Scientists are making strides in developing liquid biopsies for brain tumours by detecting tumour DNA in the fluid from around the brain and spine.

The Cancer Research UK team analysed cerebrospinal fluid (CSF) in 13 patients with glioma brain tumours.
They detected tumour DNA in five (39%) of the patients.
The researchers used a cheap and widely available technique called shallow whole-genome sequencing to detect brain tumour DNA. They looked for large genetic changes, such as genes being duplicated or lost.
For the first time, the researchers identified tumour DNA in the CSF by looking at the size of the DNA fragments, which are shorter than those from healthy cells. This provides another way to detect brain tumour DNA, potentially increasing the detection rate.
In one patient, brain tumour tissue samples were compared to their CSF. The genetic changes broadly matched, but the CSF contained changes that were missed in some of the tissue samples, suggesting that CSF samples could reflect the repertoire of genetic alterations found in brain tumours.
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