ESTRO 2022 - Abstract Book

S925

Abstract book

ESTRO 2022

Conclusion Pts with LAOPCs treated with modern techniques experienced a favorable toxicity profile regardless the treatment approach . A higher proportion of G3 weight loss was found in the curative IMRT cohort compared to the TORS cohort. This finding could probably due to the presence of macroscopic disease which could cause mechanic dysphagia, the higher rate of advanced primary tumor stage and concurrent chemotherapy in this group of pts compared to those treated with TORS.

PO-1089 Antibiotic use goes along with reduced survival in head-and-neck cancer patients after radiotherapy

J. Zou 1 , I. Popp 1 , M. Glaser 1 , L. Halle 1 , S.K. Spohn 1 , E. Gkika 1 , C. Zamboglou 1 , A. Knopf 2 , A. Grosu 1 , N.H. Nicolay 1 , A. Rühle 1

1 Medical Center – University of Freiburg, Department of Radiation Oncology, Freiburg, Germany; 2 Medical Center – University of Freiburg, Department of Otorhinolaryngology, Freiburg, Germany Purpose or Objective Pre- and peritherapeutic antibiotics administration has been shown to negatively impact the oncological outcome of melanoma and lung cancer patients receiving immune checkpoint inhibitors, possibly by affecting the microbiome-immune system-cancer axis. We therefore aimed to explore the effects of antibiotic application on the outcomes of head-and-neck squamous cell carcinoma (HNSCC) patients undergoing definitive (chemo)radiotherapy [(C)RT]. Materials and Methods In this single-center retrospective study, a cohort of 220 HNSCC patients who were treated with (C)RT between 2010 and 2019 was evaluated. Information about antibiotics application including indication, duration and drug classes were collected from electronic patient records. Patient and treatment characteristics were compared depending on antibiotic usage with t-tests and chi-square tests. The influence of antibiotics administration on progression-free (PFS) and overall survival (OS) was determined with Kaplan-Meier analyses. Results A total of 154 patients (70%) received antibiotics in a time interval ranging between 30 days before (C)RT until treatment completion. ECOG status, age, N stage, radiotherapy dose and radiotherapy completion rate showed no differences between patients with and without antibiotics treatment, whereas patients who received antibiotics exhibited higher T stages and more often underwent RT instead of CRT. While 93 patients (42%) obtained antibiotics during the 30 days prior to (C)RT