ESTRO 2022 - Abstract Book

S911

Abstract book

ESTRO 2022

response was seen in 13 patients, seven of them had more than one tumor lesion at baseline. Two of these seven patients did not receive RT; four of them had a RT of all lesions; so that we could observe a possible abscopal remission effect in only one case. 21 (25.3%) severe (grade 3-4) immune-mediated adverse events were registered. The toxicity profile was similar to previous pivotal studies, with the exception of grade 1 endocrine toxicity, which occurred in 42.2% of patients in our cohort. We did not observe any severe radiation toxicity. Conclusion The combination of PD-1-inhibitor therapy and RT is feasible according to our study. Despite the absence of the abscopal effect, RT might have a positive effect on survival rate besides symptom control. Our findings support the (tailored) therapy of the elderly and frail patients.

PO-1077 Evaluation of Vascular and Nerve Changes in Nasopharyngeal Carcinoma Patients Following Radiotherapy

M. Da ğ delen 1 , Z. Ş eriko ğ lu Akba ş 2 , C. Barlas 1 , G. Can 3 , C. Arıcı 2 , Ö. Uzel 1

1 Istanbul University- Cerrahpasa, Cerrahpasa Medical Faculty, Department of Radiation Oncology, Istanbul, Turkey; 2 Istanbul University- Cerrahpasa, Cerrahpasa Medical Faculty, Department of Ophthalmology, Istanbul, Turkey; 3 Istanbul University- Cerrahpasa, Cerrahpasa Medical Faculty, Department of Public Health, Istanbul, Turkey Purpose or Objective Radiation-induced optic neuropathy (RION) is one of the most important late complications during head and neck radiotherapy and is recognized usually between 2-9 years after RT. Our study aims to prospectively evaluate retinal and optic disc vascular changes and retinal nerve fiber layer thickness (RNFL) using optical coherence tomography angiography (OCTA) in nasopharyngeal cancer (NPC) patients previously treated with intensity-modulated radiation therapy (IMRT) and with optic nerve doses are above 45 Gy Materials and Methods Fourteen NPC patients and sixteen age-matched healthy control subjects were included in our study. A complete ophthalmological examination including the best-corrected visual acuity (BCVA), intraocular pressure, slit-lamp biomicroscopic, fundoscopic examination, and OCTA were performed for all patients and healthy volunteers. OCTA findings of RT and control groups were compared and correlation analysis was performed to find the association between the radiation-related factors and OCTA findings. Results Inferior hemi disc, parafovea, and perifovea superficial/deep vessel densities were statistically significantly lower in RT patients (Table1). Negative correlations were found between Dmax of the optic tract and both RNFL and vessel densities. Furthermore, there were negative correlations found between the Dmean of globe and vessel densities(Table2).