Breastfeeding Lowers the Risk of Ovarian Cancer, According to New Research
Speaking with Australian and International leader in Ovarian Cancer Epidemiology, Professor Penny Webb of QIMR Berghofer Medical Research Institute, we unpack her latest research conducted with colleagues at Harvard and the University of Pittsburgh , which outlines findings around the associations between breastfeeding and a lowered risk of developing ovarian cancer.
The data presented in the paper states that breastfeeding was associated with a 24% lower risk of invasive ovarian cancer and 28% decrease in borderline tumour risk. In those women who had ever breastfed, there was a reduction in risk of all invasive ovarian cancers, particularly high-grade serous and endometrioid cancers.
We reached out to Professor Webb to gain more insight into the findings and to understand how they related to women who have an increased risk of being diagnosed with ovarian cancer due to family history.
What prompted you to look at breast feeding and ovarian cancer associations?
Prof Webb: We know that women who have more children, or use the oral contraceptive pill, have a lower risk of developing ovarian cancer than women who have fewer or no children or who don’t use the pill.
When a woman is pregnant or on the pill she does not ovulate and the same is true for at least the first few months of breastfeeding after a baby is born, so we believed it plausible that breastfeeding might also reduce risk of ovarian cancer.
Some previous studies had suggested this might be the case but the data was not consistent so we wanted to look at this in a much larger study where we could clearly separate any effects of breastfeeding from the effects of pregnancy.
What is your top piece of advice for women based on your findings in the study?
Prof Webb: Breastfeeding has been associated with a number of health benefits for both the mother and her baby; it now seems we can add a lower risk of developing ovarian cancer to the list of benefits for the mother.
I would suggest that, if possible, women follow the World Health Organisation guidelines that recommend women should, where possible, breastfeed for at least 6 months and ideally up to 1 or 2 years (with complementary foods).
Why is breastfeeding associated with a lower risk of ovarian cancers?
Prof Webb: We don’t really know. It is probably partly due to the fact that breastfeeding suppresses ovulation in the first few months after a baby is born (other factors that suppress ovulation like pregnancy and contraceptive pill use also reduce risk) but this can’t explain all of the association.
Breastfeeding may also affect other biological pathways, for example those involved in inflammation, the immune response or other metabolic pathways and these might be important.
Does breast feeding provide a reduction in risk for a woman who is already at an increased risk due to family history and mutated genes?
Prof Webb: This study saw a similar reduction in risk for women who had a family history of ovarian cancer.
We could not look directly at women who had a genetic mutation in one of the BRCA genes because this information was not available. A previous study https://breast-cancer-research.biomedcentral.com/articles/10.1186/bcr3138 has suggested that breastfeeding also reduces risk for BRCA1 carriers but in that study the benefit for BRCA2 carriers was less clear, although they had a smaller number of women in that group.
As there is no screening for Ovarian Cancer, what other recommendations do you have for women managing a higher risk of ovarian cancer?
Prof Webb: If women are at a higher risk of ovarian cancer because they carry a genetic mutation in a known ovarian cancer gene they should discuss the options open to them with their healthcare provider. Unfortunately, the only ways to greatly reduce risk probably involve surgery (removal of the ovaries and fallopian tubes or, perhaps, just the tubes – however this is still being investigated).
Factors associated with a healthier lifestyle (not smoking, being of normal body weight, physical activity) have been associated with a lower risk of developing ovarian cancer overall but the effects are quite small.
Are you working on any other interesting studies at the moment that relate to ovarian/breast cancer management and risk?
Prof Webb: Most of my work at the moment is looking at women already diagnosed with ovarian cancer and whether potentially modifiable aspects of lifestyle might prevent the cancer from coming back and/or improve survival rates.
Is it important to remind women that even if they have breastfed their children, they should continue to monitor their ovarian health and not become complacent?
Prof Webb: Absolutely. Although women who breastfeed have a slightly lower risk of developing ovarian cancer compared to women who have not breastfed, this does not mean that they will not develop ovarian cancer. A high proportion of women who do develop ovarian cancer have breastfed in the past. It is also important to note that ovarian cancer is relatively uncommon so, even if a woman did not breastfeed her children, or if she has not had children, her risk of developing ovarian cancer is still very low.
Professor Penny Webb is a cancer epidemiologist specialising in women’s cancers. She received her PhD from Oxford University before moving to Brisbane in 1995. She now heads the Gynaecological Cancers Group at the QIMR Berghofer Medical Research Institute and leads studies that aim to identify factors that influence risk of, and survival following ovarian and endometrial cancer.