Blood Tests Show Promise for Personalized Breast Cancer Treatment Selection
Key Insights
Researchers at The Institute of Cancer Research, London have developed two innovative blood tests that can guide breast cancer (search) treatment decisions without requiring invasive tissue biopsies.
The Breast Circulating Methylation Assay (BCMA) can identify different breast cancer (search) subtypes with nearly 90% accuracy and detect when tumors switch types during treatment.
A separate circulating tumor DNA test can predict treatment response, showing that patients with low ctDNA levels had significantly longer progression-free survival compared to those with higher levels.
Researchers at The Institute of Cancer Research, London have developed breakthrough blood tests that could revolutionize breast cancer (search) treatment by accurately identifying cancer subtypes and predicting treatment response without the need for invasive tissue biopsies. The findings, presented at the San Antonio Breast Cancer Symposium, represent a significant advance toward personalized cancer care.
Novel Blood Test Identifies Breast Cancer Subtypes
The first innovation, called the Breast Circulating Methylation Assay (BCMA), analyzes circulating tumor DNA (ctDNA) released into the bloodstream by cancer cells. Using machine learning, scientists designed the test to detect markers specific to each major breast cancer (search) type, including estrogen receptor (search) positive or negative (ER+/-), human epidermal growth factor receptor 2 positive or negative (HER2 (search)+/-), and triple negative breast cancer (search).
In a study funded by Breast Cancer Now (search), Wellcome Trust, and Cancer Research UK, researchers analyzed 191 blood samples from 86 patients. The BCMA test demonstrated nearly 90% accuracy at identifying when breast cancers switched subtypes, which occurs in approximately 20% of advanced tumors and represents a major source of treatment failure.
"Our test detects unique patterns in the tumour DNA circulating in a patient's blood to pinpoint the exact breast cancer (search) type," said Dr. Nida Pasha, Clinical Research Fellow at The Institute of Cancer Research and first author of the study. "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."
Expanding Treatment Options Through Blood Analysis
The research revealed that in 8% of samples, while tissue biopsies showed cancer had switched from one type to another, the blood test detected both cancer types simultaneously. This finding suggests patients could benefit from combination therapies targeting multiple cancer subtypes, including aromatase inhibitors (search) for ER+ breast cancers and targeted drugs for triple negative breast cancer (search) such as sacituzumab govitecan.
Additionally, 29% of tissue samples classified as HER2 (search)- showed as HER2+ in the blood test, indicating that more patients may benefit from HER2-targeted therapies than currently receive them.
Predicting Treatment Response with Circulating Tumor DNA
A separate study by the same research team demonstrated that measuring ctDNA levels can predict treatment response in advanced breast cancer (search) patients. The test analyzed blood samples from 167 patients split into two groups based on their cancer characteristics and mutations.
For patients with triple negative breast cancer (search) receiving combination therapy with PARP (search) inhibitor olaparib and ATR inhibitor ceralasertib, those with low ctDNA levels before treatment began experienced significantly longer progression-free survival of 10.2 months compared to 4.4 months for those with higher levels. The response rate was 40% for patients with low ctDNA levels versus 9.7% for those with higher levels.
"By analysing circulating tumour DNA in blood samples from patients with advanced breast cancer (search), we identified a clear link between these levels, both at the start and after one cycle of treatment, and how well patients responded to therapy," said Dr. Iseult Browne, clinical research fellow at the ICR and first author of the treatment response study.
Early Monitoring Shows Promise
The research demonstrated that ctDNA levels measured after just four weeks of treatment provided valuable prognostic information. Patients whose ctDNA became undetectable after one treatment cycle had substantially better outcomes, with cancer controlled for 10.6 months compared to 3.5 months for those with persistent detectable ctDNA.
"Knowing this at the earliest stage – in this case, at the start of treatment, or after just four weeks – means that we can avoid giving patients drugs that won't work and provide them with alternatives before their cancer has a chance to grow," Browne explained.
Clinical Implications and Future Directions
Professor Nicholas Turner, Professor of Molecular Oncology at The Institute of Cancer Research and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust, emphasized the clinical significance of these developments. "Treating breast cancer (search) 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."
The technology's potential extends beyond breast cancer (search). "The technology behind this test isn't limited to breast cancer – it could be applied across many cancer types," Pasha noted. "I'm excited about a future where non-invasive blood tests like this could become the norm, guiding many more cancer treatment decisions."
Professor Kristian Helin, Chief Executive of The Institute of Cancer Research, described the advancement as "a step towards a future of cancer care that is smarter, faster and kinder." With approximately 11,500 women dying from breast cancer (search) annually in the UK alone, these innovations represent crucial progress in addressing an urgent medical need.
The research teams are now planning prospective clinical trials to evaluate whether adapting treatment based on these blood test results improves patient outcomes, potentially transforming the standard of care for breast cancer (search) patients worldwide.