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Retinoblastoma

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There are many cancers that affect the body organs, of which retinoblastoma is a common childhood cancer. It is mostly diagnosed in children under the age of 3 years and on rare occasions in adults. Let us learn more about retinoblastoma from the following paragraphs.

What is Retinoblastoma?

Retinoblastoma is a malignant tumor of the eye. In the eye(s), it is specifically originates in the retina, that is, the light-sensitive lining of the eye. The cancer can occur in one eye (unilateral) or affect both eyes, that is, bilateral.

Retinoblastoma is seen in 1 out of every 15,000 live births. About 90% of the cases are detected in children under the age of 5 years. Retinoblastoma is a malignant cancer and therefore, can lead to permanent loss of vision and even life, if not detected and treated early.

Retinoblastoma can be genetic or inherited. This form of retinoblastoma can develop in both eyes or single eye. There is a non-heritable form as well that usually causes tumor in one eye only.

Causes of Retinoblastoma

The eyes develop in the womb in the fetal stage. In the early stages of development, the retinoblasts in the eyes divide to form new cells that make up the retina. There comes a point when the cells stop dividing and develop into a mature retinal cell. It is during this process, in rare occasions, the cells grow out of control. Instead of developing into light detecting retinal cells, they continue to divide and grow, leading to retinoblastoma.

This abnormal divide and growth process occurs due to a mutation in the gene called the retinoblastoma (RB1 or Rb) gene. The Rb gene makes sure the cells do not grow out of control. When a mutation occurs, the gene does not work as it normally would. Depending on the site of mutation on Rb gene, the two forms of retinoblastoma occurs.

Hereditary retinoblastoma is seen in 1 out of 3 retinoblastoma cases. The mutation on Rb gene is present at birth, that is, congenital. This mutation is present in all the cells within the body as well as both retinas. This type of mutation is called as germline mutation.

It is found about 75% children develop this mutation during the early fetal development. The exact cause of this mutation is still unclear. As the cancer cells are present in both the retinas, these children have retinoblastoma of both eyes. Also, such children are at risk of developing other cancers as the mutation is seen in every other cell of the body.

Nonhereditary retinoblastoma is seen in 2 out of 3 cases. The mutation on the gene develops in just one cell of the eye. Thus, the cancer occurs in just one eye of the affected child. The exact cause of this form of retinoblastoma is unknown.

How Does Retinoblastoma Spread?

Untreated retinoblastoma continue to grow and affect most of the cells in the retina and eyes. The vitreous fluid within the eye gets filled with these tumors. When the tumors detach from the retina, they break into smaller tumors. These small tumors are called as vitreous seeds. They float in the vitreous and are very difficult to treat.

These vitreous seeds reach other areas within the eye and spread the cancer. When they block the channels that helps circulate the fluid within the eye, it causes an increase in pressure inside the eye. It leads to glaucoma and loss of vision of the affected eye.

Retinoblastoma can spread into the tissue under the retina, eye socket, optic nerve, brain as well as the bones and bone marrow. Thus, it is very important that the diagnosis of retinoblastoma is made when the tumor is still present in the retina.

Signs and Symptoms of Retinoblastoma

The most common and obvious sign of retinoblastoma is often observed by parents after they observe the eyes of their child under bright light or in a photograph clicked. The child’s pupil(s) has a white color in a color photo. Under dim lights, the pupils tend to have a white glow or glint. This is called as leukocoria or amaurotic cat's eye reflex. When photos are taken using flash, one observes a red-eye effect under normal condition. However, in case of retinoblastoma the eye or eyes shine bright white.

The affected child may also complain of poor or weak vision. One or both eyes turn inward or outward. The child may also suffer from eye pain due to the pressure from the growing tumor within the eye(s).

Diagnosis of Retinoblastoma

Retinoblastoma is diagnosed after carrying out may tests and procedures. The eye is examined by an ophthalmologist after putting the child to sleep under anesthesia. The child is sedated to prevent him/her from moving during the examination. As the appearance of the eye will help prove retinoblastoma, it is not always necessary to conduct a biopsy.

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After retinoblastoma is diagnosed, other tests will be conducted to stage the cancer. This helps the doctor learn about the exact position and size of the tumor. It also helps stage the cancer and determine whether is has spread to other areas of the eye(s). These tests include:

  • Ultrasound scans
  • MRI
  • Lumbar puncture
  • Bone marrow sample
  • Bone scan
  • Blood test for genetic testing of the Rb gene

Treatment of Retinoblastoma

The treatment of retinoblastoma depends on the position, size and number of tumors within the eye. The main aim of treatment is to clear the eye of all tumors and secondly, to save the sight in the eye.

In case of smaller tumors, the doctor will give local therapy, that is, treatment to the eye directly. The child is put under anesthetic when imparting this treatment. The local therapy methods include:

  • Cryotherapy: The tumor cells are frozen to kill them. Once the cells freeze, the substance injected, that is, liquid nitrogen is removed. Then, the cells begin to thaw. This procedure is carried out multiple times during each session that is scheduled over a period of time.
  • Laser therapy: Heat is used to kill the tumor cells. There are many sessions schedule for laser therapy at an interval of 3 to 4 weeks.
  • Plaque: A small, radioactive disc is placed outside the eye. This disc is kept fo 4 days to allow the radiation to kill tumor cells of slightly larger tumors or tumors that are not treated by the above methods.

Larger tumors are treated using chemotherapy and radiotherapy. In case the tumor is very large and has spread to other parts of the eye, surgery is necessary. The eye may have to be removed (enucleation) in order to save the child’s life. After the eyeball is removed, the surgeon will immediately place a plastic or other material ball into the eye socket. This helps the eye muscles that control the eye movement adapt to the implant and continue to move as it would have with the natural eye. Once the healing is complete, the doctor will fit a customize artificial eye in the eye socket.

Prognosis for Retinoblastoma

9 out of 10 affected children are completely cured of retinoblastoma after treatment. Children with hereditary retinoblastoma need genetic counselling when they are old enough to understand. They are prone to developing other types of cancers later on in life. Thus, any changes in the body like lumps or skin color changes should be brought to the notice of their doctor.

It is very difficult as a parent to accept their child is suffering from cancer at such an early age. Also, it becomes more difficult to make the child understand the disease and its complications such as loss of vision. One has to always maintain a positive attitude and support the child through this difficult stage of life that they may find hard to comprehend.

Written by: Saptakee sengupta
Date last updated: April 01, 2015