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

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Contents

At a glance Questions to ask your provider
Study findings Clinical Trials
What does this mean for me? Related resources and references
Study details Expert guidelines
   

 

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 are ongoing clinical trials looking at risk-reduction with early fallopian tube removal followed by delayed ovary removal (read our XRAY review [link to:

https://www.facingourrisk.org/XRAY/women-support-delayed-ovary-removal], 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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This article is relevant for:

Women considering breastfeeding who have inherited BRCA mutations.

This article is also relevant for:

Women under 45

Previvors

Healthy people with average cancer risk

People with a family history of cancer

People with a genetic mutation linked to cancer risk

Be part of XRAY:

Questions to Ask Your Doctor

  • My family has a history of ovarian and breast cancers. Should I consider genetic testing for an inherited mutation?
  • I have an inherited BRCA mutation. What are my options for managing my cancer risk?
  • I have a BRCA mutation and I’m considering surgery. What is the best timing?
  • I have a BRCA mutation and would like to have children. What issues should I consider in my family planning?
  • I have a BRCA mutation and I am pregnant. How and when should I be screened for breast cancer?
  • I have a BRCA mutation and I am nursing. How should I be screened for breast cancer?
  • Should I consider oral contraceptives? If so, for how long?

Open Clinical Trials

IN-DEPTH REVIEW OF RESEARCH

Study background

A study published in 2020 showed that breastfeeding lowers the risk of advanced ovarian cancer by 24 percent in women. However, it was unknown if this protective effect of breastfeeding extends to women with an inherited mutation in the BRCA1 or BRCA2 genes.

Researchers of this study wanted to know:

If breastfeeding is associated with a reduced risk of ovarian cancer in women with inherited mutations in BRCA1 or BRCA2.
 

Populations looked at in this study

The study included 4,352 women, ranging from ages 18 to 80 at the time of enrollment. Of these women, 1,650 women had ovarian cancer and 2,702 did not.

All participants had an inherited mutation in BRCA1 or BRCA2. They underwent genetic testing prior to the study due to a family or personal history of breast and/or ovarian cancer or due to their involvement in a research study that required genetic testing.
 

Study design:

The study was carried out in 61 clinics located throughout 15 countries.

Participants completed an enrollment questionnaire and follow-up questionnaires every two years afterward. Participants were asked about the following:

  • 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:  

Study findings showed that:

  • women diagnosed with ovarian cancer were less likely to report ever having breastfed, compared with women without ovarian cancer.
  • having ever breastfed was associated with a 23 percent reduction in risk of ovarian cancer.
    • Women who breastfed for seven or more months had a 32 percent reduction in risk of ovarian cancer.
    • Women who completed childbearing prior to age 35 and breastfed had a 19 percent risk reduction of ovarian cancer.
    • Women who gave birth at age 35 or older and breastfed had a 40 percent reduction in 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 reduction of ovarian cancer. 
     

Strengths and Limitations:

Strengths:

  • The study was limited to women with either inherited BRCA1 or BRCA2 mutations to explore the impact of breastfeeding on ovarian cancer onset in this population.
  • The study analyzed 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 was geographically diverse, including women from 15 countries. This is important because BRCA mutations occur in women worldwide.
  • A relatively large number of participants with BRCA1 or BRCA2 mutations participated in this study, which allows more confidence that the conclusions are sound.
     

Limitations:

  • The study did not separate data by different BRCA variants among the participants. Women with different mutations in BRCA1 and different mutations in BRCA2 would be expected to be affected similarly. However, separating the data by the more common mutations could have demonstrated the impact of breastfeeding by mutation.
  • The study did not mention the race or ethnicity of patients. As cancer impacts certain racial and ethnic groups differently, the impact of breastfeeding could also differ among these groups.
  • The study was limited to women with either inherited BRCA1 or BRCA2 mutations. It did not include women with inherited mutations in other known ovarian cancer genes.
     

Context:

Women with inherited mutations in BRCA1 and BRCA2 are at high risk for developing breast and ovarian cancers. These cancers are more likely to occur at a younger age compared with women in the general population.

Currently, few options available to prevent ovarian cancer. Therefore it is crucial to identify factors that may reduce related risk within a woman’s control. Based on the study’s findings, breastfeeding is one factor that is associated with reduced risk for ovarian cancer in childbearing women with inherited BRCA1 and BRCA2 mutations.

However, it is important to note that women of childbearing years who have a BRCA mutation face difficult decisions 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 breastfeeding or stop early to resume high-risk screening as soon as possible.
 

Conclusion:

The current study shows that breastfeeding may reduce the risk of ovarian cancer in women with an inherited BRCA1 or BRCA2 mutation. Although the manner in which breastfeeding protects against ovarian cancer is unknown, future studies are needed to identify the biological mechanism(s) that contribute to risk reduction. This could be used to help develop therapies that mimic the biological action of breastfeeding that may reduce risk of ovarian cancer in BRCA mutation carriers.
 

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