The Evolution of Radiation Therapy for Retinoblastoma: The MD Anderson Cancer Center Experience.

Purpose: The role of radiation therapy (RT) for retinoblastoma (Rb) has significantly evolved from first-line to salvage therapy. The objectives of our study were to evaluate efficacy of proton RT (PRT) and other advanced RT techniques for Rb and to observe evolving trends in RT use.

Materials And Methods: An analysis of patients with Rb who received RT between 1990 and 2012 was conducted. Thirty-nine patients with 70 affected eyes were identified. Of these, 47 eyes were treated with RT with photon or electron RT (ERT), PRT, or brachytherapy (BRT). The clinical history, treatment details, and tumor outcomes were reviewed for all patients.

Results: Radiation therapy was first-line treatment in 14 eyes, second-line in 4, postoperative in 4, and salvage in 25. Median length of follow-up was 8 years for all patients, and 10, 3, and 5 years for ERT, PRT, and BRT, respectively. Overall survival was 97.4%. In total, 16 (34.0%) eyes required enucleation after RT. Median PRT dose was 36 Gy (RBE) (range, 36-45 Gy [RBE]), ERT dose was 45 Gy (range, 36-46 Gy), and BRT dose was 45 Gy (range, 36-45 Gy). A higher proportion of PRT patients (93.8%) than ERT patients (51.9%) were treated in the salvage setting ( < .01). Among patients with International Classification for Intraocular Retinoblastoma stage D and E disease, 6 of 11 (54.5%) ERT patients required enucleation and 5 of 13 (38.5%) PRT patients required enucleation.

Conclusion: This study represents a large series of patients treated with PRT, ERT, and BRT for Rb and reports favorable efficacy and toxicity. Patients treated with salvage PRT are typically heavily pretreated and have advanced disease. Despite more advanced disease, patients treated with PRT with lower RT doses achieve comparable salvage and enucleation-free rates to ERT. Chemoreduction followed by focal treatments should be standard of care when clinically feasible, with PRT considered in the salvage setting.