Tumours are the leading cause of death for children with cancer. The most common type, medulloblastoma, is diagnosed in about 100 pediatric patients a year in Canada.

Until now, these infants and children have been treated alike with surgery, whole-brain radiation, and aggressive chemotherapy. Despite treatment, 30 to 40 percent die as a result of their primary tumours. A further 30 to 40 percent of the initial survivors develop recurring tumours, which are almost inevitably fatal. And many of the remaining patients are left with neurological, intellectual, and physical disabilities from the treatment’s effects on their developing brains.

Determined to transform the way these children are treated, scientists at the BC Cancer Agency Genome Sciences Centre teamed up with clinicians and researchers at The Hospital for Sick Children in Toronto and 46 cancer centres around the world to launch the MAGIC (Medulloblastoma Advanced Genomics International Consortium) project. Together they gathered more than 1,000 pediatric medulloblastoma samples.

Using cutting-edge technology, the Canadian scientists analyzed the entire genomes of primary tumours and matched recurrences. They confirmed not only that there are four distinct molecular subgroups of medulloblastoma, but that these have clinically significant subsets. They also discovered that the genetic profile of a recurring tumour has little in common with the original tumour.

“This explains why nothing would work on the recurring tumours,” says Dr. Michael Taylor, a pediatric neurosurgeon and scientist at SickKids.By classifying the tumours, clinicians will be able to diagnose and treat future pediatric patients with medulloblastoma with much greater precision — reducing radiation in children with a low-risk type, for example, to preserve their quality of life, while maintaining cure rates.

By identifying specific molecular targets for interventions,the research will also improve clinical trials and support the development of new drug therapies tailored to individual patients.Dr. Taylor co-leads the MAGIC project with Dr. Marco Marra, director of the Genomics Innovation Centre at the BC Cancer Agency Genome Sciences Centre (one of 10 Genomic Innovation Network Nodes across the country funded by Genome Canada), and Dr. David Malkin, senior oncologist at the Hospital for Sick Children.

Understanding the differences in the genetic makeup of these tumours and how the differences affect response to treatment will reduce the large burden of suffering and misery of families whose children may not be receiving the most appropriate treatment. This knowledge is expected to save health-care systems in Canada more than $25 million a year.

August 2014