medwireNews: Women who undergo assisted reproduction may be at increased risk for in situ breast cancer, and invasive and borderline ovarian tumors, show results of a large, population-based study.
However, the researchers note that the increased risk for ovarian cancer was limited to women with other known risk factors and requires further investigation.
The study included all women (n=255,786) who had assisted reproduction in Great Britain between 1991 and 2010, as recorded by the Human Fertilisation and Embryology Authority.
During an average 8.8 years of follow-up, there were 409 cases of ovarian cancer among the women who underwent assisted reproduction. This was significantly higher than the 292 expected in the general population according to period specific national incidence rates and resulted in a standardized incidence ratio (SIR) of 1.39 and an absolute excess risk (AER) of 5.0 cases per 100,000 person–years. In addition, the risk increased significantly with decreasing age at first fertility treatment.
For invasive ovarian cancer, the SIR was a significant 1.40 (264 observed vs 188 expected cases) and the AER was 3.4 cases per 100,000 person–years, while for borderline ovarian tumors the corresponding figures were a significant SIR of 1.36 (141 observed vs 104 expected cases) and an AER of 1.7 cases per 100,000 person years.
The researchers note that the increased risk for ovarian tumors was limited to women with endometriosis, low parity, or both, with no excess risk seen among those treated for unexplained infertility or infertility due to male factors only, and no association with the number of treatment cycles.
This “argues against a causal role for assisted reproduction procedures” in the risk for ovarian cancer, Alastair Sutcliffe (Institute of Child Health, London, UK) and co-authors remark in The BMJ.
Sutcliffe and team also observed a small but significantly increased risk for in situ breast cancer, with an SIR of 1.15 (291 observed vs 254 expected cases) and an AER of 1.7 cases per 100,000 person years, which was significantly associated with the number of treatment cycles.
By contrast, there was no significantly increased risk for breast cancer overall, invasive breast cancer, or corpus uteri cancer among the women who underwent assisted reproduction.
Sutcliffe et al conclude: “Our results suggest that ovarian tumour risks could be due to patient characteristics, rather than assisted reproduction itself, although both surveillance bias and the effect of treatment are also possibilities.”
They add: “Further investigation of this and longer follow-up is warranted to continue monitoring these important outcomes in this ever growing population.”
By Laura Cowen
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