A team of researchers from Vall d’Hebron Institute of Oncology (VHIO) from Barcelona (Spain) confirmed that breast milk contains DNA from breast tumors, which opens the door to being used as a liquid biopsy to diagnose cancer in early stages.
The study, published in the journal Cancer Discovery, part of the concern of a breast cancer patient who feared having transmitted the disease to her baby while breastfeeding. She was diagnosed shortly after she had stopped breastfeeding her second daughter and was pregnant with her third.
The head of the Breast Unit at Vall d’Hebron Hospital and VHIO researcher, Cristina Saura, explained to EFE that That patient brought a sample of breast milk that she had stored in her freezer.
“Although we told him that there was no risk of transmitting the tumor, we decided to analyze the sample in search of markers that could help us in the investigation,” he said.
Analysis of milk and cancer
The researchers observed that in this bag, collected about 18 months before diagnosis, there was already DNA from the tumor; known as circulating tumor DNA (ctDNA).
Pulling the string, the researchers collected breast milk and blood samples from more breast cancer patients diagnosed during pregnancy or postpartum. Also, from healthy women who were breastfeeding.
Of 15 cases of women with breast cancer already diagnosed during pregnancy or in the postpartum, in 13 of them the same mutation was detected in the milk as in the tumor they suffered from; instead, in blood samples only one was positive.
“In localized tumors, the release of DNA into the blood is low and very diluted, but in breast milk we see that there is an amount that is easier to detect, making it a potential diagnostic tool,” Saura indicated.
The next step is to start a larger study to collect breast milk samples from 5,000 healthy women worldwide. who have become pregnant at the age of 40 or older, or of any age who carry mutations that increase their risk of suffering from breast cancer (BRCA1, BRCA2, PALB2, RAD51C/D).
The objective is to corroborate whether breast cancer can be detected at an earlier stage in breast milk, even before using imaging techniques or blood tests.
Screening like the heel test
If the results are as expected, Saura has ventured that all women could be screened through breast milk after giving birth, just as is done with newborns in what is known as the heel test to detect a group of diseases.
«We thought it would be useful, because population screening for breast cancer is from the age of 50, through a mammogram, and this new test would be positioned in a -younger- population in which we are not doing tests; and the sooner we diagnose cancer, the more chance we have of curing it,” he stressed.
