ESTRO 37 Abstract book

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ESTRO 37

planning system data, retrospectively. Receiver operating characteristic (ROC) curves were generated to identify cut-off values for pEBV-DNA and GTVt. The Kaplan-Meier method was used for survival analysis. Results Nine (20.9%) out o f 43 patients have undetectable pEBV- DNA at initial diagnosis. The median copy number of pEBV-DNA before treatment was 397 copies/mL (0 – 124.800 cp/ml). According to ROC curve analysis, pEBV- DNA cut-off value was 6.335 cp/ml for overall survival (OS) (AUC: 0.942, sensitivity:100%, specificity: 87.5%). 3- year OS rates in patients with pEBV-DNA < 6.330 cp/ml vs > 6.330 cp/ml were 100% and 51.4% (p<0.0001), and the disease-free survival (DFS) rates were 100% and 14.3% (p<0.0001), respectively. The 3-year OS rates in patients with positive and negative pretreatment pEBV-DNA were 91.2% and 100% (p=0.35), and DFS rates were 75.6% and 100% (p =0.6), respectively. The median gross tumor volume of the primary NPC (GTVp), the lymph node lesions (GTVln), and the total GTV (GTVt) before treatment were 25.2, 8.3, and 41.9 cm3, respectively. According to ROC curve analysis, GTVt cut-off value was 30.1 cm 3 for OS (AUC: 0.700, sensitivity:87.5%, specificity: 43.3%). The initial pEBV-DNA levels were significantly correlated with the GTVln and the GTVt (p<0.002, p<0.0001), but not with GTVp (p>0.05).The 3- year OS rates in patients with GTVt < 30.1 cm 3 vs > 30.1 cm 3 were 100% and 83.4% (p = 0.06), and DFS rates were 95.8% and 70.5% (p =0.09), respectively. Conclusion Our results indicate that high pretreatment pEBV-DNA levels in patients with NPC are associated with the degree of lymph node metastasis, tumor burden, and poor prognosis. Though there was a trend of decreased OS and DFS in patients with large GTVt volumes, it did not reach statistical significance. EP-1174 Outcomes in patients with cervical paragangliomas treated with intensity-modulated radiotherapy. A. Rochand 1 , F. Tankere 2 , J. Jacob 1 , P. Herman 3 , P. Maingon 1 , L. Feuvret 1 1 Hospital Pitié-Salpétrière, Radiation Therapy, Paris, France 2 Hospital Pitié-Salpétrière, Head and Neck Surgery, Paris, France 3 Hospital Lariboisière, Head and Neck Surgery, Paris, France Purpose or Objective To retrospectively assess the outcomes of intensity- modulated radiotherapy (IMRT) in patients with head and Between 2011 and 2016, 21 patients (9 male, 12 female) with 24 head and neck paragangliomas were treated by IMRT in 25 fractions at median dose of 45Gy [range 45 – 68]. One case was malignant. Anatomical sites were tympano-jugular (n=15), carotid (n=4), vagal (n= 4), and oropharyngeal (n=1). The mean gross target volume and planning target volume were 26.33 cm³ [range 5.8–72.7] and 92.45 cm³ [range 30.6–162.8], respectively. Median age was 61 years [range 31–77]. Two patients had SDHD mutations, 3 SDHB mutations and 14 patients were not genetically tested . Fourteen patients had IMRT as primary treatment, 4 patients had IMRT for relapse after initial surgery and 3 patients had complementary IMRT after surgery. Median follow-up of 21.9 months [range 2.76– 60.8] Results Local tumor control was 100% (Complete Response=1, Partial Response=3, Stable Disease=20). During the treatment, excepted a grade 2 facial paralysis reversible with corticotherapy, no upper Grade 2 acute side effect was reported. The most frequent side effect reported neck paragangliomas. Material and Methods

Figure 1. Composition of the MTV in percentage. Red line: volume of recurrence. Blue line: volume of response to the treatment. Table 1. P-values of Wilcoxon signed-rank test, for histogram and texture features.

Conclusion Although the SUVmean of GTVfailure was significantly higher than the SUVmean of GTVr, recurrence origin was not only located within regions of high FDG uptake . However, some texture features as Entropy, Inverse Difference Moment and Cluster Shade seems to be correlate with recurrence origin , what pave the way for prediction based on FDG uptake features in order to tailor CRT treatment of locally advanced HNC. EP-1173 Impact of plasma Epstein-Barr virus-DNA and gross tumor volume on prognosis of nasopharyngeal cancer T. Zoto Mustafayev 1 , B. Sahin 1 , B. Atalar 1 , E. Ozyar 1 1 Acibadem University, Radiation Oncology, istanbul, Turkey Purpose or Objective In this retrospective study, we aimed to investigate the association of plasma Epstein-Barr virus DNA (pEBV-DNA) levels with the gross tumor volume and their impact on prognosis in patients with nasopharyngeal cancer (NPC). Material and Methods A total of 68 patients with newly diagnosed NPC patients were treated between March 2009 to June 2017. pEBV- DNA was analysed using fluorescence quantitative polymerase chain reaction (PCR) amplification in 43 (63%) out of 68 patients. There were 5, 18, 36, and 9 cases of stage I, II, III, and IVa-b disease, respectively, according to the 8th edition of American Joint Committee on Cancer staging system. All patients were staged with PET-CT and/or MRI scan beside the conventional blood tests. All patients were treated either with IMRT or VMAT techniques. The gross primary and involved lymph node volume was calculated in 68 patients using treatment