What Is Retinoblastoma?
Retinoblastoma is a malignant (cancerous) tumor of the retina, the thin nerve tissue that lines the back of the eye which senses light and forms images. It may be compared to the film in a camera that perceives images and sends these to the brain for interpretation.
Although retinoblastoma may occur at any age, it most often occurs in younger children before the age of five years. Retinoblastoma affects one in every 18,000 births, with an estimated 250 to 500 cases diagnosed in the United States each year. The tumor may be in one eye only or in both eyes. Retinoblastoma is usually confined to the eye but, if left untreated, is capable of metastasis or spreading to other parts of the body. A similar tumor, called a pinealoma, can occur in the pineal gland at the base of the brain in some patients with a hereditary form of retinoblastoma resulting in a condition called trilateral retinoblastoma.
Stages of Retinoblastoma
To plan treatment for retinoblastoma, your child's doctor needs to know the exact size and location of the tumor(s) to determine the stage of disease. Although there are several staging systems currently available, the most common method is staging by intraocular (inside the eye) and extraocular (extending outside the eye) disease.
- Intraocular retinoblastoma
Cancer is found in one or in both eyes but does not extend beyond the eye into the tissues around the eye or to other parts of the body.
- Extraocular retinoblastoma
The cancer has extended beyond the eye, usually by way of the optic nerve. It may be confined to the tissues around the eye, or it may have spread to other parts of the body.
- Trilateral retinoblastoma
In some patients with bilateral retinoblastoma a related tumor develops in the pineal gland at the base of the brain. The presence of these tumors can result in other neurological symptoms and require neuroimaging of the brain for diagnosis. Trilateral retinoblastoma must be diagnosed promptly when present, as its presence requires different treatment approaches.
- Recurrent retinoblastoma
Recurrent disease means that the cancer has come back or progressed after it has been treated. It may recur in the eye or elsewhere in the body.
- Leukocoria (cat's eye reflex or white pupil). This may be first observed in photographs where the eye appears white rather than reflecting the reddish-orange light from the eye's retina.
- Misaligned eyes (strabismus)
- Blurred vision
Retinoblastoma may be hereditary or nonhereditary. The hereditary form may be in one or both eyes. Most retinoblastoma occurring in only one eye is not hereditary; when the disease occurs in both eyes it is always hereditary. However, while less common, retinoblastoma may occur in only one eye and may still be hereditary and passed on to children, or inherited in siblings. The presence of multiple tumors in the affected single eye raises the chance that the disease may be hereditary. Because of the hereditary factor, brothers and sisters of children with suspected hereditary retinoblastoma should be examined as early as possible to find out if they may have or develop the disease.
If your child has retinoblastoma, particularly the hereditary type, there is an increased chance that he or she may develop a second cancer in later years. These cancers are usually unrelated to the eye, and may affect any organ in the body, but particularly the bone, soft tissue, or skin. Parents should continue taking their child for medical check-ups even after the cancer has been treated.
Tests and Diagnosis
Your child's prognosis (chance of recovery and of retaining sight) and choice of treatment depend on the extent and location of the disease within and outside of the eye. Once retinoblastoma is found, more tests will be done to determine the size of the tumor and whether it has spread to surrounding tissue or to other parts of the body. This is required for the staging discussed above.
Treatment and Drugs
There are many treatment modalities for children with retinoblastoma, and most children can be cured. The type of treatment depends on the extent of the disease within the eye, whether the disease is in one or both eyes, and whether the disease has spread beyond the eye. Treatment options consider both cure of the cancer and preservation of sight or the affected eye, and include the following:
- Enucleation - surgery to remove the eye
- Cryotherapy - the use of extreme cold to destroy cancer cells
- Photocoagulation - the use of laser light to destroy blood vessels that feed the tumor or to heat the tumors so that chemotherapeutic drugs will be more effective.
- Internal or external-beam irradiation therapy - the use of high-energy radiation from x-rays and other sources to destroy cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy) or may be administered by placing radioactive material into or very near the tumor (internal plaque radiation therapy or brachytherapy).
- Chemotherapy - the use of drugs to destroy cancer cells. One form of chemotherapy, called chemoreduction, is used to shrink the size of the tumor(s) so that even if not curative, the smaller tumors will be more amenable to other treatment modalities. Chemotherapy may be administered systemically (by mouth, with injections, or through a vein). In children with retinoblastoma, chemotherapy drugs may also be injected:
- Directly into the fluid that surrounds the brain and spinal cord (intrathecal chemotherapy).
- Directly into the artery that feeds the eye (intra-arterial) for local treatment that has fewer systemic side effects. Intra-arterial chemotherapy would be administered with the help of interventional radiologists, and is used only for tumors that have likely not spread beyond the eye.
Reviewed by Monte A. Del Monte, M.D.