New 'ultra-sensitive' blood test can predict if breast cancer will come back long before scans

An innovative blood test has been developed, capable of predicting the resurgence of breast cancer even before it can be detected on scans.

This ground-breaking advance could allow treatments to be initiated earlier, even before the disease becomes incurable. These ultra-sensitive tests can identify a tumour's DNA traces before a complete relapse, a stage when it is generally more challenging to treat.

The test was found to be 100% accurate at forecasting which patients would face a recurrence of their cancer. Dubbed as a "liquid biopsy", this method utilises whole-genome sequencing in locating genetic defects in the DNA of the patient, a potential indicator of cancer.

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Researchers from London's Institute of Cancer Research (ICR) tested this methodology on 78 early stages breast cancer patients. The test focuses on 1,800 mutations shed by cancer cells into the blood, known as circulating tumour DNA (ctDNA). In 11 women, the ctDNA was discovered and eventually, all their cancers came back.

The other women involved in the study showed no signs of a relapse, reports WalesOnline. Blood samples were collected and analysed at the time of diagnosis, post-surgery, and after chemotherapy sessions.

These tests were then repeated every three months for the next year and every six months for the next five years. On average, the blood test detected cancer 15 months before symptoms appeared or it showed up on scans.

The earliest was 41 months before a scan confirmed the diagnosis, according to the results presented at the American Society of Clinical Oncology conference in Chicago. Detection of the tumour DNA at any point after surgery or during the follow-up period saw patients have a higher risk of future relapse and poorer overall survival.

Lead researcher Dr Isaac Garcia-Murillas, from the ICR, said: "Breast cancer cells can remain in the body after surgery and other treatments but there can be so few of these cells that they are undetectable on follow-up scans."

He added: "These cells can cause breast cancer patients to relapse many years after their initial treatment. Ultra-sensitive blood tests could offer a better approach for the long-term monitoring of patients whose cancer is at high risk of returning."

"Most personalised liquid biopsies currently use whole exome sequencing to identify mutations. But this approach goes one step further and uses whole genome sequencing to identify up to 1,800 mutations in a patient's tumour DNA that could uniquely identify recurrence of the patient's cancer from a blood sample."

"A more sensitive test is very important for this group of early breast cancer patients as they tend to have a very low amount of cancer DNA in their blood. This proof-of-principle retrospective study lays the groundwork for better post-treatment monitoring and potentially life-extending treatment in patients."