External beam radiation in the treatment of retino-blastoma

Purpose. To review the outcome of external beam radiation therapy (EBRT) for retinoblastoma with regard to tumor control, vision, and complications. Methods. Medical records of 26 children (33 eyes) treated from 1975-1994 were reviewed. Six cases were unilateral and 20 bilateral. Fourteen treated eyes were classified as Reese-Ellsworth Group I-III and 13 as Group IV-V. Five orbits were treated prophylactically after primary enucleation with optic nerve involvement, and one was treated for tumor recurrence after enucleation. Twenty-three eyes/orbits were treated via anterior port only, 8 via lateral port only, and 2 via combined anterior and lateral ports. Median dose was 4552 cGy (range 3620-5040 cGy). Ten eyes were treated with a hyperfractionation scheme using b.i.d. 100 cGy doses; the other 23 eyes received 3-5 fractions of 180-400 cGy per week. Seven children received chemotherapy in conjunction with EBRT. Results. Twenty-five of 26 children remain alive with no evidence of disease 14-247 months (median 112) after treatment. Twenty-three of 27 eyes were preserved with useful vision. Cataract developed in 15 of 17 eyes that received anterior port treatment and 1 of 6 that received only lateral port treatment. One child, who had sickle trait, developed severe retinopathy, and one developed significant keratopathy. Four eyes required enucleation for residual or recurrent active disease. Two children developed second malignancies within the irradiated field; one died from malignant fibrous histiocytoma. Conclusions. EBRT provides excellent long-term disease control and a high rate of vision preservation in children with retinoblastoma. Except for cataract, significant complications are infrequent during the childhood years following treatment.