Retinoblastoma is an embryonal tumour (arising in primitive developing cells) and, as such, most cases occur in very young children.
Retinoblastoma is one of only a very small number of childhood cancers that is caused by a genetic defect inherited from parents. Around 40 per cent of retinoblastoma cases are of the heritable form.
Retinoblastoma can be either unilateral (one eye, around two thirds of cases), or bilateral (both eyes). All children with bilateral tumours have the heritable disease, whereas only 10 per cent of unilateral cases have the heritable form.
The heritable form of retinoblastoma is now well understood. It occurs as a result of two alterations (called mutations) in the ‘retinoblastoma suppressor gene’ (RB1). The abnormal gene can be passed from a parent to their child, allowing the tumour to develop. Or this alteration can occur spontaneously while the baby is developing in the uterus.
Children with the heritable form have an increased risk of developing other types of cancer later in life.
Genetic counselling and support is available for families in which a member has retinoblastoma. Not all children of an affected parent will inherit the faulty gene but all children born into families with a history of retinoblastoma will be screened regularly during their first five years of life for signs of retinoblastoma so that treatment can be started early if a tumour does develop.
The causes of the non-heritable form of retinoblastoma are not understood.
Around 40 children are diagnosed with retinoblastoma every year in the UK. Almost all of those affected are under five years of age. More than 40 per cent of cases occur within the first year of life.
Most of the bilateral cases – which represent just over a third of cases overall – are diagnosed in the first year of life.
Overall, incidence is similar among males and females but there is a male excess of bilateral retinoblastoma (5:4) and a female excess of unilateral retinoblastoma (6:5).#
Advances in the diagnosis and treatment of retinoblastoma mean that almost every child can be cured. Data for the period 2006 to 2010 show a five year survival rate of 100 per cent.
Unfortunately, however, survival may be at the expense of some or all of the child’s sight.
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