 Retinoblastoma
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Retinoblastoma is a rare cancer of the retina. The retina is the innermost layer of the eye, located at the back of the eye that receives light and images necessary for vision.
About 250 children in the United States are diagnosed with this type of cancer each year. It mostly occurs in children under the age of 5; the highest incidence of the disease occurs between infancy and age 2.
Both males and females are affected equally. Retinoblastoma can occur in either eye; however, in about 25 to 30 percent of the cases, the tumor is present in both eyes. Retinoblastoma cells can, in rare cases, spread (metastasize) to other areas of the body, including the bone marrow.
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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." 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."
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:
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- 70 to 75 percent of retinoblastoma cases involve one eye (unilateral). Of these, 15 to 20 percent are inherited, and the remainder are sporadic.
- 25 percent of retinoblastoma cases are bilateral (both eyes) and hereditary.
- 15 percent of retinoblastoma cases are unilateral (one eye) and hereditary.
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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.
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The following are the most common symptoms of retinoblastoma. However, each child may experience symptoms differently. Symptoms may include:
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- 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
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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.
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In addition to a complete medical and physical examination, diagnostic procedures for retinoblastoma may include:
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- complete eye examination
- funduscopic examination - with the child under anesthesia, the pupils are dilated so the entire retina can be viewed and examined.
- computerized 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
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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.
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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:
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- 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.
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*The "equator" is an imaginary line that divides the eye into two equal parts.
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Specific treatment for retinoblastoma will be determined by your child's physician based on:
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- your child's age, health and medical history
- extent of the disease
- your child's tolerance for specific medications, procedures, or therapies
- how your child's physician expects the disease to progress
- your opinion or preference
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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:
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- surgery
- enucleation (removal of part or all of the eye or eyes involved with the tumor)
- chemotherapy - a drug treatment that works by interfering with the cancer cell's ability to grow or reproduce. Different groups of drugs work in different ways to fight cancer cells and shrink tumors. Chemotherapy may be used alone for some types of cancer or in conjunction with other therapy such as radiation or surgery. Often, a combination of chemotherapy drugs is used to fight a specific cancer. Certain chemotherapy drugs may be given in a specific order depending on the type of cancer it is being used to treat. While chemotherapy can be quite effective in treating certain cancers, the agents do not differentiate normal healthy cells from cancer cells. Because of this, there can be many adverse side effects during treatment. Being able to anticipate these side effects can help the care team, parents, and child prepare, and, in some cases, prevent these symptoms from occurring, if possible.
Chemotherapy is systemic treatment, meaning it is introduced to the bloodstream and travels throughout the body to kill cancer cells. Chemotherapy can be given:
- as an injection into the muscle or fat tissue
- intravenously (directly to the bloodstream; also called IV)
- intrathecally - chemotherapy given directly into the spinal column with a needle
- radiation therapy - using high-energy rays (radiation) from a specialized machine to damage or kill cancer cells and shrink tumors
- stem cell transplant - a treatment involving stem cells, a specific type of cell from which all blood cells develop. Stem cells develop into red blood cells to carry oxygen, white blood cells to fight disease and infection, and platelets to aid in blood clotting. Transplantation of normal stem cells from another person is used to help restore normal blood production in patients whose own ability to make any or all of these blood cells has been compromised by cancer, intensive cancer treatment, or other types of damage or abnormality. The use of cells from another individual is called allogeneic transplantation. Stem cells collected form patients themselves prior to intensive treatment can also be used to supplement the recovery of the patient's own cells after particularly aggressive course of chemotherapy or radiation therapy. The use of a patient's own cells is referred to as autologous transplantation.
Stem cell transplantation and the treatment needed to manage its effects are complex. Your physician will give you more detailed information on what to expect.
- laser therapy or photocoagulation
- cryotherapy - uses a freezing process to destroy the tumor
- fitting and training for a prosthesis
- blind or decreased vision adaptation training
- supportive care - any type of treatment to prevent and treat infections, side effects of treatments, and complications, and to keep your child comfortable during treatment
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Prognosis greatly depends on the following:
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- 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.
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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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Children's Hospital and Dana-Farber Cancer Institute are conducting numerous research studies that will help clinicians better understand and treat retinoblastoma.
In addition, the Dana-Farber/Children's Transplant Program is one of only eight institutions around the country that are investigating the use of umbilical cord transplantation. Also under study is a novel method for preventing graft versus host disease, a serious complication that occurs when transplanted cells do not recognize the tissues and organs of the recipient's body and react against the recipient's tissue. The result of this treatment approach, if it continues to be as successful, will be that the degree of match between donor and the recipient will not need to be particularly close, greatly increasing the pool of potential donors for each patient. This could also eliminate the need for long-term drug therapy traditionally needed to treat graft versus host disease.
Other types of treatment currently being studied include:
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- angiogenesis inhibitors - substances that may be able to prevent the growth of tumors by blocking the formation of new blood vessels that feed the tumors
- biological therapies - a wide range of substances that may be able to involve the body's own immune system to fight cancer or lessen harmful side effects of some treatments
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