What are the risk factors for retinoblastoma?
A risk factor is anything that affects a person’s chance of getting a disease such as cancer. But risk factors don’t tell us everything. Different cancers have different risk factors.
Lifestyle-related risk factors such as body weight, physical activity, diet, and tobacco use play a major role in many adult cancers. But these factors usually take many years to influence cancer risk, and they are not thought to play much of a role in childhood cancers, including retinoblastomas.
Most children diagnosed with retinoblastoma are younger than 3 years old. Most congenital or hereditary retinoblastomas are found during the first year of life, while non-inherited retinoblastomas tend to be diagnosed in 1- and 2-year-olds. Retinoblastomas are rare in older children and in adults.
About 1 out of 3 cases of retinoblastoma are caused by a mutation (change) in the RB1 gene that is present in all the cells of the child’s body. But of these cases, only about 1 in 4 is inherited from one of the child’s parents. In the rest, the gene mutation has not been inherited, but has occurred during early development in the womb. Children born with a mutation in the RB1 gene usually develop retinoblastoma in both eyes. Regardless of whether the mutated RB1 gene was inherited from a parent or not, because these children have the mutated gene in all of their cells, they have a 1 in 2 chance of eventually passing it on to their children.
The remaining 2 out of 3 cases occur as a result of a random RB1 gene mutation that occurs only in one cell of one eye. These cancers are not inherited from a parent, and children who have them do not pass on a greatly increased risk of retinoblastoma to their children. Non-hereditary retinoblastomas always affect one eye only.
The way in which inherited gene changes make certain children likely to develop retinoblastoma is explained in the next section, “Do we know what causes retinoblastoma?”
Last Medical Review: 08/06/2012
Last Revised: 08/06/2012