Rare mutations in advanced breast cancer can be identified through a simple blood test, in what clinicians have described as a “huge step”, it was announced last night.
Cancer Research UK scientists undertook a study as part of the plasmaMATCH clinical trial and detected mutations in the DNA from tumours in the bloodstream.
They also found specific weaknesses in the breast cancer DNA that could be targeted with drugs.
This suggests that the blood test would provide better guidance for treatment compared to biopsies, they report.
The team, from the Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, presented the results at the 2019 San Antonio Breast Cancer Symposium yesterday (12 December 2019).
The study, undertaken to see if taking a liquid biopsy is quicker and easier than traditional tumour testing, involved the analysis of blood from about 1,000 women whose breast cancer had returned after treatment, or had spread to another part of the body.
The research team wanted to see if a blood test could detect three targetable defects in HER2, ESR1 and AKT1 genes, all of which are known to drive breast cancer.
They examined 142 women with the detectable mutations who were given experimental targeted therapies to attack the specific characteristics of their cancer. The researchers found that the treatments are promising but will undertake further tests in larger clinical trials.
The researchers also checked tissue samples from the patients and found the liquid biopsy had correctly identified the presence or absence of the mutations in more than 95% of cases.
Professor Nicholas Turner, professor of molecular oncology at The Institute of Cancer Research, London, and consultant medical oncologist at The Royal Marsden, said: “The choice of targeted treatment we give to patients is usually based on the mutations found in the original breast tumour. But their cancer can have different mutations after it has moved to other parts of the body.
“We have now confirmed that blood tests can quickly give us a bigger picture of the mutations are present within multiple tumours throughout the body, getting the results back to patients accurately and faster than we could before.
“This is a huge step in terms of making decisions in the clinic, particularly for those women with advanced breast cancer who could quickly be put on new targeted treatments matched to their cancer if it evolves to become drug resistant.”
The researchers believe the blood tests are now reliable enough to be used routinely by doctors, once they have passed regulatory approval.
GS3-06. Turner, N et al. Results from the plasmaMATCH trial: A multiple parallel cohort, multi-centre clinical trial of circulating tumour DNA testing to direct targeted therapies in patients with advanced breast cancer (CRUK/15/010). San Antonio Breast Cancer Symposium 12 December 2019
GS3-07. Kingston, B et al. The genomic landscape of breast cancer based on ctDNA analysis: data from the plasmaMATCH trial. San Antonio Breast Cancer Symposium 12 December 2019
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