Scientists are making strides in developing liquid biopsies for brain tumors by detecting tumor DNA in the fluid from around the brain and spine.
Liquid biopsies are fluid samples from patients, for example from the blood or urine, which provide a less invasive way to monitor disease compared to tumor biopsies. A less intrusive test could be hugely beneficial for brain tumors where collecting samples can be difficult and risky for patients.
Scientists at the Cancer Research UK Cambridge Institute analyzed cerebrospinal fluid (CSF) - which bathes the brain and spinal cord - in 13 patients with a type of brain tumor called a glioma. They detected tumor DNA in five (39%) of the patients and their findings are published in EMBO Molecular Medicine.
Researchers used a cheap and widely available technique called shallow whole-genome sequencing to detect brain tumor DNA - they looked for large genetic changes, such as genes being duplicated or lost.
For the first time, the researchers identified tumor 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 tumor DNA, potentially increasing the detection rate.
In one patient, multiple tissue samples from their brain tumor 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 tumors.
Dr Florent Mouliere, co-first author, who conducted the work as a scientist at the Cancer Research UK Cambridge Institute, said: "Liquid biopsies are showing great promise for a number of cancer types, but tests for brain tumors have lagged behind due to the low levels of tumor DNA found in body fluids, in particular the blood.
"Our work shows that a cheap, easily available technique can be used to analyse tumor DNA in cerebrospinal fluid. In the future, we envisage that this technique could be used to identify patients who may benefit from further tests that could help monitor their disease, opening up more tailored treatment approaches."
Around 11,400 people are diagnosed with brain tumors in the UK every year and only 14% of people will survive their disease for a decade or more. That's why Cancer Research UK has made brain tumor research one of its priorities, spending around £25 million over the next five years.
Professor Charles Swanton, Cancer Research UK's Chief Clinician, said: "Survival for brain tumors remains low and there is an urgent need for research like this to identify strategies to better manage these complex diseases. This study lays important groundwork that brings the possibility of liquid biopsies for this hard to treat disease one step closer.
"The researchers will now need to expand this work into larger numbers of patients and find out whether this approach could have applications in the clinic, such as indicating whether a patient's treatment is working."