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ESTRO 37

Conclusion Hypofractionated RT achieved high locoregional disease control rate and cancer-specific survival rate. Fraction size of 2.25Gy provided good local control regardless of the use of SIB dose with 2.5Gy. IMRT may be possible to reduce toxicity compared with 3D CRT. EP-1141 Treatment outcomes of olfactory neuroblastoma: two institutional study J.H. Chung 1 , I.A. Kim 2 , J.S. Kim 2 , H.G. Wu 1 , K.Y. Eom 2 1 Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of 2 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam-si-, Korea Republic of Purpose or Objective We aimed to analyze oncologic outcomes and assess the impact of clinic-pathologic factors on survival outcomes. Material and Methods In this retrospective study, 77 histologically confirmed olfactory neuroblastoma (ONB) patients were accrued from Seoul National University Hospital and Seoul National University Bundang Hospital between Jan 1999 and Dec 2016. Patients treated by two dimensional radiotherapy (RT) were excluded. Median follow-up time was 59.1 months (range, 2.6-238.7). Results The 5-year overall survival (OS), disease-free survival (DFS), loco-regional recurrence-free survival (LRRFS), and distant metastasis-free survival (DMFS) were 80.4%, 62.2%, 74.7%, and 79.5%, respectively. Local recurrence occurred in 15 patients (19.5%): 9 of 61 (14.8%) received RT and 6/16 (37.5%) did not. Regional recurrence occurred in 12 patients (15.6%) in whom 9 of 12 have not undergone any kind of neck treatment. In univariate analysis, RT was a prognostic factor for favorable local recurrence-free survival (LRFS) (p=0.007). 2Gy-per- fraction equivalent dose (EQD2) higher than 55Gy was associated with favorable local and loco-regional control rate (p=0.010, p=0.010, respectively). In clinical N0 patients, Kadish stage C/D (p=0.015) and clinical tumor size greater than 5.5cm (p=0.010) were related to higher nodal recurrence. Conclusion RT delivery and EQD2 higher than 55Gy is recommended to improve local control rate in ONB patients. For clinical N0 patients with Kadish stage C/D and/or large tumor size, elective neck treatment would be helpful to reduce regional failure. EP-1142 Application of de-intensified radiotherapy in elderly head and neck cancer patients J. Choi 1 , S.H. Choi 1 , K.C. Keum 1 , C.G. Lee 1 1 Yonsei University, Radiation Oncology, SEOUL, Korea Republic of Purpose or Objective Elderly patients may experience increased toxicity or less benefit from standard therapy. In this study, we evaluated the outcome of de-intensified radiotherapy (RT) for locoregionally confined head and neck cancer management in elderly patients. Material and Methods A retrospective review was conducted of head and neck cancer referrals to RT between August 2007 and December 2016 at our institution. A total of 261 elderly patients over 65 years of age, who were available for analysis on pattern of failure, outcome, and toxicity, were classified into two groups: standard (n=129) and non-standard treatment (n=132) for RT. Non-standard treatment group comprised those treated with de- intensified RT, including patients with radiation alone (n=38), radiation dose reduction (n=72), and/or field reduction (n=30) due to old age.

Results The median age at the treatment was 72 years (range 65- 94). The most common primary site was larynx (n=69) followed by oropharynx (n=46), oral cavity (n=46), and hypopharynx (n=43). Fifty-eight patients were in stage I-II and 199 patients were in stage III-IV. Among 261 patients, 114 patients were treated with definitive RT, 133 patients with postoperative RT, and 14 patients with salvage RT. While the patients in the standard treatment group included more favorable primary sites and stage I or II disease (p<0.001) compared with non-standard treatment group, there was no significant difference in overall survival (OS, p=0.08) and recurrence-free survival (RFS, p=0.381) between two groups. After a median follow-up period of 18.6 months (range 1.5–119.1), the 2- year OS and local control rate were 92.3% and 73.9% for standard group vs. 84.2% and 69.2% for non-standard group, respectively. Overall, 67 patients (32/129 vs. 35/132) experienced treatment failures, which were classified as local in 16 patients, regional in 25 patients, and distant in 31 patients. No differences were found between standard and non-standard treatment group in grade 3 or higher xerostomia (2.3% vs. 1.5%), skin reaction (12.4% vs. 18.2%), and mucositis (38% vs. 33.3%), respectively. Conclusion Our results show that age-concerned RT for elderly patients is tolerable and the therapeutic effect is comparable to the outcome from reported standard treatment group. Therefore, de-intensified RT in head and neck cancers provides good control rates for elderly patients who appear not to be suitable for standard of care and probable of cure. EP-1143 Prognostic significance of combined lymphocyte counts and body mass index in head and neck cancer Y.Y. Wu 1 , N.M. Tsang 1 1 Chang Gung Memorial Hospital, Radiation oncology, Taoyuan, Taiwan Purpose or Objective We aimed to investigate the prognostic significance of combined pretreatment lymphocyte counts (LCs) and body mass index (BMI) in patients with head and neck cancer (HNC) treated with radiation therapy (RT). Material and Methods Nine hundred and twelve patients with HNC who were treated with RT were retrospectively reviewed. Survival was analyzed by stratifying the patients according to pretreatment LCs and BMI. Results Patients with low pretreatment LCs and BMI were characterized by a more advanced T stage, fewer nasopharyngeal subsites, less smoking and drinking, and fewer comorbidities. Patients with low pretreatment LCs and BMI had a significantly poorer overall and distant metastasis-free survival than those with high pretreatment LCs and BMI. No significant differences were observed in terms of local or regional recurrence- free survival. Conclusion Combined pretreatment LCs and BMI may be more effective at predicting overall and distant metastasis-free survival in patients with HNC treated with RT . EP-1144 PTPN14 as a potential marker of local recurrence after PORT in patients with SCC of the oral cavity. J. Szelachowska 1 , D. Zielecka-Debska 2 , K. Lichon 2 , A. Pomiecko-Olszowy 3 , A. Maciejczyk 4 , R. Matkowski 2 , A. Chalon 5 1 Lower Silesian Oncology Center, Gynaecological Oncology Clinic, Wroclaw, Poland 2 Lower Silesian Oncology Center, Department of