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Increased Association Between Endometriosis and Endometrial Cancer: A Nationwide Population-Based Retrospective Cohort Study
  1. Hann-Chin Yu, MD*,
  2. Chun-Yi Lin, PhD,
  3. Wei-Chiao Chang, PhD,
  4. Biing-Jiun Shen, PhD§,
  5. Wei-Pin Chang, PhD and
  6. Chi-Mu Chuang, MD, PhD,
  1. *Department of Obstetrics and Gynecology, Hsinchu Branch, Taipei Veterans General Hospital;
  2. Department of Healthcare Management, Yuanpei University, Hsinchu;
  3. Department of Clinical Pharmacy, School of Pharmacy, Taipei Medical University, Taipei, Taiwan;
  4. §Division of Psychology, Nanyang Technological University, Singapore;
  5. Section of Gynecologic Oncology, Department of Obstetrics and Gynecology, Taipei Veterans General Hospital; and
  6. Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
  1. Address correspondence and reprint requests to Chi-Mu Chuang, MD, PhD, No. 155, Sec. 2, Linong Street, Taipei, 112 Taiwan. E-mail:


Objective Association between endometriosis and ovarian cancer has been well established. Nonetheless, endometriosis may also be associated with endometrial cancer because of shared etiological mechanisms of both estrogen stimulation and chronic inflammation; however, the association between these 2 disorders has rarely been investigated.

Methods The National Health Insurance Research Databases in Taiwan were retrieved and analyzed. The case cohort consisted of patients with a diagnosis of endometriosis between January 1997 and December 2000 (N = 15,488). For the construction of control cohort, 8 age- and sex-matched control patients for every patient in the case cohort were selected using a random sampling method (n = 123,904). All subjects were tracked for 10 years from the date of entry to identify whether they had developed endometrial cancer. The Cox proportional hazards regression model was used to evaluate 10-year event occurrence of endometrial cancer.

Results During the 10-year follow-up period, 392 participants developed endometrial cancer, with 104 (0.7%) distributed in the case cohort and 288 (0.2%) in the control cohort. Multivariable Cox regression modeling demonstrates a higher risk for developing endometrial cancer in the case cohort than in the control cohort (adjusted hazard ratio [aHR], 2.83; 95% confidence interval [CI], 1.495.35; P < 0.01). Age at diagnosis of endometriosis shows a moderator effect: when 40 years or younger, the risk for developing endometrial cancer was comparable between the case cohort and the control cohort (aHR, 1.42; 95% CI, 0.55–3.70; P = 0.226), whereas when older than 40 years, the risk for developing endometrial cancer was higher in the former group than in the latter group (aHR, 7.08; 95% CI, 2.33–21.55; P = 0.007).

Conclusions Patients diagnosed with endometriosis may harbor an increased risk for developing endometrial cancer in their later life. Closer monitoring is advised for this patient population.

  • Endometrial cancer
  • Endometriosis
  • Population-based cohort study

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  • Supported by the National Science Council, Taiwan (Grants No. NSC 101-2623-E-010-001-NU).

  • The authors declare no conflicts of interest.

  • This study is based in part on data from the NHIRDs provided by the Bureau of NHI, Department of Health, Taiwan, and managed by the NHRI. The interpretations and conclusions reported herein do not represent those of the Bureau of NHI, Department of Health, or the NHRI.

  • This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License, 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.