Find out about retinoblastoma, how it develops and what the symptoms can be.
What it is
Retinoblastoma is a rare type of eye cancer.
- 'retino' means from the retina
- 'blast' means cells in early development
- 'oma’ means a group of cells, or a tumour
One eye can be affected, which is called unilateral retinoblastoma. Bilateral retinoblastoma is when both eyes are affected.
Who gets retinoblastoma
Retinoblastoma most commonly affects children under the age of 5. Around 45 children are diagnosed with retinoblastoma in the UK every year. Although this can be very distressing and frightening for the child and their parents, more than 9 out of 10 children (90%) are cured.
Children with both eyes affected are usually diagnosed in the first year of life. Those with one eye affected tend to be diagnosed a bit later, often between 2 and 3 years.
Causes and screening
Some children are born with a change (mutation) in the retinoblastoma gene that they inherited from one of their parents. Or this gene change happened during the very early stages of their development in the womb. This gene is known as the RB1 gene.
About 4 out of 10 children diagnosed (about 40%) have this heritable type, which often affects both eyes. Retinoblastoma tends to develop in just one eye in children who do not have this heritable type.
We don't know what causes the remaining 60% of retinoblastomas. But these non inherited types nearly always only affect one eye.
Children who have a parent or brother or sister who had retinoblastoma should be checked for retinoblastoma. They usually have screening from birth to the age of 3 years. This involves regular eye examinations under a general anaesthetic (so your child is asleep). How often and how long a child has screening for depends on their level of risk.
Some children may also have a blood test to test for the RB1 gene. This is only possible if the family member who has had retinoblastoma can be tested first.
Talk to your GP if you have a family history of retinoblastoma. They can refer your child to one of the specialist retinoblastoma centres. Your child is unlikely to need screening if a more distant relative, such as a cousin, has retinoblastoma. But the retinoblastoma centre can explain which of the family need screening.
To understand how retinoblastoma develops, it helps to know a bit about the eyes and how they work. There are 3 main parts to the eye:
- the globe (eyeball)
- the orbit
- the accessory structures (or adnexal structures) including the tear glands and eyelid.
The eyeball is filled with a jelly-like substance called vitreous humour. It has a lens at the front. The lens is covered by the coloured part of the eye, called the iris.
The lens and iris focus the incoming light onto the back part of the eye, called the retina. The retina is like the film in the camera. When light hits the retina it transmits a message to the brain via the optic nerve. This allows us to see.
How retinoblastoma develops
Retinoblastoma is a cancer of the retina. When a baby is growing in the womb, the eyes are one of the first things to develop. In the very early stages the eyes have cells called retinoblasts that grow very fast. Later, they stop growing and develop into mature retinal cells that can detect light.
Very rarely, the immature retinoblasts continue to grow very fast and do not turn into mature retinal cells. Instead, they grow out of control and develop into a cancerous tumour called retinoblastoma.
If the tumour is not treated, the cells continue to grow and the cancer fills most of the eyeball. It can also spread to other parts of the eye and begin to block the flow of fluid inside the eye. This leads to a build up of pressure and can cause loss of vision.
Most retinoblastomas are found early and successfully treated before they spread outside the eyeball. If they do spread, they can go to anywhere in the body including the brain, bones and lymph nodes. They can be difficult to treat once they have spread.
Most children with retinoblastoma seem well. But two common signs that parents first notice in their child are that:
- the pupil looks odd
- they have a squint
The pupil might look white, like a cat's eye that is reflecting light. Sometimes this is noticed on photos when a flash is used and the pupil appears white rather than the typical red colour. The child might not be seeing as well. Or the eye might be red and inflamed. Children do not usually complain of any pain.
In a very few cases, a child who is not gaining weight or developing normally might be referred to a specialist children's doctor (paediatrician). During their investigations, the abnormal retinoblastoma gene shows up in a blood test.
Urgent referral to a specialist
A GP should refer your child to an eye specialist if the pupil of the eye looks white instead of black. Your child should see this specialist within 2 weeks of the referral.
The stage of a cancer tells you how big it is and whether it has spread. How retinoblastoma is treated depends on the stage of the tumour.
Retinoblastoma has 2 main stages:
The cancer is entirely within the eye and has not spread.Your child's specialist puts the tumour more accurately into one of several more accurate subgroups (A to E) depending on the size and position of the tumour in the eye.
Most children are diagnosed with this localised disease. More than 9 out of 10 of these children (90%) are cured.
The tumour has spread beyond the eye and into the tissues surrounding it. It might have spread to another part of the body.
There are different treatments available for retinoblastoma.
Smaller tumours will need local treatment. That is, treatment just to the eye itself. Larger tumours can be treated with chemotherapy, radiotherapy or surgery.