Precision Intravitreal Chemotherapy for Localized Vitreous Seeding of Retinoblastoma

Purpose: To describe and evaluate the effectivity of a novel precision intravitreal injection technique for select cases of localized vitreous seeding in retinoblastoma. Methods: Patients with localized vitreous seeds from retinoblastoma received intravitreal chemotherapy via a precision injection technique (P-IVitC) intended to optimize local delivery of melphalan to target seeds. The needle was inserted trans-pars plana and chemotherapy deposited within 3 mm of the target seed(s) under indirect ophthalmoscopic guidance. Without subsequent globe manipulation, the head was then positioned to promote gravity-dependent settling of chemotherapy. Results: There were 8 eyes of 8 patients treated with P-IVitC for active vitreous seeds following adequate solid tumor control with intravenous chemotherapy (n = 3, 38%) or intra-arterial chemotherapy (n = 5, 63%). Viable vitreous seeds were primarily solitary spheres (n = 6, 75%) and measured an average of 2.7 mm in diameter. Vitreous seed resolution (n = 8, 100%) was noted after a mean of 2.6 injections (median 2; range 1-3) of 20 mu g melphalan. There was no recurrence at a mean follow-up of 10.0 months. Only 1 eye had an associated complication (focal retinal pigment epithelial mottling, n = 1, 13%). Conclusions: With direct delivery of chemotherapy to within 3-4 mm of vitreous seed activity, P-IVitC provided complete control of localized vitreous seeds with minimal toxicity.