A1 Refereed original research article in a scientific journal
Levonorgestrel-releasing intrauterine system and the risk of breast cancer: A nationwide cohort study
Authors: Tuuli Soini, Ritva Hurskainen, Seija Grénman, Johanna Mäenpää, Jorma Paavonen, Heikki Joensuu, Eero Pukkala
Publication year: 2016
Journal: Acta Oncologica
Volume: 55
Issue: 2
First page : 188
Last page: 192
Number of pages: 5
ISSN: 0284-186X
DOI: https://doi.org/10.3109/0284186X.2015.1062538
Abstract
Background. Prolonged steroid hormone therapy increases the risk of breast cancer, especially the risk of lobular cancer, but the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) use is controversial. In this study we aimed to test the hypothesis that risk for lobular breast cancer is elevated among LNG-IUS users.
Material and methods. We identified from the national Medical Reimbursement Registry of Finland the women aged 30–49 who had used LNG-IUS for the treatment or prevention of menorrhagia in 1994–2007, and from the Finnish Cancer Registry breast cancers diagnosed before the age of 55 and by the end of 2012.
Results. A total of 2015 women had breast cancer diagnosed in a cohort of 93 843 LNG-IUS users during follow-up consisting of 1 032 767 women-years. The LNG-IUS users had an increased risk for both ductal breast cancer [standardized incidence ratio (SIR) 1.20, 95% confidence interval (CI) 1.14–1.25] and for lobular breast cancer (SIR 1.33, 95% CI 1.20–1.46), as compared with the general female population. The highest risk was found in LNG-IUS users who purchased the device at least twice, whose SIR for lobular cancer was 1.73 (95% CI 1.37–2.15).
Conclusions. The results imply that intrauterine administration of levonorgestrel is not only related to an excess risk of lobular breast cancer but also, in contrary to previous assumptions, to an excess risk of ductal breast cancer.
Background. Prolonged steroid hormone therapy increases the risk of breast cancer, especially the risk of lobular cancer, but the effect of the levonorgestrel-releasing intrauterine system (LNG-IUS) use is controversial. In this study we aimed to test the hypothesis that risk for lobular breast cancer is elevated among LNG-IUS users.
Material and methods. We identified from the national Medical Reimbursement Registry of Finland the women aged 30–49 who had used LNG-IUS for the treatment or prevention of menorrhagia in 1994–2007, and from the Finnish Cancer Registry breast cancers diagnosed before the age of 55 and by the end of 2012.
Results. A total of 2015 women had breast cancer diagnosed in a cohort of 93 843 LNG-IUS users during follow-up consisting of 1 032 767 women-years. The LNG-IUS users had an increased risk for both ductal breast cancer [standardized incidence ratio (SIR) 1.20, 95% confidence interval (CI) 1.14–1.25] and for lobular breast cancer (SIR 1.33, 95% CI 1.20–1.46), as compared with the general female population. The highest risk was found in LNG-IUS users who purchased the device at least twice, whose SIR for lobular cancer was 1.73 (95% CI 1.37–2.15).
Conclusions. The results imply that intrauterine administration of levonorgestrel is not only related to an excess risk of lobular breast cancer but also, in contrary to previous assumptions, to an excess risk of ductal breast cancer.
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