ESTRO 2023 - Abstract Book

S1288

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ESTRO 2023

Symptom relief was achieved in all but 1 patient (91%). 27% of patients presented G1-2 fatigue and no other side effects.

Conclusion The PATHY-radiotherapy was effective, safe and well tolerated treatment. It resulted in improvement in symptoms and quality of life of highly complex patients without associated treatment related toxicity. This approach showed high immunogenic potential resulting in varying degrees of tumor downsizing/neoadjuvant effect with average tumor shrinkage corresponding to 60%. Optimum patient selection and definition of most suitable disease characteristics are currently explored in an ongoing, prospective study.

PO-1587 two years of ocular proton therapy in The Netherlands, clinical results

C. Rasch 1 , P. Bakker 2 , M. Rodrigues 2 , M. Marinkovic 3 , K. Vu 3 , J. Bleeker 4 , C. van Rij 5 , E. Kilic 6 , J. Beenakker 7 , N. Horeweg 8 , G. Luyten 3 1 LUMC, Radiation Oncology, Leiden, Nauru; 2 Holland Proton Therapy Center, Radiotherapy, Delft, The Netherlands; 3 Leiden University Medical Center, Ophthalmology, Leiden, The Netherlands; 4 Leiden University medical Center, Ophthalmology, Leiden, The Netherlands; 5 Erasmus Medical Center, Radiation Oncology, Rotterdam, The Netherlands; 6 Erasmus Medical Center, Ophthalmology, Rotterdam, The Netherlands; 7 Holland Proton Therapy Center, Radiology, Delft, The Netherlands; 8 Leiden University Medical Center, Radiation Oncology, Leiden, The Netherlands Purpose or Objective Uveal Melanoma is a rare cancer with a rising incidence of 143 in 1990 to 239 in 2019 in the Netherlands. Local treatment consists of brachytherapy, external beam radiotherapy (proton or photon) or enucleation. Most patients are treated locally with ruthenium brachytherapy (+/- 102 /year) but those with a tumor prominence of >7mm, and/or a basal diameter >16 mm and/or involvement of the optic disc (> ⅓ of the circumference) are referred for proton therapy. Proton Therapy for Ocular Melanoma is available in The Netherlands from Jan 2020 onwards. The purpose of this abstract is to evaluate the first two-year results. Materials and Methods All consecutive patients treated with proton therapy for Uveal Melanoma from Jan 2020 till December 31st 2021 were included in this evaluation (n=56). Pre-treatment imaging consists of ultrasound and 3Tesla MRI, followed by operative placement of tantalum clips on the sclera at the edge of the tumor and post-operative MRI. Proton treatment is performed with a dedicated passive scattered beam using an individual mold in the Eye Treatment Room at the Holland Particle Center (Delft, The Netherlands). The prescribed dose is 4x15 (Cobalt Equivalent) Gy on four consecutive days. Treatment planning is performed in Eclipse Ocular Proton Planning (EOPP, Varian Medical Systems, Palo Alto). Patients have regular FU in the referring center (LUMC or ErasmusMC). Time to event analyses were conducted according to the Kaplan-Meier method. Results 56 patients with a median FU of 1 year were included in this study. The median age was 64 years. The tumors were central 12 (21%), midperipheral 29 (52%) and peripheral 15 (27%). Nineteen (34%) had a juxtapupillary location. Tumor stage: T1 5 (9%), T2 12 (21%), T3 32 (57%), T4 7 (13%). Retinal detachment before treatment was present in 42 cases (75%). Tumor regression was slow and continued across the FU period (Fig.1). At two years, Overall Survival was 86% (T1-2 100%, T3-4