It can also sometimes help guide treatment choices, since patients with an inherited form of retinoblastoma may be at increased risk for developing recurrent tumors or other types of cancers, particularly when treated with radiation.
People with an inherited form of retinoblastoma who have not undergone radiation treatment have approximately a 26 percent chance of developing cancer in another part of the body within 50 years of the initial diagnosis.
Although most people with the inherited form of retinoblastoma develop bilateral tumors, approximately 15 percent of people with a tumor in only one eye (unilateral) are affected with an inherited form of retinoblastoma.
When a child is diagnosed with retinoblastoma, it is recommended that parents and siblings receive a dilated retinal examination by an ophthalmologist who is experienced in the diagnosis and treatment of the disease.
Patients with trilateral retinoblastoma who receive treatment have an average survival rate of approximately eight months, while those who remain untreated have an average survival rate of approximately one month.
Occasionally, children with retinoblastoma develop trilateral retinoblastoma, which results from the development of an independent brain tumor that forms in a part of the brain called the pineal gland.
If the RB1 gene change/deletion is identified in one of the parents, it can be assumed that the retinoblastoma was inherited and that siblings have a 50 percent chance of inheriting the altered gene.
If the pediatrician suspects retinoblastoma on the basis of these evaluations, he or she will most likely refer the patient to an ophthalmologist (eye doctor) who has experience with retinoblastoma.
People with an inherited form of retinoblastoma are more likely to have a tumor in both eyes (bilateral) and are more likely to have more than one independent tumor (multifocal) in one or both eyes.
Approximately 5 to 8 percent of individuals with retinoblastoma possess a chromosomal abnormality involving the RB1 gene that can be detected by looking at their chromosomes under the microscope.