Evaluation of Tolerance to Robotic Radiosurgery–Based Stereotactic Radiation Therapy of Primary Intraocular Uveal Melanoma

Abstract

This study was undertaken to assess the effect and evaluate tolerance on CyberKnife-based stereotactic radiotherapy treatment (CK-based SRT) by rate of complications in patient’s group suffering from primary intraocular uveal melanoma. Doses for patients with intraocular tumor undergoing CK-based SRT are often challenging due to the close proximity of optic apparatuses. We evaluate clinical outcomes and the dose plans of 20 patients treated by 3 do 14 with median 5 fractions. The PTV volume ranged from 1.20 - 202.90 cm3 (median 4.76 cm3, mean 21.76 cm3 ± SD 51.44). The prescription dose was 20-50 Gy with median value 50 Gy prescribed to the 80% isodose. The eye’s fixation system with the polymetric device was used to fix the eye position. The device was attached to the mask system in cranio-caudal orientation and placed in front of the diseased eye. The patient was looking at the black point placed at the arm of the eye’s fixation system. CK-based SRT of intraocular tumors were evaluated by: rate of complication, PTV coverage and conformity index (CI), the maximum dose to the optic nerve, lens, chiasma and lacrimal gland. Rate of complications is strongly correlated with tumor location to avoid theme it’s require keeping dose within tolerance limits in such OAR's: lacrimal gland and cornea, lens, optic nerve, extraocular muscles, retina (or posterior eyewall at all), posterior chamber. Median follow-up was 25 months (range 11–25). The treatment was well tolerated by all patients and the stable position of the eye was obtained. Due to tumor proximity to OARs, at least one structure must be sacrificed to achieve proper tumor coverage. Within minimum 11-month follow-up period no grade-4 sequelae (requiring enucleation) was discovered. Table 1 showed rate of complications. Average treatment parameters were: PTV coverage 79.77 – 99.17 % (median 95.67 %, mean 94.51 % ± SD 5.07), CI 1.05 – 1.38 (median 1.13, mean 1.14 ± SD 0.08). The maximum dose to OARs were for: the optic nerve 9.87 – 55.36 Gy (median 29,87 Gy, mean 31.30 Gy ± SD 13.71), lens 2.10 – 35.49 Gy (median 7.48 Gy, mean 10.23 Gy ± SD 8.61), chiasma 0.87 – 30.65 Gy (median 6.96 Gy, mean 8.69 Gy ± SD 7.50) and lacrimal gland 6.50 – 51.34 Gy (median 16.31 Gy, mean 22.11 Gy ± SD 14.72). The results of this study demonstrated good clinical outcome for CK-based SRT of intraocular tumors. More than one year follow up reported that the salvage therapy was unneeded in all cases. CK-based SRT appeared to be a relatively safe technique in treating intraocular tumors within or near optic apparatuses. CK-based SRT provides excellent tumor coverage without delivering excessive dose to OARs and provided that the dose to the optic apparatuses were limited.Abstract 2884Intraocular complicationsGrade-1Grade-2Grade-3Kearatoconjuctivistis521Cataract formation133Radiation-induced retinopathy1053Choroidal vasculopathy1161Optic neuropathy332Scleral necrosis110Extraocular muscle deteriorations100Neovascular glaucoma331 Open table in a new tab