Impact of levonorgestrel-releasing intrauterine system use on the cancer risk of the ovary and fallopian tube

Background: Levonorgestrel-releasing intrauterine system (LNG-IUS) is used for contraception and heavy menstrual bleeding. A long-term hormone therapy can modify the risk of gynecologic cancers. Little is known about the impact of LNG-IUS use on the risk for invasive and borderline ovarian tumor subtypes or for primary fallopian tube carcinoma. We examined the associations of LNG-IUS use with these tumors.Material and methods: We identified from the national Medical Reimbursement Registry of Finland the women aged 30-49 years who had used LNG-IUS for menorrhagia in 1994-2007, and from the Finnish Cancer Registry ovarian cancers and primary fallopian tube carcinomas diagnosed before the age of 55 and by the end of 2013.Results: A total of 77 invasive ovarian cancers and seven primary fallopian tube carcinoma cases were diagnosed in a cohort of 93 843 LNG-IUS users during the follow-up of 1 083 126 women-years. The LNG-IUS users had decreased risk for both invasive ovarian cancer [standardized incidence ratio (SIR) 0.59, 95% confidence interval (CI) 0.47-0.73] and for borderline ovarian tumors (SIR 0.76, 95% CI 0.57-0.99) as compared to the background population. The risk of primary fallopian tube carcinoma was not increased (SIR 1.22, 95% CI 0.49-2.50). Decreased risks for mucinous (SIR 0.49, 95% CI 0.24-0.87), endometrioid (SIR 0.55, 95% CI 0.28-0.98), and serous ovarian carcinomas (SIR 0.75, 95% CI 0.55-0.99) were seen in LNG-IUS users.Conclusions: LNG-IUS use associated with decreased risk for both invasive and borderline ovarian tumors. The incidence of primary fallopian tube carcinoma did not significantly differ between LNG-IUS users and the background population.