Breast milk could be key to early-stage breast cancer detection

Just a drop could save your life

A game-changing discovery of tumour DNA within breast milk is set to redefine how health professionals screen for the disease, promoting more accurate and life-saving diagnoses for women everywhere. 

Breast milk has long been championed for its ability to promote healthy development and boost immunity for a growing newborn. Now, it seems the natural liquid may be packing another lifesaving benefit. 

A recently published study has revealed the presence of tumour DNA circulating in breast milk. The discovery is set to alter the course of breast cancer screening and treatment for pregnant and postpartum women, some of the most vulnerable to breast cancer mortality rates. 

According to Christina Saura, PhD, and head of the team responsible for the groundbreaking research at the Vall d'Hebron Institute of Oncology (VHIO) in Spain, pregnant and postpartum women often tend to receive their cancer diagnoses in advanced stages.  

“It is typically assumed that the physiological changes in the breasts during gestation and lactation, which are considered to be normal, may hide a developing tumour, explains Saura. “The fact is that postpartum breast cancer, understood to be the ten years after delivery, accounts for 40 per cent to 45 per cent of breast cancer cases diagnosed before age 45."

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With such sombre statistics, researchers across the globe have been tirelessly working to uncover more effective and accessible methods for early detection. The latest discovery could now see women receiving an early diagnosis based on a simple liquid biopsy of their breast milk.

A surprise discovery 

According to Saura, the idea to test breast milk for any detection of breast cancer came from one of the institute’s patients, a woman diagnosed during her third pregnancy. Paranoid her tumour may have been transmitted to her second child before she was unaware of her diagnosis, she asked her doctors to test a sample of her breast milk she had kept stored in a freezer.  

“Though we knew that breast cancer is not transmitted through breast milk, we decided to test the sample and look for markers that could help our research,” explains Saura, on the institute’s subsequent discovery of DNA with the same mutation that was present in her tumour. 

With the milk sample having been stored in the freezer for more than a year, Saura and her team realised the potential breast milk had in offering a more accurate, early-stage detection method than other current screening techniques.

The initial test, conducted on a year-old frozen breast milk sample, uncovered findings that surprised researchers. Image: iStock

The subsequent research

The VHIO research team used two different techniques to analyse both breast milk and blood samples: next-generation sequencing and droplet digital polymerase chain reaction. Ana Vivancos, PhD and another author of the study, explains both methods confirmed the presence of ctDNA in breast milk, shining a light on the liquid’s association with earlier and more accurate detection. 

"We were able to detect tumour mutations in milk samples from 13 of the 15 patients with breast cancer who were tested, while circulating tumour DNA was detected in only one of all the blood samples that were collected at the same time," says Vivancos. 

Using a genomic panel calibrated to detect the genes that are most frequently mutated in breast cancer in women under the age of 45, the team found their breast milk screening model extremely effective in identifying early-stage tumours.  

"In practice, the panel design allows us to detect mutations in more than 95 per cent of breast cancer cases in women under 45 years old. Therefore, using this panel for early detection of this type of tumour during lactation should contribute to addressing a medical need that, until today, has gone unmet," explains Vivancos.

The findings indicate it may be possible to diagnose breast cancer in postnatal women long before conventional imaging techniques would detect any abnormalities. Image: iStock

Could this test revolutionise breast cancer screening?

Given no screening techniques currently offer pregnant women an opportunity for early detection, this groundbreaking research could significantly increase the survival rate for women diagnosed with breast cancer during pregnancy, "That's exactly the goal of this research: to screen for breast cancer in women who have just given birth,” Saura says. 

Unlike existing screening methods, this breast milk biopsy is non-invasive and painless, only requiring a milk sample from women after birth. So far, the method has also proven to be significantly more accurate than similar techniques involving blood samples. 

"We have seen that breast milk liquid biopsy was positive for the presence of circulating tumour DNA in 87 per cent of cases, whereas blood only revealed the presence of this marker in 8 per cent of cases,” says Saura. “This difference indicates that breast milk is a biofluid that is in more direct contact with tumour cells and therefore will be more informative in earlier stages."

With further funding and research, the team at VHIO hope breast milk liquid biopsy will soon become a widely accepted screening method around the world for women of childbearing age. 

Originally published as Breast milk could be key to early-stage breast cancer detection