Detecting, as well as treating, brain cancers has historically presented a challenge for researchers and clinicians. Though, with new techniques such as liquid biopsy and advanced sequencing methods, identifying tumors within the brain could become considerably easier. Now, investigators at the Cancer Research UK (CRUK) Cambridge Institute have made considerable progress 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.

Findings from the new study were published today in EMBO Molecular Medicine through an article titled “Detection of cell‐free DNA fragmentation and copy number alterations in cerebrospinal fluid from glioma patients.”

“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,” explains co-lead study investigator Florent Mouliere, Ph.D., who conducted the work as a scientist at the Cancer Research UK Cambridge Institute. “Our work shows that a cheap, easily available technique can be used to analyze 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.”

In the current study, the 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. Amazingly, they were able to detect tumor DNA in five (39%) of the patients in the study.

Subsequently, the researchers used a cheap and widely available technique called shallow whole-genome sequencing to detect brain tumor DNA—the CRUK team looked for large genetic changes, such as genes being duplicated or lost. The researchers were able to identify 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.

Interestingly, 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.

Survival for brain tumors remains low, and there is an urgent need for research like this to identify strategies to manage these complex diseases better. This study lays the important groundwork that brings the possibility of liquid biopsies for this hard to treat disease one step closer,” concludes Chares Swanton, Ph.D., Cancer Research UK’s chief clinician.” 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.”