Effect Of Robotic Stereotactic Radiotherapy For Parasellar Tumors On The Eye Structure And Function

Abstract

To evaluate radiation-induced effect on the anterior and posterior segment of the eye in patients undergoing robotic stereotactic radiotherapy for parasellar tumors A prospective analysis was performed on 34 patients (68 eyes) undergoing CK radiotherapy for parasellar tumors from 2010 to 2015. A total of 10 patients were diagnosed with cavernous sinus meningioma, 9 with pituitary adenoma, 5 with meningioma in the region close to optic chiasm, 5 with meningioma of the anterior and middle cranial fossa, 3 with craniopharyngioma, and 2 with meningioma of the orbit. All treatment plans were designed to fulfill Timmermann criteria for the optic pathway. Doses delivered to eye structures were in the range of 1-2227 cGy. Radiation-induced impact on the eye was evaluated based on the changes in the condition of the eye surface, central corneal thickness (CCT), endothelial cell density (ECD), lens densitometry, central macular thickness (CMT), retinal nerve fiber layer (RNFL) in the proximal eye (on the side of the tumor) and in the distal eye (on the opposite side). Best-corrected visual acuity (BCVA), intraocular pressure (IOP), and visual evoked potentials (VEP) were analyzed as functional features. All ophthalmological examinations were performed before radiotherapy and at 6, 12, 18 and 24 months after radiotherapy. There were no statistically significant changes in the BCVA, IOP, condition of the eye surface, CCT, lens densitometry and CMT during the 24-month follow-up period. We observed significant decrease of ECD for all observation intervals when compared to EDC before radiotherapy. The decrease in ECD was greater than approximated age-related physiological loss (0.3% vs 1.9% ±0.5% per year). However, no significant correlation was found between the radiation dose delivered to the cornea and the change in ECD. We observed statistically significant decrease of RNFL in all observation time points. In 6 eyes in (5 patients) the decrease of RNFL was greater than 10%. There was also no correlation between dose delivered to optic pathway and decrease of RNFL. Moreover, doses delivered to individual parts of the optic pathway did not differ significantly for the eyes with 10% drop of RNFL more compared to doses delivered for other eyes. Changes of RNFL were not significant enough to affect visual function. We did not observe significant changes for VEP latency but a significant decrease in VEP amplitude was observed. Robotic RT is a precise and advanced treatment modality with a high safety profile and a low risk for radiation-induced complications in the anterior and posterior segment of the eye. Detailed ophthalmological examination showed significant changes in corneal structure (decrease of ECD) and optic nerve structure (decrease of RNFL) after radiotherapy. Structural changes did not result in alteration of visual function.