What is Retinoblastoma
Retinoblastoma is a rare form of eye cancer and, affects approximately 1 in 15,000 live births, but it is the most common inherited childhood malignancy.
It is most commonly diagnosed in children under the age of five, although it can affect children up to 8 years of age, for as long as the eyes are still growing.
Retinoblastoma is a form of rapidly growing tumour that occurs in the retina. This is the light-sensitive lining of the eye.
Retinoblastoma can occur in two forms:
•a non-heritable form where there's a tumour in only one eye (unilateral Retinoblastoma).
•a heritable form where there are often, but not always, tumours in both eyes (bilateral Retinoblastoma)
A child who has hereditary retinoblastoma is at risk for developing pineal tumors in the brain. This is called Pinealoblastoma or trilateral retinoblastoma and usually occurs more than 20 months after retinoblastoma is diagnosed. Regular screening using MRI (magnetic resonance imaging) every 6 months for 5 years may be recommended for a child with hereditary retinoblastoma or with retinoblastoma in one eye and a family history of the disease.
Hereditary retinoblastoma also increases the child's risk of developing other types of cancer such as bone or soft tissue sarcoma or melanoma in later years. Regular follow-up exams are important.
Causes of retinoblastoma
The heritable form of retinoblastoma, which accounts for about two in every five cases, is caused by a genetic abnormality. This means that a gene mutation, in this case found in Chromosom 13, allows the tumour to develop.
The genetic codes found in chromosomes control the way in which cells grow and develop within the body. If a portion of the code is missing or altered (mutation) a cancer may develop.
The defective RB1 gene can be inherited from either parent; in some children, however, the mutation occurs in the early stages of fetal development. It is unknown what causes the gene abnormality; it is most likely to be a random mistake during the copy process which occurs when a cell divides.
Genetic counselling and support is available for families in which a member has retinoblastoma. Not all children of an affected parent will inherit this gene. However, all children born into families with a history of retinoblastoma will be offered blood testing and will usually be checked (screened) for signs of retinoblastoma so that treatment can be started early if a tumour does develop.
Screening usually starts shortly after birth and is repeated every few months for five years. An eye specialist examines the eye while shining a light into it with an ophthalmoscope.
The cause, or causes, of retinoblastoma remain unknown. However, the genetic abnormality in the heritable form of the disease is now well understood. The cause of non-heritable retinoblastoma is unknown.
Signs and symptoms
Some children with retinoblastoma may have no symptoms, but it will be picked up by screening in children of families with a history of the condition.If there's no family history of retinoblastoma, the first sign of the condition is often a white pupil that does not reflect light (leucocoria). This may be detected when a picture of your child is taken using flash photography. The affected eye may look white in the photograph. Some children may have a squint, or if the tumour is large, they may have a painful red eye.
- Other symptoms can include:
- Crossed eyes
- Double vision
- Eyes that do not align
- Eye pain and redness
- Poor vision
- Differing iris colors in each eye
If the cancer has spread, bone pain and other symptoms may occur.
How Retinoblastoma is diagnosed
An eye exam with dilated pupil: An exam of the eye in which the pupil is dilated (opened wider) with medicated eyedrops to allow the doctor to look through the lens and pupil to the retina. The inside of the eye, including the retina and the optic nerve, is examined with a light. Depending on the age of the child, this exam may be done under anesthesia, also known as an EUA, in which an eye specialist (ophthalmologist) will examine your child’s eye while they're asleep. Unlike nearly all other types of cancer, retinoblastomas can be diagnosed just by their appearance, and taking a tissue sample (biopsy) is not usually necessary. Several more EUAs will be carried out to check on the progress of treatment.
Once a retinoblastoma is diagnosed, other tests may be done to check the exact position and size of the tumour, and whether it has begun to spread into surrounding structures. This is known as staging and can include:
- An ultrasound scan. This is a painless scan that uses sound waves to examine the eye and the surrounding area.
- An MRI (magnetic resonance imaging). A scan which gives a series of detailed images that show the structures of the eye and brain.
- A lumbar puncture. This is used to examine some of the fluid from around the brain and spinal cord (cerebrospinal fluid) to see if any tumour cells are present.
- A bone marrow sample. This may be taken to check if there has been any spread of the cancer to the bone marrow.
- A bone scan. This is necessary in some children so that doctors can look more closely for signs of any spread to the bones.
- A blood test for genetic testing for the Rb gene. Results of this test can take some months.
Staging
The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site in the body. Knowing the particular type and the stage of the cancer helps the doctors to decide on the most appropriate treatment.
The following staging system is commonly used for retinoblastoma:
Intraocular retinoblastoma
There is cancer in one, or both, eyes but it has not begun to spread to other parts of the eye or into the tissues surrounding the eye. This stage is sometimes sub-divided into five grades (A–E) depending on the size and position of the tumour and the extent of any damage to the eye. It gives the doctors more information to help them plan appropriate treatment.Extraocular retinoblastoma
The cancer has spread beyond the eye and into the tissue surrounding it or to other parts of the body.If the cancer comes back after initial treatment, it's known as recurrent cancer. It may come back in the eye, the tissue surrounding the eye, or in other parts of the body.
Treatment
The treatment depends on the number, position and size of the tumours in the eye. The aim of treatment is firstly to get rid of the cancer and secondly to try to keep the sight in the eye. Depending on the treatment, some children may lose some of their sight.
Smaller tumours
For smaller tumours, treatment is given to the eye itself (local therapy) by one of the following methods:
Cryotherapy
This is used to freeze the tumours. More than one session may be necessary, in which case they are usually done at monthly intervals.Laser therapy
A laser is used to heat the tumour. Two or three sessions may be needed at monthly intervals.Plaque
For slightly larger tumours, and tumours that have not been successfully treated using other methods, a small radioactive disc can be stitched over the tumour on the outside of the eye. The disc needs to stay in place for up to four days. The radiation destroys the cancer cells.Thermotherapy
This process uses heat to destroy the cancer cells and may be combined with chemotherapy or radiotherapy, as heat can improve the effectiveness of these treatments. The heat is produced by a laser, which is directed at the tumour.Larger tumours
These can be treated in a number of ways, including:
Chemotherapy
Chemotherapy| is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. It may be given before the local treatments mentioned above to help shrink the tumour. This can make the treatment more successful. Chemotherapy can also be used if the cancer has spread to other parts of the body, or if it is thought that there is a significant risk that it will do so.Surgery
If the tumour is very large and the vision in the eye is lost, the eye is likely to be removed|. This is called enucleation. An artificial eye (prosthesis) is then fitted.Radiotherapy
External beam radiotherapy| can be given to the whole eye. Radiotherapy treats cancer by using high-energy rays from a machine to destroy the cancer cells while doing as little harm as possible to normal cells, although there will be some effect on the surrounding tissue. Radiotherapy for retinoblastoma is usually used in situations when other treatments have not been successful.Expectations (prognosis)
If the cancer has not spread beyond the eye, almost all patients can be cured. A cure, however, may require aggressive treatment and even removal of the eye in order to be successful.If the cancer has spread beyond the eye, the likelihood of a cure is lower and depends on how the tumor has spread.
Complications
Blindness can occur in the affected eye. The tumor can spread to the eye socket through the optic nerve. It may also spread to the: brain, lungs and bones.Follow-up
At least 9 out of every 10 children with retinoblastoma are cured. Following treatment|, the eye specialist will frequently examine your child’s eye under anaesthetic to check that the cancer has not come back. Follow-up is usually in a clinic for childhood cancers, called a paediatric oncology clinic.If the retinoblastoma is the heritable form, your child will be given genetic counselling when they are old enough to understand it.
If you have specific concerns about your child’s condition and treatment,
it is best to discuss them with your child’s doctor, who knows the situation in detail.
