Retinoblastoma is a rare cancer of the retina (the innermost layer of the eye, located at the back of the eye, that receives light and images necessary for vision). About 250 children will be diagnosed with retinoblastoma this year. It accounts for 3 percent of childhood cancers.
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Retinoblastoma occurs due to mutations in a tumor suppressor gene (called RB1) located on chromosome #13. Two mutations (or gene changes) are necessary to "knock-out" this gene, and cause uncontrolled cell growth. In inherited retinoblastoma (40 percent of the cases), the first mutation is inherited from a parent, while the second occurs during the development of the retina. In sporadic retinoblastoma (60 percent of the cases), both mutations occur during development of the retina. Sporadic means "occurs by chance." Alterations in the RB1 gene have also been found in other tumors, including osteosarcoma and breast cancer.
Most children with inherited retinoblastoma generally have tumors involving both eyes. (In fact, all cases involving both eyes should be considered hereditary). The RB1 gene is an autosomal dominant gene, which means that both males and females are equally affected, and there is a 50/50 chance, with each pregnancy, for a parent to transmit the gene to a child. When a child inherits the gene, there is about a 90 percent chance for the second mutation to occur, resulting in retinoblastoma. This means that some children who inherit the mutation may never get the second mutation, and may, therefore, never develop retinoblastoma. (They can still transmit the gene to their offspring, however, so that their children could develop the disease.)
Consider the following statistics:
- 60 percent to 75 percent of retinoblastoma cases involve one eye (unilateral). Of these, about 15 percent are inherited, and the remaining 85 percent are sporadic.
- 25 percent of retinoblastoma cases are bilateral (both eyes) and hereditary.
- 15 percent of retinoblastoma cases are unilateral (one eye) and hereditary.
Any individual with a positive family history of retinoblastoma may want to seek genetic counseling to identify the specific risks of passing the gene or disease to their children.
The following are the most common symptoms of retinoblastoma. However, each child may experience symptoms differently. Symptoms may include:
- leukocoria - a white light reflex that occurs at certain angles when light is shown into the pupil.
- strabismus (Also called "wandering eye" or "crossed-eyes.") - a misalignment of the eyes; when one or both eyes do not appear to be "looking" in the same direction.
- pain or redness around the eye(s).
- poor vision or change in child's vision
Often the symptoms may not appear if the disease is diagnosed early. The symptoms of retinoblastoma may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
In addition to a complete medical and physical examination, diagnostic procedures for retinoblastoma may include:
- complete eye examination
- fundoscopic examination - with the child under anesthesia, the pupils are dilated so the entire retina can be viewed and examined.
- computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
- magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- blood tests
- tests of the fluid surrounding the tumor
- genetic and/or DNA testing
A diagnosis may be made before symptoms are present. If a family history is positive for retinoblastoma, frequent eye examinations may be necessary at many stages of the child's development to determine the presence of any tumor. When retinoblastoma is diagnosed, tests will be performed to determine the size, number, location of the tumors, and if the tumors have spread to the other parts of the body. This is called staging and is an important step toward planning a treatment program.
There are various staging systems that can be used for retinoblastoma. Always consult your child's physician for more information on staging. One method of staging is the Reese-Ellsworth stages of retinoblastoma:
- group I - either one or more tumors that are less than 4 disc diameters (DD) in size and located at or behind the equator.*
- group II - either one or more tumors that are 4 to 10 DD in size located at or behind the equator.
- group III - any lesion in front of the equator or any tumor(s) larger than 10 DD.
- group IV - multiple tumors with some or all greater than 10 DD in size or any lesions that extend beyond the back of the eye.
- group V - very large tumors involving more than half of the retina and have spread to other sites in the body.
*The "equator" is an imaginary line that divides the eye into two equal parts.
Specific treatment for retinoblastoma will be determined by your child's physician based on:
- your child's age, health, and medical history
- extent of the disease
- your child's tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
The primary goal of treatment is to remove the tumor and prevent metastasis (spreading) of the cancer to other parts of the body.
Treatment may include one or more of the following:
- enucleation (removal of part or all of the eye or eyes involved with the tumor)
- radiation therapy
- laser therapy or photocoagulation
- thermal therapy
- cryotherapy (uses a freezing process to destroy the tumor)
- fitting and training for a prosthesis
- blind or decreased vision adaptation training
- supportive care (for the side effects of treatment)
- antibiotics (to prevent/treat infection)
Prognosis greatly depends on the following:
- the extent of the disease.
- the size and location of the tumor.
- presence or absence of metastasis.
- the tumor's response to therapy.
- the age and overall health of your child.
- your child's tolerance of specific medications, procedures, or therapies.
- new developments in treatment.
As with any cancer, prognosis and long-term survival can vary greatly from child to child. Every child is unique and treatment and prognosis is structured around the child's needs. Prompt medical attention and aggressive therapy are important for the best prognosis.
Continuous follow-up care is essential for a child diagnosed with retinoblastoma. Secondary cancers have a high incidence among survivors of retinoblastoma. These secondary cancers are not a relapse or recurrent retinoblastoma, but are primary tumors (brand new tumors) of other organs. The most common secondary cancer is osteosarcoma (cancer of the bone). However, retinoblastoma has been linked to melanoma, breast, lung, bladder, and other types of cancers much later in life. The cause of the secondary cancers is not known at this time.
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