Iodine-125 Plaque Radiotherapy for Retinoblastoma Recurrence Following Intra-arterial Chemotherapy.

Abstract

To assess the efficacy and toxicity of Iodine-125 (I-125) plaque radiotherapy for retinoblastoma following intra-arterial chemotherapy (IAC). Clinical records of patients with retinoblastoma who received I-125 plaque radiotherapy after IAC at the Ocular Oncology Service at Wills Eye Hospital between December 1, 2009 and April 30, 2020, were retrospectively reviewed. Forty-one retinoblastomas in 41 eyes of 41 patients were treated with I-125 plaque radiotherapy after IAC at a median age of 32 months. The indication for plaque radiotherapy was solid tumor recurrence with or without overlying subretinal/vitreous seeds (n = 33, 80%), subretinal seeds alone (n = 6, 15%), and vitreous seeds alone (n = 2, 5%). The median irradiated basal diameter and thickness was 9 and 4 mm, respectively. Mean radiation dose to tumor apex was 3,483 centigray (cGy) delivered at mean rate of 35 cGy/hr. The irradiated site was controlled in 39 eyes (95%) at a median of 20 months after plaque radiotherapy for solid tumor (31 of 33, 94%), subretinal (6 of 6,100%), and vitreous seeds (2 of 2, 100%). A subgroup of tumors occurring within an ischemic retinal/choroidal field was identified on fluorescein angiography (n = 24) and demonstrated control in 22 of 24 (92%). Using Kaplan-Meier analysis, radiation complications at 2 years included vitreous hemorrhage (37%), retinopathy (28%), papillopathy (18%), and cataract (18%). Five eyes (12%) were enucleated for recurrence outside the irradiated area, chronic vitreous hemorrhage, and/or total retinal detachment. Iodine-125 plaque radiotherapy provided 95% control for retinoblastoma tumors that failed IAC, including those in ischemic fields untreatable with further chemotherapy. Radiation complications should be anticipated in eyes exposed to substantial chemotherapy. [J Pediatr Ophthalmol Strabismus. 2022;59(3):164-171.].