Some time ago, a woman with breast cancer gave her doctor, oncologist Cristina Saura, some samples of breast milk that she had frozen 18 months before the diagnosis. The tumor was detected when she was pregnant with her third child and the woman feared that she had transmitted the disease through breast milk to her second daughter, whom she breastfed until shortly before she became ill. Saura and her team knew that the tumor is not transmitted through breastfeeding, but due to the patient’s concern, “a light bulb went on,” explains the oncologist: perhaps in that milk sample there were already signs of cancer. to help the investigation.
And they found something: in that frozen food many months before the cancer diagnosis, there was already tumor DNA that revealed the presence of cancer in the body. In a subsequent study with fifteen patients and published in the journal Cancer Discovery, Saura and his team at the Vall d’Hebron Institut d’Oncologia (VHIO) in Barcelona confirmed the presence of tumor DNA fragments in breast milk. The research opens the door to using the analysis of this fluid as a tool to diagnose breast cancer early in the postpartum.
The liquid biopsy technique has shaken cancer research. This diagnostic approach consists of searching the body’s fluids, especially the blood, for signs or traces of a tumor before it shows its face, such as the pieces of DNA that cancer cells release into the bloodstream. In this way, with a type of blood test (much less invasive than a traditional biopsy) the presence of tumors that are still invisible can be detected. Liquid blood biopsy has already been tested for colon or breast cancer, but also cerebrospinal fluid biopsy in brain tumors, urine biopsy in bladder neoplasms, or saliva biopsy in oral cancer. Breast milk is the new body fluid in close contact with a tumor that now shows its potential in the early diagnosis of the disease in a particularly complex stage, such as the postpartum period.
The finding lands in a field, that of pregnancy and lactation, where all the variables play against each other. Starting with the incidence. Breast cancer is the most common detected in these stages: “Breast tumor diagnosed in the postpartum or pregnancy represents up to 55% of tumors diagnosed under the age of 45,” warns Saura. And the forecast is that “cases will increase in the coming years,” the researchers warn in the study, taking into account that aging increases the risk of this disease and that there is a tendency to delay pregnancy in developed countries. In addition to the fact that the incidence is increasing, in these contexts, this condition usually has a complex diagnosis and, sometimes, a more unfavorable prognosis.
Following the request of that Saura patient, Vall d’Hebron researchers began a study and analyzed breast milk and blood samples from fifteen women with breast cancer and another dozen healthy volunteers. “In women who have breast cancer diagnosed during pregnancy or breastfeeding, we find circulating tumor DNA in breast milk. In 13 of the 15 patients, the (milk) samples were positive,” explains Saura, who is head of the Breast Unit at Vall d’Hebron Hospital and head of the VHIO Breast Cancer Group. In the other two, the samples collected were colostrum (first milk) and the researchers suspect that the tests were negative because the tumor DNA did not have time to come into contact with this fluid. “It takes several days for the DNA to be released from the cells. We believe that (with colostrum) not enough milk has been produced to carry tumor DNA,” says the oncologist. The frequencies of the variants detected in colostrum, in fact, were “almost seven times lower compared to those collected after 14 days of lactation and considered mature samples,” the study states. In the analyzes of the milk of the healthy volunteers, no traces of the tumor were found.
The researchers also found that the sensitivity of breast milk tests was higher than that of blood samples, which were almost all negative. “It was expected,” says Saura, because, in breast cancer, to find tumor DNA in a liquid blood biopsy, a high burden of disease is needed (for example, when there is metastasis). “With a localized tumor, the amount of tumor DNA in the blood is always low. On the other hand, in milk we are already able to detect tumor DNA,” explains the doctor.
Towards an early diagnosis test
With the study, scientists demonstrated, for the first time, that the breast milk of breast cancer patients has enough tumor DNA to detect it through a liquid biopsy, even before the diagnosis can be made with conventional imaging tests. Saura points out that the results of the study open the door to developing an early diagnosis test in the postpartum in women who decide to breastfeed, but admits that this finding is still the first step.
Teresa is one of the participants in the study and her case, like that of the first patient who triggered the investigation, illustrates the potential of this detection technique: she was healthy when she became pregnant, but she was 46 years old and, due to the risk factor age, wanted to participate in the study. “At 18 months (after the child was born), in one of the trial controls (a follow-up breast ultrasound) they detected the tumor and I put myself in their hands. Since it was detected at an early stage, no chemotherapy was necessary. I had surgery and received radiotherapy,” explains the 50-year-old woman on the other end of the phone. However, in the analysis of breast milk samples taken, within the trial, 11 months after delivery (half a year before diagnosis by breast ultrasound), fragments of tumor DNA were already visible. This means that, with this technique, the diagnosis could have been brought forward six months, defend the authors of the study.
The research is still ongoing and to realize the potential of their discovery, Saura and her team have also developed a panel of genes with the most frequent mutations present in women with cancer diagnosed before the age of 45. As happens with the heel test in babies to detect congenital metabolic ailments, this panel, which will be used to analyze breast milk samples, could also function as an early diagnosis method in the postpartum, the researchers predict. “The third step, for this to translate into a useful early diagnosis test, is to demonstrate it and we will do a study in which 5,000 healthy women at risk of breast cancer will be included (over 40 years of age and/or with a genetic predisposition). from whom a blood sample will be taken, as well as another milk sample from each breast, they will undergo an ultrasound and will be followed up for two years,” says Saura.
Joan Albanell, head of the Oncology Service at the Hospital del Mar in Barcelona, calls this research, in which he has not participated, “innovative”: “At a clinical level, the impact has yet to be determined, but it is a conceptual advance,” he agrees. . The doctor highlights that, according to this study, breast milk “is a more reliable source for detecting circulating tumor DNA” and he opens the door to, with liquid biopsy, “the diagnosis can be brought forward.” But Albanell is cautious about the times: “To see if this can be translated into systematic patient screening, multicenter studies are needed to validate the value and efficiency of the technique.”
Saura insists that, “if everything goes well, there will be a new tool for the early detection of breast cancer in the postpartum.” In practice, specifically, this can mean an improvement in prognosis and survival because tumors can be “detected when they are localized”, in earlier stages.
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Source: EL PAIS