ESTRO 2023 - Abstract Book

S280

Sunday 14 May 2023

ESTRO 2023

Materials and Methods Twenty-eight AYAs (15-39 years) with HNSs treated between January 2001 and July 2021 at our institution were included in our analysis. Patients with skull-base tumors and mixed treatment with photons were excluded. The median age was 21.6 years (range, 15 - 37.9). Rhabdomyosarcoma (39.3%), Ewing sarcoma (17.9%), Chondrosarcoma (14.3%) and Osteosarcoma (14.3%) were the most frequent diagnosis. The median tumor at diagnosis was 42.5 mm (range, 12 - 95). Three (10.7%) patients were metastatic before the PBSPT. Five (17.9%) had a complete tumor resection, 11 (39.3%) a R1 resection, 4 (14.3%) a R0 resection and 8 (28.6%) had only a biopsy. The median total radiation dose was 63 Gy (RBE) (range, 45 - 74) delivered in a median dose per fraction of 1.8 Gy (RBE) (range, 1.8 - 2.2). Three (10.7%) patients were reirradiated. Thirteen (46.4%) received concomitant chemotherapy. Toxicity was reported according to Common Terminology Criteria for Adverse Events (CTCAE 5.0). Survival was estimated using the Kaplan–Meier method. Results With a median follow-up of 57 months (range, 37 – 243), 4 patients (14.3%) had local failure only, 2 (7.1%) experienced distant failure only and 2 (7.1%) had local and distant failure. The estimated actuarial 5-year local control (LC) was 71.8% (Fig. 1A). Median time to local failure (LF) was 13.4 months. Three (10.7%) patients died, all of them from their cancer. Estimated 5-year overall survival (OS) was 90.9% (Fig. 1B). Six (21.4%) patients developed non-ocular grade ≥ 3 toxicity, which consisted of otitis media (n=2), hearing impairment (n=2), osteoradionecrosis (n=1) and sinusitis (n=1). Four (14.3%) patients developed cataract that required surgery. The 5-year freedom from non-ocular grade 3 toxicity was 91.1% (Fig. 1C). Median time to grade 3 toxicity was 66.1 months. No grade 4 or more toxicity was observed.

Conclusion Excellent clinical outcomes with acceptable late toxicity rates were observed for AYAs with HN sarcomas after PBSPT.

MO-0380 Proton pencil beam scanning in pediatric posterior fossa tumors: a European treatment planning study L. Toussaint 1 , L. Muren 1 , F. Cerron Campoo 2 , F. Charlwood 3 , M. Fager 4 , A. Goedgebeur 5 , F. Goudjil 6 , I. Kristensen 7 , P. Laegdsmand 1 , A. Mirandola 8 , C. Moignier 9 , E. Petterson 10,11 , S. Plaude 12 , R. Righetto 13 , A. Vestergaard 1 , W. Matysiak 14 1 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark; 2 Proton Therapy Center Quirónsalud, Department of Radiation Oncology, Madrid, Spain; 3 The Christie NHS Foundation Trust, Medical Physics and Engineering, Manchester, United Kingdom; 4 Karolinska University Hospital, Department of Medical Radiation Physics, Stockholm, Sweden; 5 Particle UZ Leuven, Department of Radiation Oncology, Leuven, Belgium; 6 Institut Curie, Department of Radiation Oncology, Paris, France; 7 Skane University Hospital, Department of Hematology, Oncology and Radiation Physics, Lund, Sweden; 8 CNAO National Center for Oncological Hadrontherapy, Department of Radiation Oncology, Pavia, Italy; 9 Centre Regional Francois Baclesse, Department of Radiation Oncology, Caen, France; 10 Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Department of Medical Radiation Sciences, Gothenburg, Sweden; 11 Sahlgrenska University Hospital, Department of Therapeutic Radiation Physics, Medical Physics and Biomedical Engineering, Gothenburg, Sweden; 12 Essen University Hospital, West German Proton Therapy Centre Essen (WPE), Essen, Germany; 13 Trento Proton Therapy Center, Department of Radiation Oncology, Trento, Italy; 14 University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands Purpose or Objective Radiation-induced brainstem/spinal injury is of great concern in the treatment of posterior fossa (PF) tumors. However, there are currently no recommendations on treatment planning ‘best-practice’ for pencil beam scanning (PBS) proton