Retinoblastoma is a rare type of eye cancer that begins in the retina, the light-sensitive area in the back of the eye. Retinoblastoma occurs when retinal cells develop genetic mutations causing the cells to continue to grow and multiply uncontrollably. Tumors are the result of this accumulative mass of cells. It most commonly affects young children, typically before the age of 5. In most cases it only affects one eye but about one out of three children develop cancer in both eyes. Although most children are born with retinoblastoma, some are diagnosed at birth. After treatment, many go on and maintain good vision; but if not treated quickly, cancer can spread to other parts of the body and become life threatening. There are hereditary as well as non hereditary forms of Retinoblastoma.
Unilateral Retinoblastoma is the non- hereditary form of this cancer that typically only affects one eye with one tumor. In non-hereditary form, there is no family history of the cancer and the affected individual is born with two normal copies of the retinoblastoma gene, RB1. Nevertheless in early childhood, both copies of the RB1 gene acquire mutations. People with non-hereditary retinoblastoma do not risk of passing the RB1 gene to their offspring.
Hereditary retinoblastoma is inherited in an autosomal dominant pattern. Children with hereditary retinoblastoma generally have multiple tumors most likely to develop in both eyes. Inherited retinoblastoma is usually due to transmission of the RB1 mutation, generally followed by an acquired mutation. Children with hereditary retinoblastoma in one eye have a chance of developing it in the other eye, and therefore require regular checkups. A person with hereditary retinoblastoma may pass the altered copy of the RB1 gene to their offspring but doesn’t mean cancer is inevitable. In order for the cancer to arise, a mutation must take place in the other copy of the RB1 gene.
- Cytogenetic Location: 13q14.2
- Molecular Location on chromosome 13 between base pairs 48,877,882 to 49,056,025.
- The RB1 gene is located on the long q arm of chromosome 13 at position 14.2
Characteristics of the Disease
• Leucocoria- White pupil
• Eye redness
• Eye swelling
• Eye pain
• Cross eye
• Blurred vision
• Eyes unable to move or focus
• Enlarged/Dilated pupils
Stages of retinoblastoma:
1. Intraocular retinoblastoma- The early stage of retinoblastoma that can either affect one or both eyes and has not spread outside the eye.
2. Extraocular retinoblastoma- Cancer has spread outside of the eye or to other parts of the body.
3. Recurrent retinoblastoma- Cancer that has come back or spread after being treated.
• Photocoagulation- A laser kills the blood vessel that feed on the tumor.
• Cryotherapy- Low temperatures used to kill caner cells.
• Chemotherapy- Cancer killing medications given to kill or slow the growth of cancer cells. Given intravenously, orally or in injected into fluid surrounding brain and spinal cord.
• Radiation therapy- Using X-ray to kill cancer cells internally or externally. Radioactive material is placed inside or near tumor. Side effects can occur such as cataracts, chronic dry eye, and deformed appearance due to abnormal growth of bones around face.
• Enucleation- Surgery to remove the eye.
Unfortunately children with hereditary retinoblastoma are at a high risk for recurrence of the cancer and 70% chance within 30 years of developing a second cancer.
Mutation involves deletion in the region of chromosome 13 which contains RB1.
- In retinoblastoma, gene RB1 is lost from chromosome 13. RB1 gene provides instructions to make protein RB. pRB’s function is to normalizes cell growth, control cell division and prevents other proteins from triggering DNA replication. Retinal cells that lack a functional pRB divide uncontrollably and cause cancerous tumors.
- The pRB is inactivated by deletion and nonsense mutation. Studies suggest that 40% of RB1 gene is repeated and gather in sixteen spots that include twelve nonsense, two missense and three splicing mutations.
- Many genetic testing options are available that can modify the risks and predict if a child will develop the cancer.
- Molecular genetic testing performed involve study of the tumor that has been surgically removed, or enucleated eye of the patient together with a blood sample
- Family members are also screened and observed to see who is at an increased risk.
- Early recognition of retinoblastoma may allow for timely intervention and exams can begin at an early stage when tumors are small and cure is possible.
Other relevant information
Children that are affected by retinoblastoma also have intellectual disability, slow growth, and distinct facial features. Although RB generally does not spread, patients with hereditary form are at risk of developing tumors beyond the eye. Retinoblastoma can spread to the brain through the optic nerve as well as other organs in the body but early diagnosis and treatment can reduce morbidity of RB and related tumors. Retinoblastoma treatments have a 90% success rate!
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