Diseases & Conditions
Retinoblastoma is a cancer of the retina, the light-sensing area at the back of the eye.
Retinoblastomas represent about 2% of childhood cancers and almost always occur before age 4. They occur in both eyes at the same time in 20 to 30% of children. This cancer is the result of damage to specific, known genes that control eye development. Sometimes a damaged gene is inherited from a parent or becomes damaged very early during embryonic development. Children with this type of damage may pass the defective gene on to their offspring, who may also develop retinoblastoma. Other times, genes are damaged later in embryonic development only in the embryo's eye cells. This damage cannot be passed on to offspring. Retinoblastoma is hereditary in all of the children with cancer in both eyes and in 15 to 20% of children with cancer in one eye.
Retinoblastoma usually spreads to the brain along the optic nerve (the nerve that leads from the eye to the brain). However, it also may spread to other organs, such as the bone marrow.
Symptoms and Diagnosis
Symptoms of a retinoblastoma can include a white pupil or strabismus (cross-eyes). Retinoblastomas of sufficient size also may affect vision but tend to produce few other symptoms.
If a doctor suspects a retinoblastoma, the child is given general anesthesia and both eyes are examined by looking at the retina through the lens and iris; general anesthesia 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 also look for cancer cells in a sample of cerebrospinal fluid (taken by spinal tap [lumbar puncture]); finding cancer cells 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 is obtained 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 there is significant vision in the affected eye, or 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 Some Trade Names PARAPLATIN , vincristine Some Trade Names ONCOVIN , and cyclophosphamide Some Trade Names CYTOXAN . The chemotherapy may completely eliminate the cancer and often shrinks it 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 if the cancer returns after initial treatment.
Radiation therapy to the eye has significant consequences, such as cataracts, decreased vision, chronic dry eye, and wasting of the tissue around the eye. The bones of the face may fail to grow normally, resulting in a deformed appearance.
After treatment, doctors re-examine 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 50 years from the time of diagnosis, as many as 50% of those 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 examined for a retinoblastoma, and adults need to be examined for a retinocytoma, a noncancerous tumor caused by the same gene. Family members who have no evidence of cancer can have their DNA analyzed to see if they carry the retinoblastoma gene.
Last full review/revision February 2003
Source: The Merck Manual Home Edition