[The efficacy of topotecan versus topotecan combined with melphalan in the treatment of vitreous seeds in retinoblastoma].

Objective: To comparatively evaluate the efficacy and safety of intravitreal topotecan (IVT) versus intravitreal melphalan (IVM) combined with IVT in the treatment of vitreous seeds in retinoblastoma (RB). Methods: Retrospective cohort study. This study collected clinical data from 34 patients with unilateral vitreous seeds in RB who were diagnosed and treated at the Department of Ophthalmology of Eye & ENT Hospital of Fudan University from December 2015 to May 2025. All patients developed refractory or recurrent vitreous seeds after receiving intravenous chemotherapy or intra-arterial chemotherapy. Baseline data, ocular characteristics and detailed treatment histories were analyzed. Patients were treated with IVT (single-drug group) or IVT combined with IVM (double-drug group), which was administered at 4-week intervals until the vitreous seeds disappeared or became stably calcified. The primary outcome measures were the control of vitreous seeds and the globe-salvage rate. The ocular and systemic adverse effects following intravitreal chemotherapy were also recorded. Statistical analyses were performed using the t test, the Mann-Whitney U test and the χ² test. The Kaplan-Meier method was used to plot globe-salvage curves and differences were compared using the log-rank test. Results: There were 21 (61.8%) males and 13 (38.2%) females. The median age at initial diagnosis was 29.5 (19.5, 38.0) months. Among them, 8 (23.5%) had bilateral RB, all with unilateral vitreous seeds and the affected eye received intravitreal chemotherapy and 26 (76.5%) had unilateral RB. Of the affected eyes, 15 (44.1%) were left eyes and 19 (55.9%) were right eyes. According to the International Intraocular Classification of Retinoblastoma, 13 (38.2%) eyes were classified as group E, 20 (58.8%) as group D, and 1 (3.0%) as group C. The single-drug group included 15 eyes (44.1%), with a median age at initial diagnosis of 21.0 (11.0, 30.0) months and a follow-up duration of 19.0±10.0 months. Among them, 1 eye was classified as group C, 7 eyes as group D, and 7 eyes as group E. Each affected eye received a mean of 3.1±1.1 intravitreal injections, with a total topotecan dose of 89.3±34.3 μg per eye. The double-drug group included 19 eyes (55.9%), with a median age at initial diagnosis of 33.0 (22.0, 42.0) months and a follow-up duration of 67.9±30.4 months. Among them, 13 eyes were classified as group D and 6 eyes as group E. Each affected eye received a mean of 5.0±1.7 intravitreal injections, with a total melphalan dose of 111.1±44.5 μg and a total topotecan dose of 74.7±44.0 μg per eye. During the follow-up period, vitreous seeds in all affected eyes in both groups were controlled (100%), and no orbital or systemic metastases were observed. Compared with the double-drug group, the single-drug group exhibited fewer local adverse effects. The incidence of cataract was 0/15 and 9/19, while the incidence of phthisis bulbi was 0/15 and 6/19, respectively (both P<0.05). Some patients in both groups developed retinal pigment epithelial and choroidal atrophy, vascular occlusion or optic nerve atrophy, but the differences were not statistically significant (both P>0.05). The final globe-salvage rates were 14/15 in the single-drug group and 14/19 in the double-drug group. Conclusions: IVT can effectively treat vitreous seeds in RB. Compared with the regimen combining melphalan, the IVT monotherapy is associated with fewer intraocular adverse effects.