Retinoblastoma, a malignancy of the retina of the eye, is very rare, but is the most common eye tumor in children, usually occurring before the age of five. The disease accounts for 3% of cancers in children.
About 40% of retinoblastoma cases are hereditary. In inherited retinoblastoma, one mutation in a tumor suppressor gene located on chromosome #13 is inherited from a parent, and a second mutation occurs during the development of the retina. In sporadic retinoblastoma, both mutations occur by chance during retinal development.
Unilateral retinoblastoma affects one eye and accounts for about 75% of cases. It can either be hereditary or sporadic. The latter usually occurs in children over age one and is about 75% to 80% of unilateral cases.
Bilateral retinoblastoma affects both eyes, and usually indicates a genetic influence. In one-fourth of cases, there is a positive family history. A new mutation occurs in about 75% of cases. The disease can slso be the result of inheritance from a parent who carries but does not have symptoms of retinoblastoma. About 10% of carriers do not develop the disease. Patients with bilateral retinoblastoma are usually diagnosed at a younger age (under one year old) than those with unilateral disease.
In trilateral retinoblastoma, children with inherited retinoblastoma develop an associated intracranial neuroblastic (originating in primitive nerve cells) tumor. These tumors are rare, occurring in about 5% of patients with bilateral retinoblastoma.
Several procedures are used to diagnose retinoblastoma, including a complete funduscopic eye exam, in which the eye is anesthetized, and the pupils dilated so the retina can be examined. Other procedures that may be done are CT scan, magnetic resonance imaging (MRI), blood tests and DNA and/or genetic testing.
If there is family history of retinoblastoma, frequent examinations are performed at many stages throughout the child’s development to see if any tumors have formed. Diagnosis may be made before there are any symptoms.
After a diagnosis is made, staging, or testing to determine size, number, location and whether or not the tumors have spread to other parts of the body, will be performed, and is an important part of designing a treatment plan.
The main goal of treatment for retinoblastoma at MD Anderson is to treat the tumor and prevent the spread of the cancer to other parts of the body. The eye is spared whenever possible, but may require removal.
Laser treatment, or photocoagulation, is a very successful treatment for small tumors that are confined to the retina but do not involve the optic disc or the area near it called the macula.
Cryotherapy, or freezing treatment, is performed in multiple sessions to treat small, peripheral tumors.
Chemotherapy may be used to reduce the size of the tumor to maximize the effect of localized therapy such as laser or cryotherapy. It may also allow a lower dose of radiation to be used.
Radiation therapy is a very effective treatment for retinoblastoma. Two types of radiation therapy may be used, depending upon the size and location of the tumor and the extent of disease: Plaque radiotherapy (also known as brachytherapy) or external beam radiotherapy.
Enucleation surgery, or removal of the eye, may be performed when the tumor fills more than half the eye, when other structures in the eye are involved or when the retina is detached. Because tumors are detected earlier now than in the past, and more conservative treatments can be used, there has been a significant decrease in enucleation.