ESTRO 2023 - Abstract Book

S397

Sunday 14 May 2023

ESTRO 2023

Conclusion The compression belt achieves a stable set-up for liver patients and over 97% of patients can tolerate it. Almost 1/3 of interfraction shifts are greater than 10mm. This is not concerning for patients provided shifts are corrected with imaging and our centre will continue to CBCT daily. Larger ∑ in the long were seen in patients with no EBH scan and in patients with a higher BMI. Intrafraction errors were low (<2mm), highlighting the compression belt is a good solution for maintaining a stable position during treatment delivery. Thus, the post-treatment CBCTs were removed after 10 patients ensuring IGRT doses are ALARP. The interobserver variability was low, but although matches were performed independently, they were not completed blind from online registrations. This may have increased match agreement. The initial findings in Table 2 indicate treatment uncertainties are low and our CTV-PTV margin of 5mm appears suitable when using the compression belt in liver patients with daily CBCT; however, more patients in the analysis are required for conclusive PTV calculations. PD-0489 Retinopathy and optic neuropathy after radiotherapy for brain, head and neck tumor:systematic review B. Kinaci-Tas 1 1 Leiden University Medical Center, Radiotherapy, Leiden, The Netherlands Purpose or Objective Remarkable progress has been made with respect to the visualization of tumors for treatment planning purposes and the application of highly accurate radiation dose delivery. However, it is still inevitable that the eye and optic tract may receive a significant radiation dose that exceeds its normal tissue tolerance dose. Depending on the extent of involvement of the eye and optic tract in the radiation field, variable acute and late ocular damage may occur. Retinopathy and optic neuropathy are relatively common late ocular toxicities of radiation therapy for tumors arising in the brain, head and neck. Both can have important clinical consequences that may contribute significantly to a deterioration of the patient’s quality of life. Patients present mainly with visual symptoms that may include partial or complete loss of vision and visual field defects. Accurate estimation of the prevalence of retinopathy and optic neuropathy after radiation therapy in patients with brain, head and neck tumors, in relation to the administered radiation dose is lacking. The aim of this study was to systematically review the prevalence of retinopathy and optic neuropathy in patients undergoing radiation therapy for brain, head and neck tumors. Further, we aimed to evaluate the effect of both radiation dose and the patient characteristics on the occurrence of retinopathy and optic neuropathy. Materials and Methods The PubMed, Embase, and Cochrane Library databases were searched for articles reporting the prevalence of retinopathy and optic neuropathy in patients undergoing radiation therapy for brain, head and neck tumors. The primary outcome was the pooled prevalence of retinopathy and optic neuropathy. The secondary outcome consisted of the effect of the total radiation dose prescribed to the tumor on the occurrence of retinopathy and optic neuropathy. Furthermore, we aimed to evaluate the radiation dose parameters to the tumor, retina, optic nerve and chiasm on the occurrence of retinopathy and optic neuropathy. Results Seventy- eight publications were selected describing a total of 11279 patients (mean age 51 years and a mean follow-up of 57 months). The pooled prevalence was 3.8%. No retinopathy was reported for a prescribed dose to the tumor that is less than 50Gy (Figure 1). The prevalence of optic neuropathy was higher for a prescribed dose to the tumor at >50Gy compared to a prescribed dose to the tumor at <50Gy (Figure 2). We observed a higher prevalence rate for retinopathy (6.0%) compared to the prevalence of optic neuropathy (2.0%). Insufficient data on organs at risk dose is reported, making it impossible to establish a more detailed dose-response relationship.