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Scientists have found that deadly childhood brain tumors 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 personalizing care for each type of brain tumor 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 tumors, 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 today in 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 tumors that can be targeted by existing drugs approved for adult cancers, demonstrating the benefit of testing children for genetic mutations in their tumors 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 tumors 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 tumors 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 tumors 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.

Tumors 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 tumors 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 tumors with a specific type of histone mutation 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.

"Our study uncovered a wealth of new information about children's brain cancers. We found that tumors that have historically been lumped together under one diagnosis are in fact comprised of many, remarkably different, diseases,” said study leader Chris Jones, professor of childhood brain tumor biology at The Institute of Cancer Research, London.

"Treating cancer based only on what we see down the microscope simply isn't good enough any more. We need to start thinking about these as completely different cancers and diagnosing and treating them based on their genetic faults. It's exciting that several types look like they could be clearly treatable using either existing drugs on the market or other treatments under development.

"We worked with colleagues across the world to gather enough data on these rare cancers to understand better what makes them so aggressive, and what mutations occur that might make them susceptible to different treatments."

"A diagnosis with one of these high-grade brain tumors in children is devastating for families. We desperately needed to understand the biology of the diseases better if we are ever to find ways of treating them effectively. This important study is a vital step forward,” said Paul Workman, chief executive of The Institute of Cancer Research, London.

"We really need to get much better at making modern, targeted cancer treatments available for children, which means improving access to genetic testing and changing regulations so more drugs get tested in pediatric clinical trials."

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