ESTRO 2021 Abstract Book

S399

ESTRO 2021

Incidence of ≥grade 2 of laryngeal edema and voice change were 1.7%/0.5% and 9.3%/5.4% in SF/Ax groups, respectively. The late adverse event at 8 years of SF/Ax group was 11.9%/7.4%, respectively. Late adverse event of Ax group showed favorable tendency compared to Sx group (HR 0.529, 95% CI 0.278-1.007, p=0.055). As for CNSI of ≥grade 2, 4.1%/1.1%/2.7% was observed in SF/Ax/entire group. Conclusion In this long follow-up analysis, Ax group remained slightly favorable efficacy with tendency for lower incidence of late adverse event including CNSI compared to SF group. With relatively long follow-up data, Ax was comparable to SF in efficacy and safety. Accelerated fractionated regimen may be suitable for early GC because of its convenience in sparing treatment time, cost, and labor. OC-0515 NBTXR3 activated by radiotherapy in cisplatin-ineligible locally advanced HNSCC patients C. Le Tourneau 1 , V. Calugaru 2 , Z. Takacsi-Nagy 3 , X. Liem 4 , Z. Papai 5 , V. Moreno 6 , I. Braña 7 , S. Salas 8 , G. Poissonnet 9 , E. Calvo 10 , B. Doger 11 , O. Choussy 12 , X. Mirabel 13 , S. Krhili 14 , K. Bernois 15 , N. Fakhry 16 , S. Wong Hee Kam 17 , E. Borcoman 18 , C. Hoffmann 12 1 Institut Curie, Drug Development and Innovation (D3i), Paris , France; 2 Institut Curie, Radiation therapy, Paris, France; 3 National Institute of Oncology, Center of Radiotherapy, Budapest, Hungary; 4 Oscar Lambret Cancer Center, Radiotherapy-Brachytherapy, Lille, France; 5 Medical Centre, Hungarian Defense Forces, Oncology, Budapest, Hungary; 6 START - Fundación Jiménez Díaz, Phase I Clinical Trials Unit, Madrid, Spain; 7 Val d’Hebron Institut of Oncology, Early Clinical Drug Development Group, Barcelona, Spain; 8 Hôpital Timone, Medical Oncology-Palliative Care Service, Marseille, France; 9 Unicancer - Antoine Lacassagne Center, Cervico-Facial Oncological Surgery, Nice, France; 10 START - Hospital Sanchinarro, Medical Oncology Service, Madrid, Spain; 11 START - Fundación Jiménez Díaz , Medical Oncology Service, Madrid, Spain; 12 Institut Curie, Department of surgical oncology, Paris, France; 13 Oscar Lambret Cancer Center, Department of Radiotherapy- Brachytherapy, Lille, France; 14 Institut Curie, Department of Radiation therapy, Paris, France; 15 Nanobiotix, Biometry, Paris, France; 16 Hôpital Timone, ENT and Cervico Facial Surgery Service, Marseille, France; 17 Hôpital Timone , Radiation Oncology, Marseille, France; 18 Institut Curie, Drug Development and Innovation (D3i), Paris, France Purpose or Objective Concurrent radiotherapy (RT) with high-dose cisplatin, or cetuximab in case of intolerance to cisplatin, are the non-surgical standard treatment for locally advanced head and neck squamous cell carcinoma (LA HNSCC). However, elderly patients, patients with poor performance status, comorbidities, and/or intolerance may not benefit from these treatments and represent a high unmet medical need. New approaches are thus needed to improve patient clinical outcomes without adding toxicity. NBTXR3, composed of functionalized hafnium oxide nanoparticles , is injected intratumorally and activated by RT. NBTXR3 increases the RT energy deposit inside tumor cells and subsequently increases tumor cell death compared to RT alone, without adding toxicity to healthy tissues. Here we present current results of the dose expansion part of the phase I study evaluating NBTXR3 plus intensity modulated radiation therapy (IMRT) in this population. Materials and Methods Patients with stage III-VA or T3/T4 (AJCC/UICC TNM staging system 8th ed.) HNSCC of the oropharynx or oral cavity, ineligible to cisplatin or cetuximab and amenable for RT, received a single intratumoral injection of NBTXR3 and IMRT (70 Gy in 35 fractions /7 weeks) [ NCT01946867]. A classical 3 + 3 dose escalation design has tested four doses of NBTXR3, equivalent to 5, 10, 15, and 22% of baseline theoretical tumor volume. The RP2D established as 22% of baseline tumor volume is further tested in the dose expansion part of the study. The primary endpoints of the dose expansion part are objective response rate (ORR) and complete response rate (CRR) of the primary tumor, by imaging according to RECIST v1.1. Safety is also evaluated. Results As of August 13, 2020, 43 patients have been treated in the dose expansion part of the study. The median age was 70.7 years old (range: 50.7- 89.9), 70% of patients had cardiac disorder risk, 44% had gastrointestinal disorder risk and 44% metabolic and nutrition disorder risk. The median tumor volume was 42.8 mL (range: 1.3 - 222.3). In the evaluable population for efficacy (N=31), the ORR of the primary lesion was 83.9% and the CRR 67.7% at a median time of 7.8 months after NBTXR3 injection. Three patients (7%) experienced at least one serious adverse event (AE) related to the injection procedure and/or NBTXR3 which represented less than 1% of all reported AEs. RT-related toxicity was as expected with IMRT. Three deaths due to AEs related to RT and other causes were reported. Recruitment is ongoing and updated efficacy and safety results will be presented. Conclusion NBTXR3 intratumoral administration followed by IMRT may represent an option in elderly in elderly patients or patients with multiple comorbidities with LA-HNSCC who have limited therapeutic options. NBTXR3 activated by RT showed promising anti-tumor efficacy, supporting further evaluation in a phase III randomized trial. OC-0516 Local control in HNSCC after introduction of geometric margins in DAHANCA radiotherapy guidelines R. Zukauskaite 1,2 , J. Grau Eriksen 3,4 , E. Andersen 5 , J. Johansen 1 , E. Samsøe Hinsby 5,6 , S. Long Krogh 7 , J. Overgaard 4 , C. Grau 3,8 , C. Rønn Hansen 2,7,8 1 Odense University Hospital, Department of Oncology, Odense, Denmark; 2 University of Southern Denmark, Department of Clinical Research, Odense, Denmark; 3 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 4 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 5 Copenhagen University Hospital Herlev, Department of Oncology, Copenhagen, Denmark; 6 Zealand University Hospital, Department of Oncology, Naestved, Denmark; 7 Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark; 8 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark