Comparing Incidence of Cataract Formation in Lens-Sparing Versus Whole-Eye Irradiation in Patients with Retinoblastoma

Abstract

Retinoblastoma is the most common intraocular tumor in children with an incidence of about 300 cases per year. Thanks to treatment advances, the prognosis for retinoblastoma patients is excellent with a five-year overall survival rate of 95%. However, previous work has suggested that radiotherapy for patients with retinoblastoma results in a high risk of developing cataracts. Based on each patient’s individual stage at presentation, treatment plans were developed to either irradiate the whole eye or a smaller volume that excluded the lens. In this study, we investigated whether lens-sparing IMRT treatment plans resulted in a significantly lower incidence of post-radiation cataracts when compared to the whole-eye radiation treatment plans. We conducted a retrospective analysis of 66 patients (74 eyes) treated for retinoblastoma with IMRT at our institution from 1999-2015. Of these 66 patients, 7 patients were lost to follow-up, 1 patient died before meeting the 1-year minimum requirement of follow-up, and 2 patients received orbit radiation after bilateral enucleation. A total of 56 patients (35 males, 21 females) were included in our results. Two eyes were excluded for having cataracts prior to treatment and one orbit was excluded for receiving radiation after enucleation. Of the remaining 71 eyes, 57 eyes received whole-eye irradiation and 14 were treated with lens-sparing IMRT. Treatment groups did not differ significantly by age or sex but the whole-eye group had higher stage disease (p < .001). All patients were examined by ophthalmologists at our institution. We recorded the incidence of cataracts and enucleation post radiotherapy. Cataract incidence was reported as “cataract-free eye survival” and the percentage of eyes not enucleated was reported as “globe salvage rate”. Cataract-free eye survival was estimated as Kaplan-Meier survival curves. Five-year cataract-free eye survival was significantly higher (p < .001) for eyes treated with a lens-sparing approach (64.5%) than those treated with whole-eye irradiation (11.6%). There was no significant difference in 5-year globe salvage rates, which were 45/57 (78.9%) for whole-eye and 13/14 (92.9%) for lens-sparing patients. There was a significant difference (p = 0.005) in mean lens dose received by eyes that developed cataracts (33.8 Gy) versus eyes that remained cataract-free (21.7 Gy). Median follow-up time was 4 years for eyes that remained cataract-free. Patients treated with a lens-sparing technique were less likely to develop cataracts than patients treated with whole-eye irradiation. We did not find any difference in globe salvage rates between the two techniques. These findings suggest that a lens-sparing approach may reduce late effects compared to whole-eye irradiation for treatment of carefully selected cases of retinoblastoma. Whole-eye irradiation is recommended for advanced stages of disease complicated by retinal detachment or extensive vitreous seeding.