October is Breast Cancer Awareness Month. In honor of this month of awareness, Pacific Fertility Center wants to share the recent results of a long-term follow-up study conducted in the Netherlands, which has found that there is no link between in vitro fertilization (IVF) and an increased risk of breast cancer. In fact, among women undergoing IVF, the risk of breast cancer did not differ significantly from that in the general population.

In the past, a variety of studies suggested that in vitro fertilization (IVF) might be a risk factor for breast cancer. However, these findings were inconclusive because follow-up was limited. Therefore, the Dutch researchers chose to assess the long-term risk of breast cancer after ovarian stimulation for IVF.

Large study, long follow-up.

The researchers collected information from mailed questionnaires and medical records from all 12 IVF clinics in the Netherlands. They assessed rates of breast cancer through the Netherlands Cancer Registry, looking at a median follow-up period of more than 21 years.

The researchers analyzed risks in more than 19,000 women who had started IVF between 1983 and 1995 (IVF group), as well as nearly 6,000 women who started other types of fertility treatment between 1980 and 1995 (non-IVF group). At the end of the follow-up period, the median age was 53.8 years for the IVF group and 55.3 years for the non-IVF group.

Reassuring results.

After more than two decades, there was a total of 839 cases of invasive breast cancer and 109 cases of in situ breast cancer. The cumulative incidence of breast cancer in the IVF group was virtually identical to that in the non-IVF group. Incidences of breast cancer at age 55 were 3.0 percent for the IVF group and 2.9 percent for the group using other types of fertility treatment.

Interestingly, the risk of breast cancer was significantly lower for women who had 7 or more IVF cycles compared with those who had only 1 or 2 cycles and compared to those who had a poor response to their first IVF cycle. Although this trend was not large, the researchers suspect exposing women to high levels of estrogen and progesterone during IVF treatment may be protective, just as the hormonal milieu of pregnancy is protective against breast cancer.

In the study, a subset of women who had had IVF experienced an increase in breast cancer risk. Women who previously had given birth had a significant increased risk compared with women who had not. In addition, women first giving birth at age 40 were twice as likely to develop breast cancer as women who were younger.

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1. Van den Belt-Susebout, A. et al. Ovarian Stimulation for In Vitro Fertilization and Long-term Risk of Breast Cancer. JAMA. 2016;316(3):300–312.
2. Oncology Nursing News: Longitudinal Study Finds No Increased Risk of Breast Cancer From IVF
3. MedPage Today: No Breast Cancer Risk Seen With IVF