ESTRO 2022 - Abstract Book

S737

Abstract book

ESTRO 2022

An expression was derive to employ calibrated radiochromic films with low-energy protons taking LET quenching into account. The final relative error in RE using our models for a given beam energy and air gap ranges between 2% and 20%.

Poster Discussion: 20: Head and neck

PD-0817 IL-6 as surrogate marker for PET-detected tumor hypoxia dynamics in head-and-neck cancer patients

N.H. Nicolay 1 , A. Rühle 1 , N. Wiedenmann 1 , J. Fennell 1 , M. Mix 2 , J. Ruf 2 , R. Stoian 1 , A.R. Thomsen 1 , P. Vaupel 1 , D. Baltas 1 , A. Grosu 1 1 University of Freiburg - Medical Center, Department of Radiation Oncology, Freiburg, Germany; 2 University of Freiburg - Medical Center, Department of Nuclear Medicine, Freiburg, Germany Purpose or Objective Intratumoral hypoxia is known to increase radioresistance of head-and-neck squamous cell carcinoma (HNSCC). [ 18 F]FMISO PET imaging is able to non-invasively display and monitor tumor hypoxia; however, it requires considerable logistic efforts, especially if performed in radiotherapy treatment position. We therefore aimed to explore the role of dynamic interleukin- 6 (IL-6) plasma levels as a potential endogenous blood-based biomarker to monitor tumor hypoxia in HNSCC patients. Materials and Methods Twenty-seven HNSCC patients undergoing definitive cisplatin-based chemoradiation within a prospective trial (DRKS00003830) had stored blood samples available that were analyzed regarding their plasma IL-6 levels at several time points during chemoradiation. The intratumoral hypoxic subvolume (HSV) was quantified in treatment weeks 0, 2 and 5 of chemoradiation using [ 18 F]FMISO PET/CT imaging. Pearson’s correlation analyses were performed in order to assess the association between IL-6 plasma levels and PET-based hypoxia. A multiple regression analysis including several patient- and tumor-related factors was used to reveal potential confounder variables for the association between both parameters. Furthermore, the diagnostic power of IL-6 in terms of early tumor hypoxia response prediction was investigated with receiver-operating characteristic (ROC) analyses. Cox analyses were performed to study the impact of IL-6 levels on the progression-free (PFS) and overall survival (OS). Results Mean IL-6 plasma concentrations ranged at 15.1, 19.6 and 31.0 pg/mL in weeks 0, 2 and 5 of chemoradiation, respectively. IL-6 plasma levels strongly correlated with the intratumoral HSV at all analyzed time points (week 0: r=0.775, p <0.001, week 2: r=0.553, p =0.007, week 5: r=0.734, p <0.001). Additionally, IL-6 levels in week 2 were found significantly higher in patients with missing early tumor hypoxia response within the first two treatment weeks ( p =0.016) and could predict early hypoxia response with an AUC of 0.822 ( p =0.031). Persistence of elevated IL-6 levels in week 5 corresponded to a decrease in PFS (HR=1.013, p =0.078) and OS (HR=1.018, p =0.013). Conclusion IL-6 plasma levels correlated with [ 18 F]FMISO PET-detected intratumoral hypoxia in HNSCC patients. Furthermore, IL-6 was able to predict early hypoxia response during chemoradiation. Following external validation, IL-6 may serve as an endogenous blood hypoxia marker that could be used for hypoxia-based personalized radiotherapy concepts. A. Rühle 1 , A. Grosu 1 , N. Wiedenmann 1 , J. Ruf 2 , R. Stoian 1 , A.R. Thomsen 1 , E. Gkika 1 , W. Weber 3 , D. Baltas 1 , M. Mix 2 , N.H. Nicolay 1 1 Medical Center – University of Freiburg, Department of Radiation Oncology, Freiburg, Germany; 2 Medical Center – University of Freiburg, Department of Nuclear Medicine, Freiburg, Germany; 3 Technical University of Munich, Department of Nuclear Medicine, Munich, Germany Purpose or Objective Intratumoral hypoxia is known to deteriorate the oncological outcome of head-and-neck squamous cell carcinoma (HNSCC) patients receiving radiotherapy. Plasma hypoxia markers could potentially be used as biomarkers to monitor tumor- associated hypoxia; however, the exact correlation between plasma hypoxia markers and imaging-based intratumoral hypoxia is yet not fully understood. We therefore aimed to examine the value of established and novel hypoxia-associated plasma proteins as potential surrogate markers for tumor hypoxia. Materials and Methods Within a prospective imaging trial (DRKS00003830), serial blood samples of 27 HNSCC patients receiving definitive cisplatin- based chemoradiation were collected and analyzed for osteopontin, galectin-3, vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) plasma concentrations using enzyme-linked immunosorbent assays. The intratumoral hypoxic subvolume (HSV) was quantified in treatment weeks 0, 2 and 5 based on [ 18 F]FMISO PET/CT. The association between plasma hypoxia markers and PET-defined hypoxia was assessed using Pearson’s correlations, and receiver-operating characteristic (ROC) analyses were performed to determine the prognostic power of the plasma hypoxia markers. PD-0818 Association between plasma hypoxia markers and tumor hypoxia in head-and-neck cancer patients

Results