What is retinoblastoma?
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
Retinoblastoma affecting one eye 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 36 children are diagnosed with retinoblastoma in England every year.
Children with retinoblastoma in both eyes 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.
Although the diagnosis can be very distressing and frightening for the child and their parents it has the highest survival of any children’s cancer in England. Almost all children (99-100%) survive for 5 years or more after they are diagnosed.
Causes and screening
Some children are born with a change (mutation) in the retinoblastoma 
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. Heritable retinoblastoma also tends to have more than one tumour in one or both eyes.
The remaining 60% of retinoblastomas are non heritable (non genetic) type. These nearly always affect only one eye. In these the mutation in the RB1 gene occurs later in development and only affects a single cell in the retina to cause a retinoblastoma.
Screening
The aim of screening for retinoblastoma is to spot cancer at an early stage. This means treatment is more likely to be successful and improve your child’s chance of survival.
Who should be checked?
Your child should be checked if they have a close relative such as a parent, brother or sister who has or has had retinoblastoma. This involves regular eye examinations under a general anaesthetic (so your child is asleep). How often and how long your child has screening for depends on their level of risk. They usually have regular screening from birth to the age of 5 years. This may vary between different retinoblastoma centres.
Some children may also have a blood test to check for the RB1 gene. This is only possible if the family member who has had retinoblastoma can be tested first.
If your child’s relative does not have the mutation, they won’t need screening for retinoblastoma.
Talk to your GP if you have a family history of retinoblastoma. They can refer your child to one of the two specialist retinoblastoma centres (Royal London Hospital or Birmingham Children’s Hospital). 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.
The eye
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, which is the bony hollow structure that holds the eye
- the accessory structures (or adnexal structures). These protect and support the working of the eye such as the tear glands and eyelids.
The eyeball is filled with a jelly-like substance called vitreous humour. It has a lens at the front. In front of the lens is 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 . They can be difficult to treat once they have spread.
Symptoms
Most children with retinoblastoma seem well. But two common signs that parents first notice in their child are that:
- they have a white glow or white reflection in the centre of their eye (pupil) - this is also known as leukocoria
- their eyes are not looking in the same direction (a squint) - also known as strabismus
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.
Other less common symptoms might include:
- you or the school noticing your child can’t see properly
- inflammation and reddening of their eye
- uncontrollable movement of their eye from side to side (nystagmus)
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
There are guidelines to help GPs know when to refer a child urgently to see a specialist. This is to help investigate their symptoms further and help rule out cancer.
Some of the UK nations have targets around how quickly they’ll be seen. In England an urgent referral means that your child should see a specialist within 2 weeks.
This 2 week time frame is not part of the waiting time targets for Scotland, Wales and Northern Ireland. But wherever your child lives, they will be seen as quickly as possible.
Getting diagnosed
Your child will need a number of tests if their doctor suspects they have retinoblastoma. These aren’t generally painful. But your child will have to keep still for some of them.
The team caring for your child are used to helping children have these tests. They will do everything they can to prepare them, and you. For some types of test, your child might need to be drowsy () or asleep ().
Some of the tests for retinoblastoma include:
- examination of the eye using a light and magnifying glass (ophthalmoscopy)
- ultrasound of the eye. A wand like probe glides over gel that is placed on the outside of your child’s eyelid. The probe uses sounds waves to form a picture of the eye and its structures on the screen
- magnetic resonance imaging (MRI scan). The MRI scan creates a picture using magnetism and radio waves
- testing for changes to your child’s genes (genetic testing). This is either a blood test or they use a sample of tissue from the eye. Your child might also have other blood tests to check how well their parts of their body are working, such as the kidneys
Stages
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:
Intraocular retinoblastoma
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. These groups are labelled A to E. A being the very low risk group, E being the highest risk group.
Most children are diagnosed with intraocular disease.
Extraocular retinoblastoma
The cancer has spread beyond the eye and into the tissues surrounding it. It might have spread to another part of the body. In the UK this is rare.
Treatment
There are different treatments available for retinoblastoma. The treatment your child has will depend on several factors such as their stage and risk group.
Treatment for retinoblastoma might include one or more of the following:
- freezing therapy (cryotherapy)
- laser therapy
- chemotherapy
- radiotherapy
- surgery
