ESTRO 2021 Abstract Book

S799

ESTRO 2021

(p=0.3). The parotid volumes were significantly larger in patients who could achieve bilateral/contralateral sparing compared to no sparing or only superficial sparing (60-63% vs 29-37%, p=0.009). the median follow-up of these patients was 18 months (Range: 6-36 months). The patients with RTOG scores (0/1) in superficial parotid sparing at 6,12 and 18 months was 55%, 49%, and 24%. Conclusion Tobacco chewers have smaller parotids and the volume of parotid correlates with the sparing achieved with IMRT in head and neck cancers. The patients whose even superficial parotids were spared had low xerostomia rates. PO-0960 Long-term outcome of IMRT-SIB and chemotherapy in nasopharyngeal carcinoma in a non- endemic area I. Linares Galiana 1 , N. Garcia Exposito 1 , M. Plana 2 , J. Brenes 2 , M. Oliva 2 , J. Nogues 3 , M. Cos 4 , L. Rodriguez 5 , J. Tornero 3 , P. Mora 6 , A. Lozano 1 1 Institut Catala d'Oncologia, Radiation Oncology, Barcelona, Spain; 2 Institut Catala d'Oncologia, Medical Oncology, Barcelona, Spain; 3 Hospital Universitario de Bellvitge, Otorhinolaryngology, Barcelona, Spain; 4 Hospital Universitario de Bellvitge, Radiology, Barcelona, Spain; 5 Hospital Universitario de Bellvitge, Nuclear Medicine, Barcelona, Spain; 6 Institut Catala d'Oncologia, Radiology, Barcelona, Spain Purpose or Objective To report the long-term clinical outcomes of nasopharyngeal carcinoma patients treated with IMRT- simultaneous integrated boost (SIB) in a non-endemic area. Materials and Methods We retrospectively reviewed the data from 104 patients with non-metastatic nasopharyngeal carcinoma who received IMRT-SIB from January 2007 to December 2017. High-risk PTV was treated with a daily dose of 2.12 Gy and a total dose of 69.96Gy. Low-risk PTV was treated with a daily dose of 1.64 Gy and a total dose of 54.12 Gy. Patients received concurrent chemotherapy during the course of the RT (CTRT) with intravenous administration of 100 mg/m 2 cisplatin every 3 weeks or 30-40 mg/m 2 weekly. The induction chemotherapy regimen was TPF (docetaxel/cisplatin/5-fluorouracil) or PF every 3 weeks for 2-3 cycles. Post-radiation adjuvant chemotherapy with PF (two-three cycles) also was used as option treatment. We analyzed the survival outcome and late toxicity outcome (scale CTCAE v5). Results 66% of all cases were men; median age was 51 years (range 15 - 83). Non-keratinizing carcinoma was the most common histological type (92%) and EBV was positive in 67/79 performed (85%). According to the AJCC 7 th Edition staging system 90.7% of cases were locally advanced disease, stage III-IVB. Only 7 patients (9.3%) were treated exclusively with RT, while the rest received chemotherapy categorized in CTRT (15.8%), induction CT + CTRT (44.6%), CTRT + adjuvant CT (5%), and induction CT + CTRT + adjuvant CT (24.8%). Response rate 8 weeks after ending radiotherapy were: complete response 69.5%, partial response 25.5%, and progressive disease 4.2%. At a median follow-up of 68 months (range 1-141), 10 patients experienced local regional failure and distant metastasis occurred in 19 patients. 5-ys Disease Free Survival was 70%, while 5-ys Overall Survival was 71.5% and did not differ by type of treatment. The most common late adverse effects were: xerostomia, dysphagia, and fibrosis. Grade 3 dental damage, hypothyroidism, and xerostomia occurred in 16.7%, 6.7% and 1.2% respectively. No case of grade IV toxicity was observed. Conclusion IMRT-SIB combined with concurrent chemotherapy or plus neoadjuvant or adyuvant chemotherapy resulted in promising rates of local regional control with acceptable rates of late side effects in patients with nasopharyngeal carcinoma. PO-0961 Role of depth of infiltration (DOI) as independent prognostic factor in pT1--T2 N0 oral tongue SCC M. Augugliaro 1 , D. Alterio 1 , M. Tagliabue 2 , P. D'urso 3 , S. Volpe 1,4 , R. Bruschini 2 , A. Farneti 3 , G. Marvaso 1,4 , I. Turturici 1 , S. Riccio 2 , B.A. Jereczek-Fossa 1,4 , G. Sanguineti 3 , M. Ansarin 2 1 IEO European Institute of Oncology, IRCCS, Division of Radiotherapy, Milan, Italy; 2 IEO European Institute of Oncology, IRCCS, Division of Otolaryngology and Head-Neck Surgery, Milan, Italy; 3 Regina Elena National Cancer Institute, IRCCS, Departments of Radiation Oncology, Rome, Italy; 4 University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy Purpose or Objective The role of dept of infiltration (DOI) as an independent prognosticator in early stage (T1-T2 N0) oral cavity tumors is controversial. Moreover, whether patients (pts) upstaged to pT3 for DOI > 10 mm need postoperative radiotherapy (PORT) in absence of other risk factors has not been established yet. The aim of the present study was to clarify both issues. Materials and Methods We performed a retrospective analysis on patients treated with surgery for early stage oral cavity tumors from 2014 to 2019 at two Institutions. After surgery, patients were staged according to the 7th ed of AJCC staging manual (disregarding DOI for staging purposes) and only pT1-2N0 tumors were selected. The role of DOI as well as other clinical/pathological features was investigated at both univariable and multivariable analyses on overall survival (OS), disease free survival (DFS), relapse free survival (RFS) and local RFS. Results Ninety-four pts (51% male, median age 63 yrs) were analyzed. Median follow-up was 24 months (range 0.5-68 months). Twenty-three patients would have been upstaged to pT3 based on DOI. Eighteen patients got PORT (all with DOI > 10 mm). The 2y overall survival (OS), disease specific survival (DSS) and locoregional control (LRC) rates were 92%, 75% and 84%, respectively. On multivariable analysis, DOI was not found to have an