Solid Tumor: Retinoblastoma
Alternate Names: None
Retinoblastoma is a malignant tumor of the retina, which is a thin membrane on the back of the eye that works like a camera, taking pictures of what you see. The tumors consist of small round cells grouped into structures called rosettes, which are thought to derive from the fotoreceptors of the retina. In many occasions, the tumor is necrotic in the center, with areas of hemorrhage. When the tumors are very large, small portions of them break away from the main mass and remain in suspension in the viscous fluid within the eye called the vitreous. These small tumors are called “vitreous seeds,” and are very difficult to treat. Retinoblastoma also has the potential to spread throughout the retina, into the eye tissue under the retina, into the eye socket, the optic nerve and brain, or more distantly, to the bones and the bone marrow.
Patients may be born with retinoblastoma, but it is rarely diagnosed at birth. Some patients (25-40 percent) are born with a genetic defect that leads to the development of multiple tumors in one or both eyes. The diagnosis of retinoblastoma is usually made before the 3 years of age. The first sign of retinoblastoma is usually a white reflex in the eye, often called a cat’s eye appearance, in which a white-yellow tumor mass is seen through the pupil. Often times, the white reflex is first seen in a photograph of the child’s face. In other children, the first signs of retinoblastoma are complaints of poor vision, or turning of the eye inward or outward. When the tumor is very large, it can cause the pressure of the eye to increase, and the eye becomes very painful.
- An estimated 250-300 children a year will develop retinoblastoma in the United States.
- Retinoblastoma represents about 3 percent of all childhood malignancies.
Children born with bilateral retinoblastoma may pass the retinoblastoma trait to their children (hereditary).
Most of the remaining 60-75 percent have the non-hereditary form of retinoblastoma. However, about 5 percent of these patients may also carry the "retinoblastoma gene" with the risk of passing the trait to their children.
Retinoblastoma serves as the model for understanding the heredity and genetics of childhood cancer.
Clinical Features and Symptoms
Children with a suspicion of having retinoblastoma need to be examined under anesthesia, with the pupils dilated, and have very careful evaluation of the size and number of tumors.
The tumors are also evaluated using MRI and ultrasounds of the eyes.
Since retinoblastoma can also spread outside of the eye, studies of the bones (bone scan), the bone marrow and the spinal fluid are also performed.
- If the tumor is contained within the eye, more than 95 percent of patients can be cured. For those children with tumors in both eyes, close to 70-80 percent of the eyes can be saved, although many of them need radiation therapy.
- Patients with the hereditary form of retinoblastoma have a genetic predisposition to develop other cancers, and continue to develop other cancers outside of the eye throughout their lives.
Treatment depends on whether the tumor affects one eye or both eyes and if the disease has spread to other parts of the body. Different combinations of surgical techniques, radiation therapy or chemotherapy are used as treatment.
Patients with retinoblastoma in only one eye (unilateral) are usually treated with removal of the eye (enucleation). More than 90 percent of these children do not need any more treatment. In the remaining cases, the tumor may have spread to deeper areas within the eye tissues, or into the eye socket, and they receive additional chemotherapy after the surgery. A very small number of children can have tumor invading the brain, or spreading to the bones or the bone marrow. These patients need more intensive chemotherapy, usually including a bone marrow transplant.
In children with multiple or bilateral tumors, the treatment is more conservative, since these children may have both eyes involved and have a tendency to develop new eye tumors until they are 3 years of age. For these reasons, removal of the eye is seldom performed. Instead, patients receive chemotherapy in order to shrink the tumors as much as possible, and the tumors are then treated with what are called “focal treatments.” These include laser therapy, freezing treatments or the use of small radioactive discs. These treatments are applied while the child is under anesthesia. For children with advanced tumors that do not respond to these therapies, it may be required to use radiation therapy or removal of the eye. One of the main goals is to delay radiation and enucleation as long as possible in order to allow for a good growth of the orbit.
In developing countries, children are diagnosed very late, and many children have tumors spreading outside of the eye.
At St. Jude clinical trials are testing new chemotherapy drugs that have better penetration into the eye, in an attempt to avoid radiation therapy or having to surgically remove the eyes. We are also performing biology studies to better understand how retinoblastoma develops. Finally, our research also includes evaluation of how these children develop and how their brains adjust to the visual deficits.
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