External beam radiation for retinoblastoma.

R etinoblastoma, a malignant retinal tumor of childhood, involves both eyes in one third of cases. Untreated, it is universally fatal, but with present techniques the survival rate is 90%.1 The goals of treatment are preservation of both life and sight. Among the modalities presently used to treat the tumor, radiation therapy is most commonly employed, but such other techniques as diathermy, light coagulation, cryopexy, chemotherapy, surgical enucleation, and exenteration are important resources for an ophthalmic onocolgist.2 The first case of retinoblastoma was described in 1765 by a London surgeon.3 In 1864 Virchow identified the tumor and called it a "glioma of the retina". Perhaps it was because the tumor was thought to be of glial origin (and it is known that glial tumors responded poorly to radiation) that it was not until 75 years ago that the first retinoblastoma was successfully treated with radiation.4 In fact, it was not until 1926 that the term retinoblastoma was universally adopted. Since then it has been repeatedly emphasized that this tumor originates from the nuclear layers of the retina and not from glial cells. As the indications, contraindications, and complexities of radiation have been learned through trial and error, the usefulness of radiation therapy for retinoblastoma has become better established.