Radiation Therapy

EBRT. EBRT doses ranging from 35 Gy to 46 Gy usually result in long-term remissions. Because of the need to sedate young children and the intricacies of field planning, special expertise in pediatric radiation therapy is important. Radiation therapy is used in cases of progression after conservative approaches, in patients with extraocular extension, and as part of the management of patients with metastatic disease.Newer methods of delivering EBRT are being applied to reduce adverse long-term effects. This includes intensity-modulated radiation therapy and proton-beam radiation therapy (charged-particle radiation therapy).[56-59] Preliminary data suggest that proton radiation therapy is associated with a lower risk of radiation-induced malignancy in survivors of heritable retinoblastoma. In a nonrandomized study that compared two contemporary cohorts of patients with heritable retinoblastoma who were treated with either photon or proton radiation therapy, the 10-year cumulative incidence of radiation-induced SNs was significantly different between the two groups (0% for proton radiation vs. 14% for photon radiation, P = .015).[60]EBRT in infants causes growth failure of the orbital bones and results in cosmetic deformity. EBRT also increases the risk of SNs in children with heritable retinoblastoma.

Brachytherapy (plaque radiation therapy). Indications for plaque radiation therapy include solitary tumors with a diameter ranging between 6 mm and 15 mm, tumor thickness of 10 mm or less, and tumor location of more than 3 mm from the optic disc or fovea. The most commonly used radioisotope is iodine I 125, although others such as iridium Ir 192 and ruthenium Ru 106 are also effective. In combination with the appropriate use of chemotherapy and other forms of focal consolidation, brachytherapy can be very effective in the treatment of localized retinal tumors that are not amenable to other means of local therapy.[61-63]