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In vitro fertilization not associated with increased risk for breast cancer
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Women undergoing in vitro fertilization did not demonstrate an increased risk for breast cancer compared with women undergoing other fertility treatments and the general population, according to an analysis of the OMEGA study.
In vitro fertilization (IVF) procedures temporarily cause both elevated and decreased estradiol and progesterone levels at different phases, which may influence breast cancer risk.
“Knowledge about possible long-term influences of ovarian stimulation for IVF on breast cancer risk is still scarce, because IVF did not become widespread until the late 1980s,” Alexandra W. van den Belt-Dusebout, PhD, researcher at Netherlands Cancer Institute in Amsterdam, and colleagues wrote. “Because of the high incidence of breast cancer and the large numbers of women undergoing ovarian stimulation for IVF, even a small risk increase would have important public health implications.”
Van den Belt-Dusebout and colleagues used data from the OMEGA study — which included 25,108 women (median age, 32.8 years) who underwent fertility treatment at one of 12 Netherlands fertilization clinics between 1980 and 1995 — to evaluate the long-term risk for breast cancer after IVF.
Researchers compared cancer incidence between women who underwent ovarian stimulating IVF (n = 19,158; median age at follow-up, 53.8 years) and those who underwent non-IVF fertilization (n = 5,950; median age at follow-up, 55.3 years).
After a median follow-up of 21.1 years, 839 cases of invasive breast cancer and 109 cases of in situ breast cancer occurred in the cohort.
Breast cancer incidence did not significantly increase for women in the IVF group compared with women in the non-IVF group (standardized incidence ratio = 1.01; 95% CI, 0.86-1.19) or the general population (SIR = 1.01; 95% CI, 0.93-1.09).
Cumulative breast cancer incidence did not appear to increase for women aged 55 years in the IVF group compared with the non-IVF group (3% vs. 2.9%). However, these data did not reach statistical significance.
Breast cancer incidence did not increase 20 or more years following fertilization treatment for women in the IVF group (SIR = 0.92; 95% CI, 0.73-1.15) and non-IVF group (SIR = 1.03; 95% CI, 0.82-1.29).
Women who received seven or more treatment cycles of IVF had significantly lower risk (HR = 0.55; 95% CI, 0.39-0.77) than women who received one or two treatment cycles (HR = 0.77; 95% CI, 0.6-0.96).
The risk for breast cancer did not differ based on the type of fertility drugs used or subfertility diagnosis.
Researchers acknowledged several potential limiting factors which may have confounded findings, including missing data on subfertility diagnosis and lack of information on age at menopause and menopausal status at end of follow-up.
“The results of the current study are consistent with recent reviews that reported no increased breast cancer risk after IVF, and are based on a median follow-up of 21.1 years after IVF compared with a mean of 8 years and 16 years in prior studies,” van den Belt-Dusebout and colleagues wrote. – by Nick Andrews
Disclos ure: Van den Belt-Dusebout reports no relevant financial disclosures. Please see the full study for a list of all other researchers' relevant financial disclosures.
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