Intravitreal Melphalan for Retinoblastoma: The Impact of Toxicity on Recurrence and Ultimate Globe Salvage

Introduction: Intravitreal melphalan (IVM) has emerged as an efficacious treatment for vitreous seeding in retinoblastoma. Although rarely severe, IVM-related toxicity may be treatment limiting. There is paucity of data on the impact of IVM toxicity on new tumor formation and ultimate globe salvage. Objectives: To investigate whether the grade of retinal toxicity post-IVM impacts retinal and seeding tumor recurrence, as well as the overall ability to salvage the eye. Methods: A single-institution retrospective chart review was performed on 47 eyes of 42 patients who received systemic intravenous chemotherapy followed by IVM as salvage treatment for persistent or recurrent vitreous seeding. Chorioretinal toxicity was graded from 0 to 5. Results: Toxicity grade was inversely associated with the risk of recurrence, where a one-unit increase in toxicity grade correlated with nearly a 54% reduction in the odds of tumor recurrence (OR 0.46 [0.25–0.84], p = 0.01). Similarly, toxicity grade was related to enucleation, where a one-unit increase in toxicity grade was associated with a 31% reduction in the odds of undergoing enucleation (OR 0.69 [0.40–1.18], p = 0.17). Conclusions: While retinoblastoma therapy aims to limit toxicity, especially visually significant toxicity, eyes with higher grades of post-IVM toxicity are less likely to have retinal and seeding tumor recurrence.