Radiation induced optic neuropathy: Does treatment modality influence the risk?

Radiation induced optic neuropathy (RION) is a rare but disastrous complication of radiation therapy in treatment of periorbital tumors. The objective of this study is to investigate the incidence of RION in series of patients treated from peri orbital tumors by recent photon and proton irradiation modalities. We searched the Pub Med database for studies in periorbital tumors including base of skull, sinonasal, pituitary, nasopharyngeal tumors and craniopharyngioma treated with Intensity modulated radiotherapy (IMRT) and with proton beam therapy (PBT) between 1992 and 2017 excluding metastatic tumors, lymphomas, pediatric series, those treated mainly with chemotherapy, target therapy and those written in languages other than English and French. The result retrieved 421 articles that were revised by the panel. Fourteen articles with IMRT and 27 with PBT reported usable data for the review from which 31studies that had pointed to the doses to the optic nerve (ON) and/or optic chiasm (OC) and incidence of RION have been analyzed. We have found that the incidence of RION had been reported fairly in both modalities and many other factors related to the patient, tumor, and irradiation process interplay in its development. We have concluded that proper treatment planning, good selection of treatment modality, adherence to dose constraints applied to critical structures all along with regular oncological and ophthalmological follow up, control of co-morbidities and early intervention, could help reducing its magnitude.