What is retinoblastoma?

Retinoblastoma is a rare type of eye cancer. It starts in the retina, the inner layer in the back of the eye. 

• 'retino' means from the retina, the inner layer in the back of the eye

• 'blast' means cells in an early stage of development

• 'oma’ means a group of cells, or a tumour

Retinoblastoma in one eye is called unilateral retinoblastoma. Bilateral retinoblastoma means it is in both eyes.

Who gets retinoblastoma?

Retinoblastoma mostly affects children under the age of 5. Doctors diagnose around 40 to 50 children with retinoblastoma in the UK every year.

Children with retinoblastoma in both eyes are usually diagnosed in the first year of life. Those with retinoblastoma in one eye tend to be diagnosed a bit later, around 2 years.

A diagnosis of retinoblastoma can be very distressing and frightening for the child and their parents. But it has the highest survival of any children’s cancer in the UK. Almost 99 to 100 out of every 100 children (99 to 100%) survive for 5 years or more after they are diagnosed.

Causes of retinoblastoma

Some children are born with a change (mutation) in the retinoblastoma gene . They may inherited this 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 40 out of 100 children diagnosed (about 40%) have this heritable (genetic ) type. It often affects both eyes. Heritable retinoblastoma also tends to have more than one cancer in one or both eyes.

The rest, 60 out of every 100 retinoblastomas (60%), are the non heritable (non genetic) type. These usually affect only one eye. In these, the mutation in the RB1 gene occurs later in development. It only affects a single cell in the retina to cause a retinoblastoma.

Screening for retinoblastoma

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 needs checking?

Doctors should check your child to see if they have a close relative who has or has had retinoblastoma. A close relative includes a parent, brother or sister. This involves:

• a blood sample taken during pregnancy. This is from the arm of a mother with the heritable form of retinoblastoma. The test is called Non-Invasive Prenatal Diagnosis (NIPD)
• 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
• a blood test for some children 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 in the UK. They are the:

• Royal London Hospital
• Birmingham Children’s Hospital

Your child is unlikely to need screening if a more distant relative, such as a cousin, has retinoblastoma. The retinoblastoma centre can explain which family members 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 has three layers sandwiched together:

• the outer white fibrous layer, the sclera
• the middle blood rich layer, the choroid
• the inner coloured (pigmented) layer, the retina

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 through the pupil onto the back part of the eye, which is 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 cancer called retinoblastoma.

If the cancer 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.

Doctors find most retinoblastomas early. They are successfully treated before they spread outside the eyeball. If they do spread, they can go anywhere in the body, including the brain, bones, and lymph nodes. Once they have spread, they can be difficult to treat.

Symptoms of retinoblastoma

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 reflecting light. This is sometimes noticed in photos when a flash is used. 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 very few cases, a child might be referred to a specialist children's doctor (paediatrician) because they are:

• not gaining weight
• developing normally

During their tests, the abnormal retinoblastoma gene usually 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 for how quickly children will see a specialist. In England and Wales, 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 and Northern Ireland. But wherever your child lives, a specialist will see them as quickly as possible.  

Getting diagnosed with retinoblastoma

Your child will need several 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 is used to helping children have these tests. They will do everything they can to prepare them and you. For some types of tests, your child might need to be drowsy or asleep. They have sedation to be drowsy and a general anaesthetic to be asleep.

Some of the tests for retinoblastoma include:

• examination of the eye using a light and magnifying glass (ophthalmoscopy)

• ultrasound of the eye. The doctor applies gel over the outside of your child’s eyelid and glides a probe over it. The probe uses sound 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 parts of their body, such as the kidneys, are working

Stages of retinoblastoma

The stage of a cancer tells you how big it is and whether it has spread. How doctors treat retinoblastoma depends on the stage of the cancer.

 Doctors often divide retinoblastomas into 2 main groups:

Intraocular retinoblastoma 

The cancer is only within the eye and has not spread. Your child's specialist puts the cancer into one of several groups. They name them from A to E. Cancers in group A are very low risk. Those in group E are the highest risk group.

Doctors diagnose most children with intraocular retinoblastoma. 

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 for retinoblastoma

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