Applications of iodine-125 plaque radiotherapy for residual or recurrent retinoblastoma

Objective: To determine the role of iodine-125 plaque radiotherapy (IPR) as a secondary treatment for localized (solitary or multiple) residual (partially regressed) or recurrent (regrowth after ≥6 months stability) retinoblastoma in the era of systemic and/or regional chemotherapy. Design: A single-institute retrospective, noncomparative, interventional case series managed between July 2014 and June 2019. Participants: Thirteen consecutive eyes of 12 patients with 14 residual or recurrent retinoblastoma tumors treated with IPR. Patients who had to follow up <1 year post-IPR were excluded except for those who had enucleation. Methods: Data collected included pre-IPR treatments, tumor characteristics at IPR, and post-IPR anatomical outcome (local tumor control and globe salvage) and functional outcome (radiation complications). Results: Local tumor control was achievable in 12 of 14 tumors. Local recurrences were observed in 2 of 5 tumors that exhibited fish-flesh regression after IPR (p = 0.04). Globe salvage was possible in 11 eyes (12 tumors). Only 2 eyes were legally blind and the remaining 9 eyes had vision >20/125. Radiation-induced complications included radiation retinopathy (4/11), radiation papillopathy (1/11), diffuse vitreous hemorrhage (4/11). Eyes with fish-flesh-regressed tumours tended to show more complications, but were statistically insignificant (p = 0.09, Fisher exact test). There was no association of time to IPR (early <6 months vs late >6 months) with occurrence of tumor recurrence or complications (p > 0.05). Conclusion: IPR offers satisfactory local tumor control and globe salvage in localized recurrent/residual retinoblastoma. Fish-flesh tumor regression after IPR should be closely monitored for further recurrences. (author)