Study: Breastfeeding may lower risk of ovarian cancer in women with BRCA mutations

Contents

STUDY AT A GLANCE

What this study is about:

Researchers studied how breastfeeding impacts the risk of ovarian cancer in women who have an inherited mutation in a BRCA1 or BRCA2 gene.

Why is this study important?

People with an inherited BRCA1 or BRCA2 mutation have an increased lifetime risk for several different types of cancer, including breast and ovarian cancer. The lifetime risk for breast cancer for women with a BRCA1 mutation is about 65% and about 55% for women with a BRCA2 mutation. The lifetime risk for ovarian cancer is about 40% for women with a BRCA1 mutation and 20% for women with a BRCA2 mutation. These cancers are more likely to occur at a younger age compared with women in the general population. Breastfeeding offers health benefits to both the mother and baby.

Young women of childbearing years who have a BRCA mutation face difficult decision related to family planning and cancer risk management. Breast cancer screening with mammogram or MRI during pregnancy, carries risks for the baby. Further, experts do not recommend MRI or mammograms during nursing – when the breasts are full of milk and hard to image. For these reasons, some high-risk women choose to have risk reducing mastectomy before pregnancy. Other women may avoid breast feeding or stop early in order to resume high-risk screening as soon as possible.

Women with mutations have limited options for lowering their ovarian cancer risk. These include oral contraceptives surgery to remove the ovaries and fallopian tubes (salpingo-oopherectomy). There is an ongoing clinical trial looking at risk-reduction with early fallopian tube removal followed by delayed ovary removal (read our XRAY review on the topic, a procedure called risk-reducing early salpingectomy with delayed oophorectomy, or RRESDO), but this surgery has not been proven to lower risk.

Previous research showed breastfeeding may lower risk of ovarian cancer up to 24 percent in women in the general population who are in their childbearing years. The protective effect was greater in women who breastfeed more than 12 months. Researchers wanted to know if breastfeeding offers similar protection in women with inherited mutations in BRCA1 or BRCA2.

This study looked at the effects of breastfeeding on ovarian cancer risk in women with a BRCA1 or BRCA2 mutation. 

Study findings 

The study included more than 4,300 women with an inherited BRCA1 or BRCA2 mutation. Women with or without a history of ovarian cancer were included in the study. Participants completed questionnaires once every two years on the following topics:

• Family or personal history of cancer
• History of breastfeeding and pregnancy
• Use of oral contraceptives to prevent pregnancy (e.g., birth control pills)

Study findings showed that:

• Women diagnosed with ovarian cancer were less likely to report ever having breastfed, compared with women who didn’t have ovarian cancer.
• Women who breastfed had a 23 percent lower risk of ovarian cancer.
  • Women who breastfed for seven or more months had a 32 percent lower risk of ovarian cancer.
  • Women who completed childbearing prior to age 35 and breastfed had a 19 percent lower risk of ovarian cancer.
  • Women who gave birth at age 35 or older and breastfed had a 40 percent lower  ovarian cancer risk.
• A history of oral contraceptive use increased the effect of breastfeeding. Women who had taken oral contraceptives and breastfed seven months or longer in their lifetime had a 45 percent lower risk of ovarian cancer. 

Strengths

• The study looked at multiple factors that had been previously shown in the general population to influence the impact of breastfeeding, such as length of breastfeeding and use of oral contraceptives.
• The study size was large, which increases the chances that the findings are real and not due to chance.

Limitations

• The study did not mention the race or ethnicity of patients. This is important because race and ethnicity may impact cancer risk.  
• The study was limited to women with either an inherited BRCA1 or BRCA2 mutation. It did not include women with inherited mutations in other known ovarian cancer genes.
• Because this was an observational study, we cannot say for certain that breastfeeding lowers the risk for ovarian cancer in women with BRCA mutations.

What does this mean for me?

Breastfeeding offers several benefits for both the mother and baby, including possible protection against ovarian cancer for mothers. This study suggests that this benefit may also apply to women with a BRCA1 or BRCA2 inherited mutation. This study also highlights the benefit of oral contraceptives in reducing ovarian cancer risk in women with these mutations.

If you have a  BRCA1 or BRCA2 mutation and you are considering having children, you should discuss your options for managing cancer risk before, during and after pregnancy with your doctor. If you are already pregnant or breastfeeding, you may want to discuss the benefits and risks of breastfeeding and the impact on breast screening with your doctor.

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Posted 1/28/21

References

• Kotsopoulos J, Gronwald J, McCuaig J, et al. Breastfeeding and the risk of epithelial ovarian cancer among women with a BRCA1 or BRCA2 mutation. Gynecology Oncology. 2020;159(3):820-826.
• Babic A, Sasamoto N, Rosner B, et al. Association Between Breastfeeding and Ovarian Cancer Risk. JAMA Oncology. 2020;6(6):e200421. Published online April 2,2020.

Disclosure

FORCE receives funding from industry sponsors, including companies that manufacture cancer drugs, tests and devices. All XRAYS articles are written independently of any sponsor and are reviewed by members of our Scientific Advisory Board prior to publication to assure scientific integrity.