly-diagnosis year of breast cancer, year of birth, comorbidity and socioeconomic index.
Exposure: Female patients with newly-diagnosis of breast cancer and use tamoxifen during Jan 1, 2000 to Dec 31, 2013 include in this study. Tamoxifen defines as Anatomical Therapeutic Chemical (ATC) by WHO is L02BA01, and its Define Daily Dose (DDD) is 20mg
Main Outcome Measure: Endometrial cancer classify according to the ICD-9 code is 182.xx from Registry for SDD.
Statistics analysis: Chi-square or t tests use to examine differences of women with newly-diagnosis breast cancer in demographic and characteristics between tamoxifen exposure cases and controls. Hysterectomy、other cancer (malignant) and death are taken as competing risks. Using competing risk adjusted Cox regression model (model 1) and Time-dependent competing risk adjusted Cox regression model (model 2), we will evaluate the association between tamoxifen and endometrial cancer among breast cancer patients in Taiwan.
Result：This study in model 1 showed that breast cancer patients in Taiwan use less or over 238 DDD tamoxifen per year during follow-up, the risk in endometrial cancer was higher than that of non-users (HR:2.49,95%CI:1.23-
5.03,p=0.011；HR: 16.46, 95%CI: 8.46-31.99, p<0.001). Over 50 years old users by age stratification, the risk was higher than that of non-users (HR: 6.3, 95%CI: 2.91-13.65, p<0.001). The risk of endometrial cancer in patients who use tamoxifen and aromatase inhibitors was higher than those non-users (HR: 4.06, 95%CI: 2.37-6.96, p<0.001), especially for over 50 years old users. (HR: 6.76, 95%CI: 3.09-14.79, p<0.001); however, using aromatase inhibitors alone had no correlation with the risk of endometrial cancer.
In model 2, breast cancer patients in Taiwan use over 336 DDD tamoxifen per year during follow-up, the risk in endometrial cancer was higher than that of non-users (HR:3.12,95%CI:1.65-5.93,p=0.001). With an increase of each additional 100 DDD of tamoxifen during 180 days prior to index date, the risk of endometrial cancer increased by 16%(HR:1.16,95%CI:
1.01-1.34,p=0.040). Over 50 years old users by age stratification, the risk was higher than that of non-users (HR: 2.55, 95%CI: 1.41-4.61, p=0.002). The risk was also higher with using of tamoxifen and aromatase inhibitors than with non-users in endometrial cancer (HR: 7.3, 95%CI: 4.23-12.59, p<0.001). The risk in 20-49 years and 50 years of age with using of tamoxifen and aromatase inhibitors was higher than in non-users(HR:5.38,95%CI:2.33-12.44,p<0.001；HR: 11,95%CI:4.97-24.53,p<0.001); however, the use of aromatase inhibitors alone was not association with the risk of endometrial cancer among breast cancer patients.
Conclusion：This was a population-based retrospective cohort study from the National Health Insurance Database. In this study, we observed the association between tamoxifen and endometrial cancer among breast cancer patients in Taiwan. Taking the mortality, other confounding factors and the dynamic use of drug into account, we designed the competition risk model (model 1) and time-dependent analysis- competition risk model (model 2). Our data suggested that the use of tamoxifen in breast cancer patients among Taiwan increased the risk of endometrial cancer, especially for those who were over 50 years of age. Furthermore, using tamoxifen and aromatase inhibitors over 50 years of age increased the risk of endometrial cancer; however, the use of aromatase inhibitors alone was not association with the risk, which may come from the effect of tamoxifen. Finally, to analyze two models in this study, we found the risk in endometrial cancer among breast cancer patients who use tamoxifen was association with dosage. Besides, the initial dose of tamoxifen during 180 days prior to index date was also association with the risk of endometrial cancer.
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