Retinoblastoma is a cancer of the retina, the light-sensing area at the back of the eye.
Retinoblastomas represent about 3% of childhood cancers and almost always occur before age 4. They occur in both eyes at the same time in about 25% of children.
This cancer results from a mutation in certain genes that control eye development. Sometimes the mutation is inherited from a parent or occurs very early during development of the embryo. Children thus affected may pass the mutation on to their offspring, who may also develop retinoblastoma. Other times, the mutation occurs later in embryonic development and only in the embryo's eye cells. This mutation cannot be passed on to offspring. Retinoblastoma is hereditary in all children with cancer in both eyes and in 15 to 20% of children with cancer in one eye.
Retinoblastoma does not usually spread beyond the eye, but it occasionally spreads to the brain along the optic nerve (the nerve that leads from the eye to the brain). It may also spread to other organs, such as the bone marrow.
Symptoms and Diagnosis
Symptoms can include a white pupil or cross-eyes (strabismus). Large retinoblastomas may affect vision but tend to cause few other symptoms.
If a doctor suspects a retinoblastoma, the child is given a general anesthetic, and both eyes are examined. A light and a special lens (indirect ophthalmoscopy) are used to look through the lens and iris at the retina. A general anesthetic is necessary because small children are not able to cooperate during the careful, time-consuming examination required to diagnose retinoblastoma.
The cancer can also be identified by computed tomography (CT) or magnetic resonance imaging (MRI). Both tests help determine whether the cancer has spread to the brain. Doctors may also do a spinal tap (lumbar puncture) to look for cancer cells in a sample of cerebrospinal fluid. Finding cancer cells in this fluid is further evidence that the cancer has spread to the brain.
Because the cancer can spread to the bone marrow, a sample of bone marrow may be removed for examination.
Prognosis and Treatment
Without treatment, most children with retinoblastoma die within 2 years. However, with treatment, children with retinoblastoma are cured more than 90% of the time.
When only one eye is affected and that eye has little or no vision, doctors usually remove the entire eyeball along with part of the optic nerve. When children can see fairly well with the affected eye or when the cancer affects both eyes, doctors sometimes give chemotherapy and try to avoid surgery in an attempt to spare the eyeballs. Chemotherapy drugs include etoposide, carboplatin, vincristine, and cyclophosphamide. The chemotherapy may completely eliminate the cancer. If not, chemotherapy often shrinks the cancer enough that the remainder may be removed with lasers, freezing (cryogenic) probes, or patches containing radioactive material. If these treatments do not eliminate the cancer, doctors may remove the eyeball or give radiation therapy. Sometimes both eyeballs must be removed.
Chemotherapy is also used when the cancer has spread beyond the eye or when the cancer returns after initial treatment.
Radiation therapy to the eye has serious consequences, such as cataracts, decreased vision, chronic dry eye, and wasting of the tissue around the eye. The bones of the face may not grow normally, resulting in a deformed appearance.
After treatment, doctors reexamine the eyes every 2 to 4 months to determine whether the cancer has returned. Children with the hereditary type of retinoblastoma have a particularly high risk of having the cancer recur. Furthermore, within 30 years from the time of diagnosis, as many as 70% of people with a hereditary retinoblastoma develop a second cancer, such as soft-tissue sarcomas, melanomas, and osteosarcomas. Doctors recommend that immediate family members of any child with a retinoblastoma have regular eye examinations. Other young children in the family need to be checked for a retinoblastoma, and adults need to be checked for a retinocytoma, a noncancerous (benign) tumor caused by the same gene. Because family members may have the retinoblastoma gene but not develop the cancer, doctors may suggest that they have DNA analysis to check for the gene.
Last full review/revision January 2009 by David N. Korones, MD