Not All Seeds Are Created Equal: Seed Classification Is Predictive of Outcomes in Retinoblastoma.

OBJECTIVE: Intravitreal chemotherapy has emerged as an important modality for treating vitreous seeding in retinoblastoma. A classification system has been described as predictive of response to intravitreal melphalan (IVM) in patients treated predominantly with primary intra-arterial chemotherapy. The objective of this study is to evaluate the outcomes of retinoblastoma treated with intravenous chemotherapy and IVM as salvage for vitreous seeding, and further to determine whether vitreous seed classification (dust, spheres, cloud) is predictive of the total number and dose of IVM injections required for treatment in this cohort.

DESIGN: A nonrandomized retrospective review.

PARTICIPANTS: Retinoblastoma patients treated at a single center with intravenous chemotherapy and IVM.

METHODS: Retrospective review of patients with vitreous seeding from retinoblastoma treated with intravenous chemotherapy and IVM from 2012 to 2016.

MAIN OUTCOME MEASURES: Primary outcome measure was eradication of seeds and globe salvage. Secondary measures included IVM-associated toxicity and complications.

RESULTS: Overall, 28 eyes of 25 patients were included, with a total of 110 IVM injections. By seed classification, eyes with dust (n = 15) required a median of 3 injections, spheres (n = 8) required 4 injections, and clouds (n = 5) required 6 injections. Spherical seeds were only seen in recurrent vitreous seeding. Of the 28 treated eyes, 9 were enucleated, 6 for recurrent retinal disease, resulting in an overall globe salvage rate of 68%. The salvage rate secondary to active retinoblastoma was 79%. Dust classification was the most prevalent seeding type of the 9 enucleated eyes. There was 100% regression of vitreous seeds after intravitreal injection and no eye was treated with radiation or enucleated for seeding. Twelve eyes demonstrated grade 3 or greater IVM-associated retinal or anterior segment toxicity post injection. Mean follow-up was 33 months (range, 9-51 months).

CONCLUSIONS: IVM is an effective treatment for vitreous seeding after intravenous chemotherapy for retinoblastoma. As with eyes treated with intra-arterial chemotherapy, seed classification is predictive of the total number and dose of IVM injections in eyes treated with intravenous chemotherapy. Eyes with clouds required significantly more injections than eyes with dust or spheres.