ESTRO 2020 Abstract book

S347 ESTRO 2020

We randomized 100 patients of histopathologically proven primary head-and-neck cancer into ART and non-ART arms. Target/OAR delineation was done after CT simulation following rigid immobilization. All patients were started treatment with VMAT & image guidance. After treatment started, patients were re-simulated using CT imaging again at 3rd, 5th and 7th week. Predefined adaptive re- contouring workflow using deformable image registration was applied to generate adaptive plan. For patients in ART Arm, the new plan was executed for the remaining fractions. In Non ART Arm, treatment was continued as per the original plan. All the patients were observed for total volume of parotid glands at week 1, 3, 5 and 7. RTOG Toxicity Criteria was used to observe sub-acute and late toxicity reactions with regards to dermatitis, mucositis, xerostomia and laryngral toxicity in both arms at week 3 rd and 6 th month post treatment. Results The percentage volume change in parotid glands was observed to be 6.25%, 16.37% and 28.39% in adaptive arm and 11.53%, 23.54% and 32.56% in non adaptive arm at 3, 5 and 7 weeks (P-value 0.009 and 0.012 at 3rd and 5th wk respectively). On clinical examination Grade 1 or higher dermatitis was seen in 54% and 6% in adaptive arm whereas in 71% and 20% in non-adaptive arm (P-value 0.036 at 3 months). The patients having grade 1 or higher xerostomia in adaptive arm at 3 and 6 months were 62% and 46% and in non-adaptive arm was 67% and 36% at 3 and 6 months respectively (p-value 0.014 at 6 months). Patients in both arms were comparable in terms of mucositis reactions at both 3 rd and 6 th month of follow up. (48%,23% in ART and 46%,20% in non-ART). Both groups were comparable in terms of sub-acute and late laryngeal toxicity. Conclusion Volume changes in parotid glands and gross tumour is observed throughout the course of radiation treatment and ART can aid in better sparing of parotid glands with an advantage over non-ART in terms of reduced late xerostomia and dermatitis. Though ART requires increased man hours, in carefully selected patients it improves the therapeutic ratio of treatment. 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 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 protocol which incorporated the gross tumour volume with