Researchers have developed a new ‘liquid biopsy’ blood test to diagnose brain tumours, which could reduce the need for invasive procedures.
Diagnosis of brain tumours has relied on testing tissue samples obtained during surgery but there are many different types of brain tumour which cannot be easily differentiated using current techniques and accurately diagnosing them is challenging.
A non-invasive and convenient diagnostic test for brain tumours (such as a blood test) would transform patient care.
Such a test would make it possible to diagnose brain tumours where surgery is not needed or where the risk of surgery outweighs the benefit. Where surgery is needed, an advance diagnosis would guide surgical decisions.
Researchers have been trying for years to develop a convenient diagnostic test using biological fluid from patients, such as blood (a ‘liquid biopsy’).
But what could blood tell us about brain tumours anyway? New research suggests the answer may lie in brain tumour DNA (the genetic code-book for building brain tumour cells) found circulating around the body in the blood.
Until now, it has been challenging to measure the small amount of tumour DNA circulating in the blood and to detect the relatively few number of genetic differences between the DNA of healthy cells and tumour DNA.
However, researchers have now developed a new technique called ‘cell-free methylated DNA immunoprecipitation and high-throughput sequencing’. This test analyses a specific chemical aspect of the tumour DNA called a ‘methylation profile’.
Each type of brain tumour has a different methylation profile, so the specific profile obtained from a sample indicates the diagnosis.
Researchers used blood samples from patients diagnosed with various types of brain tumours and other cancers, and also healthy ‘controls’ (samples from people with no brain tumour) to test how well the technique can detect and differentiate them.
The results showed that the test can distinguish primary brain tumours (i.e., those that originate in the brain) from other non-brain cancer types that may metastasize to the brain.
It can also accurately discriminate different types of primary brain tumour that may be otherwise indistinguishable using current standard-of-care imaging techniques such as MRI.
The test has the potential to change clinical practice for the diagnosis and management of brain tumours but further research is needed to validate and explore the method more fully.
The finding was published in the journal Nature Medicine yesterday.