Scientists have discovered that some childhood bone cancers start growing years before tumours appear and get diagnosed.

Ewing sarcoma is a rare cancer found mainly in bone or soft tissue of young teenagers as they grow, and is the second most commonly diagnosed bone cancer in children and young people. Researchers at the Wellcome Sanger Institute and Hospital for Sick Children (SickKids) discovered large scale rearrangements in Ewing Sarcomas and other children's cancers, and showed that these can take years to form in bone or soft tissue. 

In Ewing sarcoma, two specific genes, EWSR1 and ETS, are fused together. "Many childhood sarcomas are driven by gene fusions, however until now we have not known how or when these key events occur, or whether these processes change at relapse," said Adam Shlien, one of the lead authors, Associate Director at SickKids Hospital. 

"We found dramatic early chromosomal shattering in 42 per cent of Ewing sarcomas, not only fusing two critical genes together, but also disrupting a number of important areas," he added, in the paper reported in the journal Science. 

To understand the genetic events leading to this, the team sequenced and analysed the genomes of 124 tumours. They discovered that in nearly half of the cases, the main gene fusion occurred when the DNA completely rearranged itself, forming complex loops of DNA.

"As an increasing and diverse number of tumour genome sequences become available, we may be able to define further rearrangement processes that underlie fusion genes and thus unravel the causes of fusion-driven human cancers," noted David Malkin, co-leader author, Oncologist, at the SickKids Hospital. "Our goal is to better understand these cancers in an attempt to improve treatment and outcomes," he concluded.