Combination of Brachytherapy and Intravitreal Chemotherapy in the Treatment of Retinoblastoma with Vitreous Seeding

Purpose: The aim of this study was to report the efficacy of combined intravitreal chemotherapy (IVC) and ruthenium-106 brachytherapy in retinoblastoma, either as first-line or second-line treatment, following systemic chemoreduction or intra-arterial chemotherapy. Methods: Retrospective data of 18 eyes from 18 patients treated with IVC and brachytherapy from August 2014 to December 2019 were collected. Results: The method described was our first-line therapy in 6 patients, whereas it was used as second-line treatment after chemoreduction in the remaining 12 patients. The eyes showed the following classification at initial presentation: 2 group B eyes, 3 group C eyes, and 13 group D eyes. The mean follow-up was 19.5 months (range 2-53 months). The mean patient age at brachytherapy was 34.0 months (range 15-83 months). The median prescribed dose at the tumour base and apex was 574.5 +/- 306.7 Gy and 88.5 +/- 12.2 Gy, respectively. The ocular retention rate was 66.7%. Six eyes had to be enucleated due to uncontrollable subretinal and recurrent vitreous seeding, tumour relapse, recurrence of a solid tumour elsewhere in the eye, and persistent vitreous bleeding with loss of tumour control. The mean number of intravitreal injections of melphalan was 5.0. Two patients received a simultaneous injection of topotecan for insufficient therapeutic response. With regard to radiogenic complications, we could observe temporary retinal and vitreous bleeding (27.8%), serous retinal detachment (44.4%), and radiogenic maculopathy and retinopathy (11.1%). None of the children showed metastatic disease during follow-up. Conclusion: Ruthenium-106 plaque therapy in combination with IVC is an effective local therapy with good tumour control rates even in advanced eyes. Overall, the analysed therapeutic approach shows an acceptable side-effect profile, especially when considering that external-beam radiation therapy and systemic polychemotherapy or at least the number of cycles needed, with their increased incidence of adverse events, can thus be avoided.