ESTRO 2023 - Abstract Book

S589

Monday 15 May 2023

ESTRO 2023

CRT was 249.3 mg/m ² . 49 patients (9%) had creatinine clearance less than 60 ml/min, 17 (3%) had AKI grade 3 needing medical intervention. No grade 4 or 5 toxicities were reported. 252 patients required cisplatin dose reduction: 40 patients (8%) due to AKI, 64 patients (12%) due to severe mucositis/vomiting, 56 patients (11%) due to myelosuppression. Conclusion This is a retrospective study of real-world data over a long period of 5 years addressing a dual issue of tolerance and treatment intensity in head and neck cancer patients. The study showed that the proportion of patients developing AKI after cisplatin-based CRT and one week of hydration of only 9% is lower than data found in the literature. The proportion of patients receiving more than 200 mg/m ² is relatively high in our daily practice. This strategy seems to be a cost efficient and very safe method to decrease AKI and optimize the dose intensity of CRT. Home based post-cisplatin hydration could be included in the standard management of head and neck cancer patients receiving concomitant CRT. MO-0719 Chemoradiation in older head-and-neck squamous cell carcinoma patients - A multicenter analysis A. Rühle 1 , S. Marschner 2 , M. Haderlein 3 , A. Fabian 4 , C. Senger 5 , D.R. Dickstein 6 , J. Kraft 7 , J.V.D. Grün 8 , E. Chen 9 , T. Aquino Michaels 9 , J. Domschikowski 4 , A. Bickel 10 , A. Altay-Langguth 8 , V. Lewitzki 7 , K. Ferentinos 11 , S. Schnellhardt 3 , M. Guckenberger 10 , V. Budach 5 , C. Belka 2 , R. Bakst 6 , A. Mayer 12 , A. Grosu 1 , P. Balermpas 10 , C. Stromberger 5 , N.H. Nicolay 1 1 University of Freiburg – Medical Center, Department of Radiation Oncology, Freiburg, Germany; 2 University Hospital, LMU Munich, Department of Radiation Oncology, Munich, Germany; 3 Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Radiation Oncology, Erlangen, Germany; 4 University Hospital Schleswig Holstein, Campus Kiel, Department of Radiation Oncology, Kiel, Germany; 5 Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiation Oncology, Berlin, Germany; 6 Icahn School of Medicine at Mount Sinai, Department of Radiation Oncology, New York, USA; 7 University Hospital Würzburg, Department of Radiation Oncology, Würzburg, Germany; 8 Goethe University Frankfurt, Department of Radiotherapy and Oncology, Frankfurt am Main, Germany; 9 University Hospitals Seidman Cancer Center, Department of Radiation Oncology, Cleveland, USA; 10 University Hospital Zurich, University of Zurich, Department of Radiation Oncology, Zurich, Switzerland; 11 German Oncology Center, European University of Cyprus, Department of Radiation Oncology, Limassol, Cyprus; 12 University Medical Center Mainz, Department of Radiation Oncology and Radiation Therapy, Mainz, Germany Purpose or Objective There is increasing evidence that specific subgroups of elderly patients with head-and-neck squamous cell carcinoma (HNSCC) may benefit from concurrent chemotherapy when treated with definitive radiotherapy. While three-weekly high dose (100 mg/m2) cisplatin is generally considered the standard regimen for definitive chemoradiation, it may result in considerable toxicities in vulnerable older patients; therefore, alternative chemotherapy regimens may be more adequate. The aim of this large multicenter analysis was to examine the oncologic efficacy of different chemotherapy doses and protocols in elderly HNSCC patients. Materials and Methods A total of 677 older ( ≥ 65 years) patients with locoregionally advanced HNSCCs of the oral cavity, oropharynx, hypopharynx or larynx that received definitive chemoradiation between 2005 and 2019 at 12 tertiary cancer centers in Germany, Switzerland, Cyprus and the United States were included in this retrospective analysis. Overall survival (OS), progression free survival (PFS) and locoregional control (LRC) were compared between the different chemotherapy protocols following a pre-registered study protocol (NCT05337631). Results The median age was 71 years (interquartile range [IQR], 68-76 years), the median Charlson Comorbidity Index amounted to 1 point (IQR, 0-3), and 564 patients (83%) had an ECOG performance status of ≤ 1. One-hundred twenty-two patients (18%) exhibited an HPV-positive oropharyngeal carcinoma. Cisplatin (n=298, 44%; 147 [49%] of them receiving cisplatin 30-40 mg/m2 weekly), cisplatin/5-FU (n=137, 20%), carboplatin (n=68, 10%) and mitomycin C/5-FU (n=64, 9%) were the most commonly applied chemotherapy regimens. The median cisplatin dose of patients receiving single-agent cisplatin amounted to 175 mg/m2 (IQR, 120-200 mg/m2). Cisplatin doses of ≥ 200 mg were associated with significantly increased OS, PFS and LRC (all p <0.05, log-rank test) compared to cumulative doses <200 mg. Beyond 200 mg/m2, no additional benefit could be elucidated for higher cisplatin doses ( p =0.067 for OS, p =0.095 for PFS, p =0.340 for LRC). There was no difference in terms of OS ( p =0.135), PFS ( p =0.523) or LRC ( p =0.948) in patients receiving multi-agent chemotherapy compared to patients treated with cisplatin only. Carboplatin (±5-FU or docetaxel or paclitaxel) was associated with significantly diminished PFS ( p <0.05) and LRC ( p <0.05) in comparison to single-agent cisplatin regimens, while OS was comparable ( p =0.597). Conclusion This analysis based on a multicenter study suggests that a minimum cumulative cisplatin dose of 200 mg/m2 should be pursued also in older adults with HNSCC undergoing definitive chemoradiation; however, there seems to be no or little benefit of higher doses beyond 200 mg/m2. There are indications of reduced efficacy of carboplatin compared to cisplatin regimens, suggesting that cisplatin should not be generally replaced by carboplatin in older cisplatin-eligible HNSCC patients.

Mini-Oral: Radiobiology

MO-0720 Proton FLASH: Impact of dose rate on biological response in an acute damage mouse model P. Poulsen 1 , E. Kanouta 1 , M. Sitarz 1 , C. Ankjærgaard 2 , J. Johansen 1 , C. Andersen 2 , C. Grau 1 , B. Sørensen 3 1 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark; 2 Technical University of Denmark, DTU Health Tech, Roskilde, Denmark; 3 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark

Purpose or Objective