A new type of retinoblastoma, which is a rapidly developing eye cancer that affects very young babies, has been discovered. This finding can immediately change clinical practice and optimize care for these children.
The finding is a breakthrough in recognizing that a single cancer gene, known as an oncogene, drives an aggressive retinoblastoma that starts long before birth in families with no history of the disease. This was explained by surgeon Brenda Gallie, FRCPC, MD, of the Princess Margaret Cancer Centre in Toronto, Canada. Gallie led the international team that used collaborations from several clinical labs to conduct the study.
This study demonstrates that molecular diagnostics can identify novel malignant diseases that elude traditional microscopic study of tissue. The researchers analyzed more than 1,000 primary unilateral nonfamilial retinoblastoma tumors to validate oncogene-driven retinoblastoma.
“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 tumor 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 tumors. When we remove the eye with a large tumor 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 personalized cancer medicine for these children and families.”
The oncogene-driven tumors 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. Sometimes Mom really does know best and clinicians should pay close attention.”
Although less than 2% of unilateral retinoblastoma tumors is driven by the oncogene, the early age of onset predicts that approximately one in five babies given a diagnosis at younger than 6 months actually has oncogene-driven retinoblastoma. The finding was published in Lancet Oncology (2013; doi:10.1016/S1470-2045(13)70045-7).
“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 at diagnosis of this new type of retinoblastoma is 4 months.”