Concern over a relationship between in vitro fertilization (IVF) and subsequent breast cancer has been ameliorated by a large study conducted in Australia. The authors report no overall increase in the rate of breast cancer in women who undergo IVF. However, there does seem to be a higher risk of breast cancer in those who begin IVF treatment when in their mid-20s.
A population-based study from Western Australia studied the incidence rate of breast cancer in a large cohort (n=21,025) aged 20 to 44 years who underwent hospital-based treatment for infertility. Researchers compared the rate of breast cancer in women who had IVF with those who had fertility treatment but not IVF.
The study, published in Fertility and Sterility, reports that there is no overall increase in the risk of breast cancer for women who undergo hospital-based IVF (hazard ratio [HR], 1.10; 95% confidence interval [CI], 0.88–1.36).
“For younger women,” write the authors, “there is some cause for concern, because it appears that they may face an increased risk of breast cancer after IVF treatment.”
Women who began hospital infertility treatment at 24 years of age and required IVF had an unadjusted HR of breast cancer of 1.59 (95% CI, 1.05–2.42) compared with women of the same age who had infertility treatment but no IVF.
When adjusted for late age at first delivery, which is associated with an increased rate of breast cancer, and delivery of twins and higher-order multiples, which is associated with a decreased rate of breast cancer, the HR remained elevated at 1.56 (95% CI, 1.01–2.40).
“The results of this study will be reassuring to women who commence IVF treatment in their 30s and 40s because, for these women, there appears to be no direct association between IVF treatment and breast cancer risk,” write the authors. Risk was not elevated in women who commenced treatment at age 40 and required IVF (adjusted HR, 0.87; 95% CI, 0.62–1.22).
“Nevertheless, women should be aware that delivering their first child late in reproductive life, whether assisted by IVF or not, is associated with an increased risk of breast cancer.”
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