Article Text

Download PDFPDF
Risk of developing ovarian cancer among women with ovarian endometrioma: a cohort study in Shizuoka, Japan
  1. H. Kobayashi*,
  2. K. Sumimoto,
  3. N. Moniwa,
  4. M. Imai,
  5. K. Takakura,
  6. T. Kuromaki,
  7. E. Morioka,
  8. K. Arisawa and
  9. T. Terao
  1. * Department of Obstetrics and Gynecology, Nara Medical University, Kashihara, Nara, Japan;
  2. Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan;
  3. Shizuoka Cancer Registry, Shizuoka, Japan
  1. Address correspondence and reprint requests to: Hiroshi Kobayashi, MD, PhD, Department of Obstetrics and Gynecology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. Email: hirokoba{at}


Although some studies have indicated that endometriosis may increase the risk of developing ovarian cancer, there are no data from epidemiologic studies in Japan. We prospectively analyzed all cases of ovarian endometrioma enrolled in the prefecture-wide Shizuoka Cohort Study on Endometriosis and Ovarian Cancer Programme, which was initiated in 1985. To evaluate the risk of ovarian cancer by time periods subsequent to ovarian endometrioma diagnosis, a cohort of 6,398 women with a clinically documented ovarian endometrioma in Shizuoka between 1985 and 1995 was identified from the Shizuoka Cancer Registry (SCR), with follow-up through 2002. Ovarian cancer incidence among cohort members was ascertained by linkage to the SCR using a unique person-identification number. Standardized incidence ratios (SIR) and their 95% confidence intervals (CI) were computed by a use of prefecture-wide rates of ovarian cancer, adjusted for age and calendar year. During follow-up of up to 17 years of the ovarian endometrioma cohort, 46 incident ovarian cancers were identified, yielding that the ovarian cancer risk was elevated significantly among patients with ovarian endometrioma (SIR = 8.95, 95% CI = 4.12–15.3). The SIR did not increase with increasing follow-up duration. The risk increased with increasing age at ovarian endometrioma diagnosis, with a SIR equal to 13.2 (95% CI = 6.90–20.9) in women above 50 years of age. Our findings for the first time support the hypothesis that ovarian endometrioma increases the subsequent risk of developing ovarian cancer in Shizuoka, Japan

  • cancer registration
  • endometrioma
  • endometriosis
  • ovarian cancer
  • prospective study

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.