Comparison of efficacy and toxicity of intravitreal melphalan formulations for retinoblastoma

OBJECTIVE: Intravitreal melphalan injections are commonly used in the treatment for intraocular retinoblastoma. This study compares retinal toxicity and ocular survival between two formulations, with and without propylene glycol (Alkeran vs. Evomela, respectively). METHODS: A retrospective cohort study of retinoblastoma patients who received intravitreal injections of Alkeran and Evomela at 30 μg from September 2012 to January 2019 at a single tertiary care center were enrolled. Retinal toxicity was measured using electroretinogram (ERG) and compared using a multivariate analysis of 338 injections in 101 eyes of 96 patients. Ocular survival of 163 eyes in 150 patients was compared across formulations using Cox proportional hazards model. Eyes were censored at the time a patient received a dose other than 30 μg. RESULTS: Overall, ERG decline (mean, 95% CI) for each injection was -5.58 μV (-7.17, -3.99). No significant differences in ERG decrement were found between Alkeran (with alcohol) -5.52uV (-6.99, -4.05). and Evomela (without alcohol) -5.65uV (-8.31 to -2.98) formulations (p = 0.93). Ocular survival at 24 months was 93.6% (95% CI 86.2, 97.1) with alcohol and 91.7% (95% CI 53.9, 98.8) without alcohol. The hazard ratio (HR) for without vs with alcohol was 0.50 (95% CI 0.06 to 4.07); no significant difference in ocular survival was found between formulations (p = 0.52) CONCLUSIONS AND RELEVANCE: No differences were found in retinal toxicity and ocular survival between 30 μg intravitreal injections of Alkeran or Evomela for intraocular retinoblastoma. Given the increased stability of Evomela, intravitreal treatment could be expanded to centers without the ability to supply Alkeran due to its shorter safety window; however, Alkeran is less expensive. For those with existing infrastructure, Alkeran is a comparable, cost-effective alternative.