Feasibility of proton beam therapy as a rescue therapy in heavily pre-treated retinoblastoma eyes

Abstract

<h3>Objectives</h3> Despite the increased risk of subsequent primary tumors (SPT) external beam radiation (EBRT) may be the only therapeutic option to preserve a retinoblastoma eye in which all other available treatment methods have failed to achieve adequate tumor control. Due to their physical properties, proton beam radiation offers the possibility to use the effectiveness of EBRT in tumor treatment and to decisively reduce the otherwise existing treatment-related morbidity in the therapy of hereditary retinoblastoma. <h3>Methods</h3> We report our experiences of proton beam therapy (PBT) as rescue therapy in advanced retinoblastoma disease as final option for eye-preserving therapy, treated from February 2016 to August 2018. <h3>Results</h3> We retrospectively analyzed 15 eyes of 13 children with a mean age of 35 (14-97) months. Mean follow-up was 22 months (range 2-46 months). Minimal follow-up, with the exception of beforehand enucleated eyes, was 12 months. Prior PBT, all eyes were treated with systemic chemotherapy as primary treatment. A mean number of 7.1 (0-16) additional local or systemic treatments due to recurrence or failure of the primary therapy were applied. Indication for PBT was non-feasibility of intraarterial chemotherapy (IAC) in 10 eyes, tumor recurrence or non-response after IAC in another 3 eyes and diffuse infiltrating retinoblastoma with anterior chamber involvement in 2 eyes. 6 eyes (40%) had to be enucleated after a mean time interval of 4.8 (1-8) months. 2 of these 6 eyes showed no viable tumor cells on histopathologic examination. Cataract, as the most common long-term complication, was evident in 44.4% of the preserved eyes. 77.8% of the maintained eyes achieved a best-corrected visual acuity of >20/200. <h3>Conclusion</h3> PBT is a useful treatment modality as a rescue therapy in retinoblastoma eyes with an eye-preserving rate of 60%. In these eyes enucleation was the only treatment alternative. As patients are at lifetime risk of SPTs, however, consistent monitoring and long-term follow-up of these patients is mandatory.