Scientists have found that deadly childhood brain tumours are actually 10 different diseases that should each be diagnosed and treated based on their specific genetic faults.

The major new study has important implications for treatment, since personalising care for each type of brain tumour is likely to be much more effective than grouping them all together as one.

A team at The Institute of Cancer Research, London, found stark differences among children’s ‘high grade’ brain tumours, or gliomas, and that they could be split into at least 10 different cancers.

Some types should be far more treatable than others using drugs under development or already on the market.

The study, published in the journal Cancer Cell, is the world’s largest of these aggressive childhood brain cancers and should lead to more accurate diagnostic tests to ensure each child receives the best possible treatment. Many of the children had mutations in their tumours that can be targeted by existing drugs approved for adult cancers, demonstrating the benefit of testing children for genetic mutations in their tumours at the point of diagnosis.

Researchers gathered genetic data from 910 cases from 20 previously published analyses and 157 new cases, from children or young adults up to the age of 30 with high-grade glioblastoma or diffuse intrinsic pontine glioma (DIPG).

Although rare, these are the biggest cause of cancer-related death in people under 19 years of age because survival rates are so poor – children with these tumours are only expected to live an average of 9-15 months.

It is therefore vital to find out more about their biology, what makes them so deadly, and how they might be treated.

The tumours could be split into different subtypes based on different characteristics, such as age at diagnosis, area of the brain, the number of genetic mutations and – crucially – errors in key genes that drive the disease. One of the striking findings from the study was that while some children’s tumours were driven by a single genetic error in which two genes were fused together, others had tens of thousands of genetic errors – among the highest number of mutations in any human cancer.

Tumours with mutations in a gene called BRAF were found to be much less aggressive than some of the other cancers, and actually shouldn’t be classified as ‘high grade’ at all. These tumours could be susceptible to several adult cancer drugs that target BRAF mutations.

Scientists at the ICR, a research institute and charity, found mutations in common cancer genes such as PDGFRA, KIT, MYCN, EGFR, CDK6, and genes involved in DNA repair – all of which can be targeted by existing drugs.

They also uncovered numerous new potential therapeutic targets within each subtype, such as the gene TOP3A – a gene involved in DNA replication – in tumours with a specific type of histone mutations called H3.3K27M.

Three of the subtypes were distinguished by the presence or absence of different mutations in genes that produce histones – proteins that DNA is wrapped around to pack it tightly into cells. Histones are also involved in turning off and on certain genes – a role that can be very important in cancer.

Although there are currently no drugs that can target histone mutations, there are some in development and the presence or absence of these mutations gave clues about how aggressive the cancer is, and could point to future approaches to treatment.

The data produced by this study is now considered the definitive dataset on these cancers, and will be made available on a public data portal so the research community can use it to develop new tests and treatments. Study leader Professor Chris Jones, Professor of Childhood Brain Tumour Biology at the ICR, said: “Our study uncovered a wealth of new information about children’s brain cancers. We found that tumours that have his