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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
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 or gene.

 

Why is this study important?

People with an inherited or 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 mutation is about 65% and about 55% for women with a mutation. The lifetime risk for ovarian cancer is about 40% for women with a mutation and 20% for women with a 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 mutation face difficult decision related to family planning and cancer risk management. Breast cancer screening with or during pregnancy, carries risks for the baby. Further, experts do not recommend 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 (salpingo-oopherectomy). There is an ongoing clinical trial looking at risk-reduction with early removal followed by delayed ovary removal (read our XRAY review on the topic, a procedure called risk-reducing early with delayed , 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  or .

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

 

Study findings 

The study included more than 4,300 women with an inherited  or  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 or 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 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 or 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   or 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

 

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.

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

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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 or 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 or .
 

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 or . 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 or 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 mutations occur in women worldwide.
  • A relatively large number of participants with or mutations participated in this study, which allows more confidence that the conclusions are sound.
     

Limitations:

  • The study did not separate data by different variants among the participants. Women with different mutations in and different mutations in 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 or mutations. It did not include women with inherited mutations in other known ovarian cancer genes.
     

Context:

Women with inherited mutations in and 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 and mutations.

However, it is important to note that women of childbearing years who have a mutation face difficult decisions related to family planning and cancer risk management. Breast cancer screening with or during pregnancy carries risks for the baby. Further, experts do not recommend 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 or 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 mutation carriers.
 

Share your thoughts on this XRAYS article by taking our brief survey

Expert Guidelines
Expert Guidelines

The National Comprehensive Cancer Network (NCCN) provides guidelines for management of gynecologic cancer risk in people with and mutations. 

Prevention 

  • Risk-reducing removal of ovaries and , (known as salpingo-oophorectomy) is recommended between ages 35-40 for and 40-45 for and upon completion of childbearing.
    • Research studies show that removing the ovaries can increase survival for women with  mutations. 
    • Women should talk with their doctors about the effects of early menopause and options for managing them.
  • Women should talk with their doctors about the risks and benefits of keeping or removing their uterus (hysterectomy), including:
    • Women with a  mutation have an increased risk for a rare form of aggressive uterine cancer; hysterectomy removes this risk. 
    • For women considering hormone replacement after surgery, the presence or absence of a uterus can affect the choice of hormones used.
      • Estrogen-only hormone replacement is less likely to increase the risk for breast cancer, although it increases the risk for uterine cancer. Women who still have their uterus are typically given hormone replacement with both estrogen and progesterone.
      • Adding progesterone to estrogen hormone replacement can protect against uterine cancer. However, the combination of these hormones may increase the risk for breast cancer more than estrogen alone. 
    • A medical history of fibroids or other uterine or cervical issues may justify a hysterectomy. 
  • Oral contraceptives (birth control pills) have been shown to lower the risk for ovarian cancer in women with  mutations. Research on the effect of oral contraceptives on breast cancer risk has been mixed. Women should discuss the benefits and risks of oral contraceptives for lowering ovarian cancer risk with their doctors. 
  • Removal of the  only () is being studied as an option for lowering risk in high-risk women who are not ready to remove their ovaries. Studies on the effects of are ongoing. At this time whether  lowers the risk for ovarian cancer in high-risk women remains unknown. 
    • Consider enrolling in a research study looking at this procedure to lower cancer risk.

Screening

  • There are no proven benefits to routine ovarian cancer screening using transvaginal  and a  blood test. However, some doctors still recommend this screening, starting at ages 30-35.
  • Women should be aware of the symptoms of gynecologic cancer and report abnormalities to their doctors. 

Updated: 08/06/2022

Questions To Ask Your Doctor
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 mutation. What are my options for managing my cancer risk?
  • I have a mutation and I’m considering surgery. What is the best timing?
  • I have a mutation and would like to have children. What issues should I consider in my family planning?
  • I have a mutation and I am pregnant. How and when should I be screened for breast cancer?
  • I have a 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
Open Clinical Trials

The following are studies looking at ovarian cancer screening or prevention.  ​​​​​

Additional clinical trials for ovarian cancer screening and prevention may be found here.

Updated: 09/11/2022

Peer Support
Peer Support

FORCE offers many peer support programs for people with inherited mutations. 

Updated: 08/06/2022

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