A breakthrough by scientists could help cure deadly child brain tumours, a new study has claimed.

Researchers have for the first time pinpointed a rearrangement of DNA present in around two-thirds of all cases of the most common brain tumours in five to 19 year olds.

Described as a "significant discovery", the research published in Cancer Research - the journal of the American Association of Cancer Research - could provide leads for creating better treatments and make diagnosis of the disease more accurate.

Professor Peter Collins, who led the research at Cambridge University, said: "If we can diagnose exactly which type of brain tumour a child has as early as possible, the tumour is more likely to be treated successfully. We also hope the findings will mean it is possible to create therapies in the future that block the activity of the fusion gene and halt the growth of tumour cells."

The new study was funded by Cancer Research UK and the Samantha Dickson Brain Tumour Trust, set up in 1996 by Samantha's parents Neil and Angela Dickson, from Dogmersfield, Hampshire. Samantha died of cancer twelve years ago, aged 16.

Around 3,400 people lose their lives to a brain tumour each year but very little is known about the causes and genetics of childhood brain tumours, the second most common type of childhood cancers. Known as Pilocytic astrocytomas, the most common type of such tumours, they affect around 145 children each year in the UK - and around a quarter cannot be successfully treated.

Professor Collins added: "This is the first time a specific genetic link has been made to the majority of pilocytic astrocytomas.

"We found a specific rearrangement of DNA in around two-thirds of all cases of pilocytic astrocytoma. The resulting DNA sequence includes a portion of a gene called BRAF that is known to be mutated in a number of other cancers, and which we think may trigger this disease."

Paul Carbury, chief executive of Samantha Dickson Brain Tumour Trust said: "This world class piece of research has made a major breakthrough."

Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "It's often more difficult to treat brain tumours successfully because of the sensitive position of the tumour. Any discovery that adds to our understanding of the cancer pathways that cause these tumours to form is exciting news, and we think this important finding will be vital in guiding future research."