Breast cancer risk reassurance for IVF-treated women
medwireNews: Women who receive in vitro fertilisation (IVF) treatment do not have a higher risk of developing breast cancer in the long term versus those who receive non-IVF therapy and the general population, say Dutch researchers.
They report on 25,108 participants of the OMEGA historical cohort, 19,158 of whom underwent IVF between 1983 and 1995, while 5950 had other fertility treatments (eg, tubal surgery) between 1980 and 1995 in the Netherlands.
A total of 839 cases of first invasive breast cancer and 109 of ductal carcinoma in situ were recorded over a median follow-up of 21.1 years, according to the study published in JAMA.
Neither IVF-treated women nor those in the non-IVF group had an elevated breast cancer risk relative to the general population, with standardised incidence ratios (SIRs) of 1.01 and 1.00, respectively.
And longer time since IVF or non-IVF treatment (≥20 years) did not affect breast cancer risk either, with respective SIRs of 0.92 and 1.03.
When the two groups that received fertility therapy were compared, the cumulative incidence of breast cancer at 55 years of age was a comparable 3.0% in the IVF group and 2.9% in the non-IVF group. And the risk of breast cancer did not differ significantly between groups, with a hazard ratio of 1.01 after adjusting for age at first birth and parity.
Among IVF-treated participants, receipt of seven or more IVF cycles versus one or two cycles reduced the risk of long-term breast cancer by a significant 45%. A poor response to the first IVF cycle – that is, collection of fewer than four oocytes – also significantly protected against breast cancer, lowering the risk by 23%.
Investigator Flora van Leeuwen, from the Netherlands Cancer Institute in Amsterdam, and co-workers emphasize that “[t]hese findings are consistent with absence of a significant increase in long-term risk of breast cancer among IVF-treated women.”
But they caution: “Because more recent IVF regimens largely consist of protocols with antagonists and shorter periods of down-regulation (possibly associated with less risk reduction), and improved success rates (associated with fewer cycles), it is uncertain how study results generalize to more contemporary IVF treatment.
“Furthermore, because only 14% of the cohort had reached age 60 years, follow-up is necessary to evaluate postmenopausal breast cancer risk after ovarian stimulation for IVF.”
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