ESTRO 38 Abstract book

S640 ESTRO 38

DMFS of IPTW-adjusted cohort were 77.9%, 51.7%, 81.9%, 53.6% (definitive RT) and 86.8%, 48.9%, 79.9%, 53.7% (surgery + PORT). Conclusion Two analyses using PS showed there were no differences in treatment outcomes after balancing patient characteristics. Definitive RT would actually give better treatment results than those reported in previous studies. These results ultimately need be explored in a randomized trial. EP-1155 Rare entities in head-and-neck cancer: A single institutional experience of carbon-ion reirradiation T. Held 1 , P. Windisch 1 , S. Akbaba 1 , K. Lang 1 , D. Bernhardt 1 , P. Plinkert 2 , S. Kargus 3 , K. Freier 3 , S. Rieken 1 , K. Herfarth 1 , J. Debus 1 , S. Adeberg 1 1 Heidelberg University Hospital, Department of Radiation Oncology, Heidelberg, Germany ; 2 Heidelberg University Hospital, Department of Otorhinolaryngology- Head and Neck Surgery, Heidelberg, Germany ; 3 Heidelberg University Hospital, Department of Oral and Maxillofacial Surgery, Heidelberg, Germany Purpose or Objective The objective of this investigation was to evaluate outcome and toxicity of carbon-ion reirradiation (CIR) in patients with rare tumor entities of head-and-neck cancer. There are no guidelines for the treatment of these indications, therefore we want to increase the body of evidence. Material and Methods Thirty-two consecutive patients with infrequent head- and-neck cancer entities treated at our clinic between 2010 and 2017 were retrospectively analyzed regarding progression free survival (PFS), overall survival (OS), patterns of failure and toxicity. Acute (initial 90 days after CIR) and late toxicity were assessed using NCI CTCAE v4.03. Results The median age prior to CIR was 63 years (range 27 – 79 years) and the median time between initial irradiation and CIR was 5.2 years (range 0.6 – 46.5 years). On average, patients received 4 (range 1 – 6) tumor-specific treatments before CIR. 22% of primary tumors were mucoepidermoid carcinomas, 19% were acinar cell carcinomas, 16% were esthesioneuroblastomas, 13% were lymphoepithelial carcinomas and 9% myoepithelial carcinomas. Other entities included sinonasal undifferentiated carcinoma, salivary duct carcinoma and neuroendocrine carcinoma. Most common tumor sites were salivary glands (47%), nasopharynx (22%) and paranasal sinus (19%). 28 patients (87.5%) had T4-tumors and 4 patients (12.5%) had distant metastases prior to CIR. The median PTV and CTV of CIR were 137.1 ccm (range 23.1 – 714.89 ccm) and 98.3 ccm (range 13.3 – 550.6 ccm) respectively. Patients received a median dose of 51 Gy (RBE) (range 36 – 66 Gy (RBE)) in 3 Gy (RBE) fractions and the median cumulative applied dose after CIR was 128.6 BED 2Gy (range 105.8 – 146.5 BED 2Gy). 22% underwent surgical resection prior to CIR. Median overall survival after CIR was 24.1 months (95% CI 16.1 – 32.0 months). 11 patients (34%) survived at least 2 years after CIR. Local and distant control one year after CIR were 66% and 72% respectively. 92% of local recurrences after CIR were in-field. Patients with tumors infiltrating the skull base had a significantly worse OS compared to patients with salivary gland tumors (p=0.012). In addition, patients with two prior irradiation treatments compared to one prior course of radiation therapy had a significantly worse OS (p=0.001). No serious acute or late toxicity (≥ grade 3) after CIR was observed. Late toxicities of grade 2 included middle ear inflammation (n=3; 9.4%), dysgeusia (n=3; 9.4%), trismus (n=3; 9.4%) and impaired hearing (n=3; 9.4%). 18 months

Conclusion Approximately, 3/4 th of the patients of elderly HNSCC are offered radical intent therapy in our clinical setup. Of these, 75% of patients complete sufficient dose of radiation therapy (≥ 60 Gray of radiation dose). Oral cavity primary and stage IV disease portend dismal outcome. EP-1154 Definitive RT and Postoperative RT of adenoid cystic carcinoma: a propensity score analysis T.H. Lee 1 , B. Jang 1 , J.H. Kim 1 , H. Wu 1 , Y.S. Seo 1 , S.H. Oh 2 , D. Kim 2 , S.K. Kwon 2 , T. Won 2 , E. Chung 2 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of ; 2 Seoul Purpose or Objective The mainstay radical treatment of adenoid cystic carcinoma in the head and neck (HNACC) is surgery. The outcome of definite radiotherapy (RT) and surgery combined with postoperative radiotherapy (PORT) has not been properly compared due to the rarity of disease and imbalances of characteristics between patients receiving either treatment. The present study aims to compare outcomes of definitive RT versus surgery + PORT for HNACC using adjustment with propensity scores (PS). Material and Methods A retrospective review of medical records was performed in patients who underwent definitive RT (n=47) or surgery + PORT (n=145) for newly diagnosed nonmetastatic HNACC between January 1981 and December 2016. A median follow-up period was 4.9 years (range, 0.34 to 27.6 years). PS was estimated using factors including age, sex, T stage, N stage, radiotherapy techniques and primary sites. Propensity score (PS) matching and inverseprobability of treatment weighting (IPTW) were used to estimate and compare survival outcomes. Results Five-year overall survival (OS), disease-free survival (DFS), locoregional control (LRC), distant metastasis-free survival (DMFS) of unmodified cohort were 75.7%, 31.4%, 66.3%, 34.2% (definitive RT) and 86.8%, 49.5%, 79.7%, 55.9% (surgery + PORT). These treatment outcomes were significantly different between two groups (p<0.05). In the PS-matched cohort, differences between the treatment outcomes were not significant. Five-year OS, DFS, LRC, DMFS of PS-matched cohort were 72.6%, 37.8%, 74.4%, 39.5% (definitive RT) and 89.3%, 48.2%, 79.0%, 52.1% (surgery + PORT). Also in the IPTW-adjusted cohort, the differences were not significant. Five-year OS, DFS, LRC, National University Hospital, Department of Otorhinolaryngology, Seoul, Korea Republic of