Scientists have discovered a new type of retinoblastoma, a rapidly developing eye cancer that affects very young babies.
A team of Canadian and international cancer researchers led by Dr Brenda Gallie at the Princess Margaret Cancer Centre, University Health Network (UHN) in Toronto, found that a single cancer gene (an oncogene) drives an aggressive retinoblastoma that starts long before birth in families with no history of the disease.
"This research completely challenges conventional thinking and clinical practice," said Gallie.
"The common type of retinoblastoma is initiated by damage to both copies of the RB1 tumour suppressor gene; the predisposition to this type of retinoblastoma can be inherited, so the other eye of the child and those of infant relatives are at risk to develop tumours," Gallie said.
"When we remove the eye with a large tumour in very young babies and show it is the new oncogene-driven type of retinoblastoma, there is believed to be zero risk for retinoblastoma developing in the other eye or in other infants in the family. This is a major advance in personalised cancer medicine for these children and families," Gallie added.
The oncogene-driven tumours are much larger than those anticipated in children with inherited retinoblastoma at the same age.
"The earliest diagnosis comes when parents observe a white (instead of black) pupil of the eye, and the doctors listen to their observations and understand the urgency of referral," she said in a statement.
Although less than 2 per cent of unilateral retinoblastoma tumours are driven by the oncogene, the early age of onset predicts that about 1 in 5 babies diagnosed under six months of age actually has oncogene-driven retinoblastoma.
"All the babies were completely cured by surgery," said Gallie.
"We've thought for a long time that all retinoblastoma were caused by loss of the retinoblastoma gene. Our study now reveals that's not the whole story: a new type of retinoblastoma, with normal retinoblastoma genes, is instead driven by extra copies of a powerful cancer gene, causing the cancer to grow very rapidly long before birth. The average age of diagnosis is four months," she said.
The study was published in journal Lancet Oncology.
