A weak connection between IUDs and breast cancer
Expert
Gideon Meyerowitz-Katz: Epidemiologist, chronic disease focus, University of Wollongong
Question
Are IUDs giving women breast cancer?
Reality
A research letter was recently published in the Journal of the American Medical Association suggesting a link between between hormonal IUDs and breast cancer risk. As Meyerowitz-Katz points out, the letter was just 758 words long with few references.
While the authors of the letter found a 40% increase in breast cancer risk, Meyerowitz-Katz notes numerous weakness to the methodology.
Absolute risk was very small among women studied
The study was “extremely minimal” and included no causal modeling
No evidence that longer use of an IUD was associated with a greater risk of cancer
Meyerowitz-Katz also found their focus on only breast cancer odd, as a more robust study from Sweden recently revealed more in-depth data on this topic.
In this study, women who used IUDs also had an increased risk of breast cancer. However, this risk was offset by a reduced risk of endometrial, ovarian, and cervical cancers. The authors of the study also argued that the increased risk of breast cancer may have simply been due to confounding factors rather than a causal connection.
