October is Breast Cancer Awareness Month. This is a crucial time to raise awareness about screening, treatment, and prevention of breast cancer. PhD student, Sophia D’Alessandro from the Department of Surgery and Cancer examines her research looking at the link between breastfeeding and the reduced risk of breast cancer in our latest blog.
Breast cancer is one of the most prevalent cancers in the world, alongside prostate, lung and colorectal cancer. It is estimated that there are more than 150 new cases diagnosed every day. But why does breast cancer occur? We know cancer is a multifactorial disease caused by a variety of different factors, which can include mutations in key cancer-causing genes, and lifestyle-related risk factors such as age, being overweight, smoking, family history of breast cancer and hormone therapies. However, there are also factors that can reduce a person’s risk of breast cancer risk, such as breastfeeding.
Current research suggests that the risk of developing breast cancer decreases by 4% for every 12 months of breastfeeding. But it’s not yet clear why. The primary function of the human breast is to produce nutrient rich milk for babies. Therefore, the complex structure of the breast is designed for this function. It is comprised of fatty adipose tissue, surrounding lobules and ducts. The lobules produce milk, and the ducts transport it to the nipple, where it can be expelled and fed to a baby. In addition to this, the ducts of the breast are lined by a layer of specialised cells known as epithelial cells. It has been shown previously that breast milk may contain some of these breast epithelial cells, which are then digested in the babies’ stomach and cause them no harm. However, around 85% of breast cancer cases arise from the epithelium, so it is thought that the loss of mutated breast epithelial cells through breastfeeding may play a role in reducing breast cancer risk.
Why does breastfeeding protect you from breast cancer?
One hypothesis for how breastfeeding reduces risk is by extending the period of low oestrogen that all women experience after birth. Since oestrogen is a key driver of breast cancer growth, this seems a plausible explanation. Another potential reason for this positive effect is that breast epithelial cells in breast milk contain a low frequency of mutations in tumour p53, a key gene in cancer development. If these cells are potentially pre-cancerous cells, and they are being exfoliated during breast feeding, then it is possible that this could be a mechanism by which breast feeding reduces breast cancer risk.
Current research at Imperial College London aims to answer some of these questions and improve our understanding of breast cancer risk and prevention, using breast milk samples donated by 300 women taking part in the Breastmilk Epigenetics Cohort Study (BECS), coordinated in partnership with the Human Milk foundation. As well as this, we also want to find out whether factors such as weight, exercise, or smoking are linked to the presence of the cells.
Early diagnosis and treatment
Early diagnosis and treatment are highly desirable, as the 5-year relative survival rate of female patients diagnosed at stage I is over 98%, compared to only 25% if diagnosed at stage IV, where the cancer has likely metastasised – tumour cells have transferred to distant organs such as the lung, liver, brain, and bone. Younger women tend not to have regular mammograms or other breast screening tests, so the potential to use breast milk in these younger individuals may help to promote early diagnosis, which we know is beneficial for cancer prognosis. Further to this, this project might provide evidence for the mechanism by which prolonging breast feeding can reduce risk, which would strengthen the public health messaging supporting the benefits of breastfeeding for longer and potentially identify a biomarker of reducing risk. In turn, this may increase the case for government investment in breast feeding support, which many women currently feel does not meet their needs.
Another important aspect of this study is determining how this information should be conveyed to women and the public in general. In parallel with laboratory research, interviews with some of the women in the BECS study are planned to assess whether they would want to be made aware of the detection of DNA changes in their breast milk and how they might feel about public health messaging that conveys they could be at greater risk. Additionally, if it were possible to identify an individual potential risk from their breast milk samples, would they want to know? Only 48% of women continue to breastfeed beyond 6-8 weeks in the UK, but with the potential benefits of breast feeding for longer, would women want to?
Overall, this research aims to provide not only molecular genetic evidence of the link between breastfeeding and breast cancer, but also an understanding of the potential implications of this research for women, public health and even government policy.