In vitro fertilization and breast cancer: is there cause for concern?

Capsule:
In this research, young women commencing IVF had a subsequent increased rate of breast cancer compared with women seeking infertility treatment at the same age but not requiring IVF.

Authors:
Louise M. Stewart, B.Sc., C. D’Arcy J. Holman, M.P.H., Ph.D., Roger Hart, M.D., Max K. Bulsara, Ph.D., M.Sc., B.Sc., David B. Preen, Ph.D., Judith C. Finn, Ph.D., R.N.

Volume 98, Issue 2 , Pages 334-340, August 2012

Abstract:

Objective:
To examine the incidence rate of breast cancer in a cohort of women undergoing treatment for infertility, comparing the rate in women who had in vitro fertilization (IVF) with those who did not.

Design:
Population-based cohort study using linked hospital and registry data.

Setting:
Hospital.

Patient(s):
All women aged 20–44 years seeking hospital investigation and treatment for infertility in Western Australia during the period 1983–2002 (n = 21,025).

Intervention(s):
None.

Main Outcome Measure(s):
Hazard ratios (HRs) for breast cancer.

Result(s):
There was no overall increase in the rate of breast cancer in women who had IVF (HR 1.10, 95% confidence interval [CI] 0.88–1.36), but there was an increased rate in women who commenced IVF at a young age. Women who commenced hospital infertility treatment at 24 years 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). Hazard ratios were not elevated in women who commenced treatment at age 40 and required IVF (adjusted HR 0.87, 95% CI 0.62–1.22).

Conclusion(s):
Commencing IVF treatment at a young age is associated with an increased rate of breast cancer.

  • Isiah Harris

    Not sure what the mechanism would be, and certainly may be a result of confounding. Not certain I will change my counseling, but certainly a very interesting article.

    • Louise Stewart

      Thanks
      for your comment. We believe the most likely explanation for the finding of an
      increased risk of breast cancer in women who commence IVF treatment at a young
      age is that breast tissue in younger women is more sensitive to the effects of
      elevated levels of circulating estrogen. However, it is true that one
      could not rule out residual confounding as an alternative explanation. But
      in order to explain these results, the confounder (assuming it is associated
      with an increased risk) would need to be more common in women who commence
      infertility treatment in their 20s and undergo IVF, but not more common
      in women who commence infertility treatment in their 30s and 40s and undergo
      IVF. Alternatively, the confounder could be present in women of all ages, but
      only affect women of younger age.

      Thanks
      for your interest in our research.

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