Purpose: To study the role of external beam radiation therapy (EBRT) for the treatment of retinoblastoma eyes that were not cured by combined systemic chemotherapy and focal consolidation therapy.Methods and Materials: A retrospective case series of 28 eyes for 24 retinoblastoma patients treated by EBRT after the failure of tumor controlled by chemotherapy and focal therapy. The main outcome measures included: international intraocular retinoblastoma classification stage (IIRC) and Reese Ellsworth (RE) stage, tumor seeding, treatment modalities, eye salvage, and survival.Results: The median age at diagnosis was 11 months. There were 14 (58%) males and 20 (83%) bilateral cases. All eyes were treated initially by systemic chemotherapy (range; 6-8 cycles). The dose of radiation used for all eyes was 45 Gray (Gy).The mean follow-up was 75months, and the overall eye salvage rate after EBRT was 13 (46%) eyes: 67% (2/3) for IIRC group B, 71% (5/7) for group C, and 33% (6/18) for group D eyes. Vitreous seeds and tumor stage migration during management by chemotherapy were the most important significant predictive factors for tumor control (p = .001 and 0.033, respectively).Conclusion: Eyes with retinoblastoma that failed chemotherapy followed by focal therapy were controlled with EBRT. However, the presence of vitreous seeds, stage migration during the course of chemotherapy, as well as good vision in the other eye may not justify the known risks of EBRT.
Keywords: Radiation therapy; retinoblastoma; stage migration; vitreous seeds.