Primary Subretinal Seeding in Retinoblastoma: Clinical Presentation and Treatment Outcomes

Introduction: The aim of this study was to describe the clinical features and treatment outcomes of primary subretinal seeding (SRS) in patients with intraocular retinoblastoma (RB). Methods: Descriptive analysis of primary SRS in 47 patients (50 eyes) with RB was performed. Results: Mean age was 19 months (range, 2–72 months), and 55% (n = 26) of the subjects were male. At presentation, the SRS involved two or more quadrants in 88% of eyes. Most seeds appeared yellowish gray (66%) and round to oval in shape (48%). Two-thirds of SRS were seen posterior to the equator and within 5 mm from the main tumor. Associated features included subretinal fluid in 50 eyes (100%), total retinal detachment in 28 eyes (56%), and vitreous seeds in 20 eyes (40%). Treatment included intravenous chemotherapy (IVC) (n = 47; 94%), enucleation (n = 2; 4%), and intra-arterial chemotherapy (n = 1; 2%). SRS treatment included adjunct use of focal transpupillary thermotherapy and/or cryotherapy (n = 20; 40%). Retinal tumor control was achieved in 36 eyes (76%) with 32 eyes (78%) showing a type 3 regression pattern, while SRS completely regressed in 24 (48%) eyes, partially in 15 (30%) and worsened in 2 (4%) eyes. Over a mean follow-up of 30 months (range, 3–68 months), SRS recurrence was noted in 12 eyes (29%), globe salvage was achieved in 39 eyes (78%), and 1 (4%) patient died of presumed metastasis. Conclusion: Primary SRS pose a therapeutic challenge during RB treatment. The SRS responds moderately to systemic IVC, with one-third cases showing SRS recurrence and one-fifth ultimately requiring enucleation.