...continued

Every time the unilateral retinoblastoma parent has another child, the chance of that child developing retinoblastoma is 7% to 15%. On the other hand, 85% to 93% of the offspring of a unilateral retinoblastoma parent will not develop the disease.

If neither parent had retinoblastoma:
The situation where neither parent has had retinoblastoma is the most common and the most difficult to explain. Approximately one out of every 100 patients who has retinoblastoma appears to somehow destroy the tumor without treatment, or perhaps has a form of the disease which is not capable of spreading. This is why both parents are encouraged to have a dilated retinal exam. One percent of the time, there is evidence of a cured or limited form of retinoblastoma in the eye of a parent who was never aware of having had retinoblastoma and was never treated for it. In that case, 45% of that parent's children will develop retinoblastoma.

More confusing, and rarer, is the possibility that a parent has the gene for retinoblastoma and can pass it on to his or her children without having any evidence of retinoblastoma in the eye. This is called the carrier state and it means that the parent carries the gene but not the disease. In this case, 45% of their children will be affected. Each of the examples listed here explains how a parent who never had retinoblastoma can have many children affected with bilateral retinoblastoma.

The most common situation is where neither parent has the gene for retinoblastoma but has a child born with retinoblastoma. If the parents are genetically normal, the chance of another child having retinoblastoma is 1 in 15,000 to 1 in 20,000.



David H. Abramson, M.D., F.A.C.S.

“David H. Abramson, MD, FACS
Chief, Ophthalmic Oncology Service
Memorial Sloan-Kettering Cancer Center

Professor of Ophthalmology,
New York Presbyterian Hospital-Weill Cornell Medical College