ESTRO 2020 Abstract Book

S320 ESTRO 2020

signature). This was confirmed in multivariable Cox regression including age and T stage. In the xenograft models, the gene signatures based on cancer stem cell markers, hypoxia and radiosensitivity showed a significant association with TCD50 (figure B).The correlations between these three gene signatures were weak (R<0.2).

had tumors in advanced stages (T3/4 stage, n=132/207, 64%). 31% of the patients were irradiated for a macroscopic tumor disease (n=65/207). Overall, 15% received primary (n=31/207) and 85% postoperative RT (n=176/207). Additionally, toxicity was assessed according to the Common Toxicity Terminology Criteria for Adverse Events (CTCAE) v5. Results Median follow-up was 50 months. At last follow up, 84% of the patients were still alive (n=174/207) while local recurrence occurred in 12% (n=25/207) and distant relapse in 27% (n=56/207). Estimated 5-year and 10-year LC, OS and DPFS rates were 84% and 69% for LC, 83% and 73% for OS, 62% and 44% for DPFS, respectively. In univariate and multivariate analysis, we could identify two prognostic subgroups; one subgroup resulting in decreased LC rates and another subgroup having a survival disadvantage in OS and DPFS. While patients with a macroscopic tumor disease (yes vs. no; p=0.01, HR 5.31, 95%-CI 1.95-14.51) and tumors of upper T stage (T1-4; p=0.03, HR 1.58, 95%- CI 1.03-2.43) showed significantly more local relapses, the worst survival outcome was observed for patients with tumors of upper T stage (p<0.01, HR 2.98, 95%-CI 1.59-5.59 for OS; p=0.02, HR 1.90, 95%-CI 1.08-3.32 for DPFS) and solid histology (p=0.02, HR 2.82, 95%-CI 1.22-6.55 for OS; p<0.01, HR 0.93, 95%-CI 0.06-0.58 for DPFS). Toxicity was moderate with 19% late grade 3 toxicity. Conclusion The authors conclude that bimodal RT results in superior LC rates with moderate toxicity. In multivariate analysis, upper T stage and the existence of a macroscopic tumor were identified as major prognostic factors affecting LC negatively. OC-0573 Improvement in late dysphagia following clinical target volume reduction in the De-ESCALaTE study C.T.K. Fong 1 , P. Mistry 2 , T. Roques 3 , M. Evans 4 , H.Q. Yang 5 , L. O'Toole 6 , P. Sanghera 1 , C. Nutting 7 , B. Foran 8 , M. Sen 9 , H. Al Booz 10 , T. Fulton-Lieuw 11 , M. Dalby 2 , J. Dunn 2 , A. Hartley 1 , H. Mehanna 11 1 Hall-Edwards Radiotherapy Research Group, Queen Elizabeth Hospital, Birmingham, United Kingdom ; 2 University of Warwick, University of Warwick, Coventry, United Kingdom ; 3 Norfolk and Norwich University Hospitals, Oncology, Norwich, United Kingdom ; 4 Velindre Hospital, Oncology, Cardiff, United Kingdom ; 5 Cambridge University Hospital NHS Foundation Trust, Oncology, Cambridge, United Kingdom ; 6 Castle Hill Hospital, Oncology, Cottingham, United Kingdom ; 7 Royal Marsden Hospital, Oncology, London, United Kingdom ; 8 Weston Park Hospital, Oncology, Sheffield, United Kingdom ; 9 St James’s Institute of Oncology, Oncology, Leeds, United Kingdom ; 10 Bristol Haematology and Oncology Centre, Oncology, Bristol, United Kingdom ; 11 Institute of Head and Neck Studies and Education InHANSE, University of Birmingham, Birmingham, United Kingdom Purpose or Objective The De-ESCALaTE study showed an overall survival advantage for the administration of synchronous cisplatin chemotherapy with radiotherapy in low risk oropharyngeal cancer when compared with synchronous cetuximab. During the trial, a radiotherapy quality assurance (RTQA) protocol amendment permitted centres to swap from the original radiotherapy contouring protocol (incorporating the whole oropharynx into the high dose clinical target volume (CTV) (anatomical protocol)), to a

Conclusion In our study, we successfully transferred gene signatures that were developed for patients with locally advanced HNSCC treated mainly by pRCTx to a patient cohort treated by PORT-C. Furthermore, cancer stem cell markers, hypoxia-associated genes and a radiosensitivity signature were able to stratify xenografts with respect to the TCD50. Since these signatures were weakly correlated, they may be considered as independent and robust biomarkers for future personalized radiotherapy of patients with locally advanced HNSCC. References: [1] Linge et al. Radiother Oncol 121: 364 (2016). [2] Shen et al. Oncol Rep 83: 3403 (2017).

[3] Toustrup et al. Cancer Res 71: 5923 (2011). [4] Kim et al. BMC Genomics; 13: 348 (2012). [5] Chung et al. Cancer Res; 66: 8210 (2006).

OC-0571 Clinical Impact of Adaptive Radiotherapy in Head and neck Cancer – A Randomized controlled trial

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OC-0572 Treatment outcome of 207 patients with adenoid cystic carcinoma of the major salivary glands. S. Akbaba 1 , T. Bostel 2 , J. Hoerner-Rieber 1 , N. Nicolay 3 , T. Forster 1 , T. Held 1 , K. Lang 1 , S. Adeberg 1 , J. Debus 1 1 Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany ; 2 Mainz University Hospital, Radiation Oncology, Heidelberg, Germany ; 3 Freiburg University Hospital, Radiation Oncology, Freiburg, Germany Purpose or Objective We aimed to evaluate treatment outcome of combined radiotherapy (RT) including photon intensity modulated radiotherapy (IMRT) and carbon ion boost for 207 adenoid cystic carcinomas (ACC) of the major salivary glands, one of the currently available largest single-center patient collectives for this cohort. Material and Methods 207 patients who received IMRT with photons combined with carbon ion boost (bimodal RT) for ACC of the major salivary glands at the Department of Radiation Oncology, Heidelberg University Hospital and at the Heidelberg Ion- Beam Therapy Center (HIT) between 2009 and 2019 were analyzed retrospectively for local control (LC), distant progression-free survival (DPFS) and overall survival (OS) using Kaplan-Meier estimates. The majority of patients