A new blood test can accurately identify different types of breast cancer – meaning patients can be matched to the correct treatment without the need for a biopsy.
Researchers have shown that the blood test, called Breast Circulating Methylation Assay (BCMA), can track a cancer’s type over time and pick up if it has changed – meaning that treatment can be quickly adapted.
Each different type of breast cancer requires specific treatment, but around 20% of advanced tumours will switch type, causing treatment to stop working. The researchers - from The Institute of Cancer Research, London - hope their test will ensure patients receive effective treatments sooner, and they believe this technology could be used for other cancers in the future.
The findings, presented at the San Antonio Breast Cancer Symposium, involved analysing blood samples from breast cancer patients in five clinical trials, for circulating tumour DNA (ctDNA) that is released into the bloodstream by cancer cells.
Using machine learning, the scientists, based at the Breast Cancer Now Toby Robins Research Centre at The Institute of Cancer Research (ICR), designed and developed their test to pick up markers on the ctDNA that are specific to each of the main breast cancer types – ER(+ or -), HER2(+ or -) and triple negative breast cancer.
In research funded by Breast Cancer Now, Wellcome Trust, and Cancer Research UK, 191 blood samples from 86 patients were analysed. To check the accuracy of the blood test, the samples were compared with two tissue biopsies that were taken, on average, more than five years apart.
The breast cancer type switched in 19% of these samples, and the BCMA test was almost 90% accurate at identifying this switch.
In 8% of the samples, tissue biopsies showed that the patients’ cancer had switched type – for example, from ER+/HER2- to triple negative breast cancer (TNBC) – but the blood test showed that both types of breast cancer were present at the same time. The researchers say this means patients could benefit from drugs specific to both types of breast cancer, expanding treatment options for them. These include aromatase inhibitors to treat ER+ breast cancers, and targeted drugs for TNBC such as sacituzumab govitecan (also known as Trodelvy). In addition, 29% of tissue samples that were HER2- showed as HER2+ in the blood test – indicating that a greater number of patients may benefit from HER2+ specific therapies than currently receive them.
Dr Nida Pasha, Clinical Research Fellow at The Institute of Cancer Research, London, and first author of the study, said: “Our test detects unique patterns in the tumour DNA circulating in a patient’s blood to pinpoint the exact breast cancer type. This can guide treatment decisions, so the next stage for this research is to assess the test in prospective clinical trials to see if it improves patients’ outcomes by tailoring their therapy. The technology behind this test isn’t limited to breast cancer – it could be applied across many cancer types. I’m excited about a future where non-invasive blood tests like this could become the norm, guiding many more cancer treatment decisions.”
Professor Nicholas Turner, Professor of Molecular Oncology at The Institute of Cancer Research, London, and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust, said: “Treating breast cancer based on its type is the mainstay of breast cancer management but until now, a tissue biopsy has been required to detect that type, and biopsies are generally only taken at diagnosis. Cancers can adapt and evolve, and if we continue treating it based on its initial form, we are unlikely to succeed.
“Unfortunately, we know that around 20% of advanced breast cancers do switch type, and this is a major source of treatment failure if it isn’t identified.Our research is the first to show that it is possible to identify breast cancer’s type from a blood test – meaning that any changes to this type can be tracked easily over time, and treatment can be altered if necessary. This proof-of-principle retrospective study lays the foundation for better monitoring of treatment response, and potentially life-extending treatment in patients.”