Post-pregnancy, women have an increased risk of breast cancer, and those cancers tend to be more aggressive. A recent study, though, may have found a new diagnostic tool for these postpartum tumors, months before a more conventional diagnosis would be possible.
Researchers from Vall d’Hebron Institute of Oncology in Barcelona recently investigated the ability of breast milk to detect breast cancer. The findings, published in the journal Cancer Discovery, show that it can, with tumor DNA found in the milk of breast cancer patients.
The initial discovery came about when a patient who had frozen her breast milk before her breast cancer diagnosis shared the milk with the researchers. She was diagnosed when she was pregnant with her third daughter and was concerned she may have passed the tumor to her second daughter while breastfeeding.
Dr. Cristina Saura, lead researcher and head of the VHIO Breast Cancer Group and the Breast Unit at Vall d’Hebron University Hospital, explains, “The patient brought us a sample of breast milk that she had stored in her freezer. So, thanks to her, that’s where our project started, because although we know that breast cancer is not transmitted through breast milk, we decided to analyze the sample in search of markers that could help us in our research. And indeed, when we analyzed the patient’s breast milk, we found DNA with the same mutation that was present in her tumor. The breast milk had been frozen more than a year before the patient’s cancer diagnosis.”
From there, the team collected breast milk and blood samples from patients diagnosed while pregnant or postpartum, along with samples from healthy women who were breastfeeding. Using Next Generation Sequencing and Droplet Digital PCR, they found free circulating DNA from tumors in the milk, as well as mutations present in the patients’ tumors in 13 of 15 of their milk samples. With blood samples, though, the tumor DNA was only detected in one patient.
They believe there may be a reason the tumor DNA didn’t turn up in two of the breast milk samples.
Dr. Miriam Sansó, lead author and postdoctoral researcher in the Cancer Genomics laboratory at the time of the study, says, “The breast milk samples of the two patients in whom the mutation was not detected had been collected within the first hours of lactation and were colostrum, so we deduced that probably not enough time had passed for the tumor DNA to have been released into the milk. So we have since decided to take breast milk samples at least two weeks after initiating breastfeeding.”
The team says with their study, they’ve shown that breast milk from breast cancer patients has enough tumor DNA to be detected through liquid biopsy, even before breast cancer can be diagnosed via conventional imaging. Armed with their findings, the researchers developed a Next Generation Sequencing-based genomic panel with a sensitivity of more than 70%, which means seven of 10 cases involved in their study would have been detected with a specificity of 100%.
Dr. Saura says, “This panel could be used in the future as a method for the early diagnosis of breast cancer in the postpartum period. In the same way that a heel prick is performed on all newborns, collecting a breast milk sample from all women after birth for breast cancer screening could also be considered.
“We analyzed the blood and breast milk samples that we had collected in the follow-up at eight and eleven months postpartum and found the cases of high-risk women included in the study further reinforces this idea of using the designed gene panel and liquid breast milk biopsy to advance the early diagnosis of breast cancer.”