Abstract Book

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ESTRO 37

To identify pathological risk factors for disease-free survival (DFS) in patients with p16-negative and p16- positive oropharyngeal cancer Material and Methods We analyzed 94 patients with oropharyngeal squamous cell carcinoma who had received radical surgery and adjuvant radiotherapy with or without concurrent chemotherapy at kangdong sacred heart hospital during 2004 Sep to 2017 Mar. Test for p16 status was done in 53 patients using PCR and human papilloma virus DNA microchip. Among of them, 23 patients were proven their positivity for p16. DFS was estimated using Kaplan Meier method and difference of survivals according to individual risk factors were analyzed by Log-rank test. Results Median duration of follow-up was 40 months. Five year DFS was 73.2% for overall patients, 66.5% for p16- negative patients, and 81.6% for p16-positive patients, respectively. Depth of invasion >2cm ( P =0.032), pathological extranodal extension ( P =0.014, Fig.1), 4 or more lymph node involvement ( P <0.001), greatest dimension of lymph node >3cm ( P =0.006), contralateral and/or bilateral lymph node involvement ( P =0.005) and level IV lymph node involvement ( P <0.001) were significantly associated with worse DFS for p16-negative patients. For p16-positive subgroup, contralateral and/or bilateral lymph node involvement ( P =0.001) were significantly associated with worse DFS, however, pathological extranodal extension ( P =0.490, Fig.2), 4 or more lymph node involvement ( P =0.382) and greatest dimension of lymph node >3cm ( P =1.000) were not.

significantly relevant for p16-positive patients. Therefore, identical indication for adjuvant radiotherapy should not be applied to both p16-positive and p16- negative patients. Deintensified adjuvant strategy for p16-positive oropharyngeal squamous cell carcinoma seems to be needed. EP-1135 Effects of different treatment and EBV viral load in stage III nasopharyngeal carcinoma patients J.C. Lin 1 , W. Wen-Yi 2 , L. Yi-Chun 1 1 Taichung Veterans General Hospital, Department of Radiation Oncology, Taichung, Taiwan 2 Hung Kuang University, Department of Nursing, Taichung, Taiwan Purpose or Objective To investigate the prognostic impacts of different treatment modality and pretreatment plasma EBV DNA levels in patients with stage III nasopharyngeal carcinoma (NPC). Material and Methods This retrospective study collected 356 previously untreated, pathologically-proven NPC patients with stage III disease. The initial definitive treatment consisted of concurrent chemoradiotherapy (CCRT, n=145) or induction chemotherapy plus radiotherapy (IndCT-RT, n=211). Eighty-four of 356 (23.6%) patients also received post-RT adjuvant chemotherapy. The pre- treatment EBV DNA level was measured by the real-time quantitative polymerase chain reaction. We arbitrarily divided patients into a high (> 1000 copies/mL, n=106) or low (< 1000 copies/mL, n=250) viral load subgroup. Subsequent relapse rates and various survival curves were compared between different treatment modality and EBV viral load. Results Baseline characteristics between CCRT and IndCT-RT were no significant differences except for a higher percentage of N2 disease in the IndCT-RT subgroup (92.4% vs. 80.0%, P=0.0005). Both treatment modality resulted in similar relapse rates (20.0% vs. 17.5%, P=0.5566). The overall survival (OS, P=0.1980), progression-free survival (PFS, P=0.5339), distant metastasis failure-free survival (DMFFS, P=0.8870), and locoregional failure-free survival (LRFFS, P=0.3516) between CCRT and IndCT-RT revealed no statistically significant difference. However, patients with a high viral load experienced a higher relapse rate (33.0% vs. 12.4%, P<0.0001) and worse OS (5-year rate, 79.0% vs. 92.8%, P<0.0001), PFS (73.7% vs. 88.4%, P<0.0001), DMFFS (80.2% vs. 95.0%, P<0.0001), and LRFFS (85.6% vs. 92.6%, P=0.0045) than those with a low viral load. Conclusion IndCT-RT can reach the same treatment outcome as the current standard CCRT for stage III NPC patients. The pretreatment EBV DNA level identified a subgroup of patients, who presented with a higher viral load and suffered from significantly worse survivals. Strengthen treatment intensity for these subgroup patients deserves to study in future trials. EP-1136 Interaction of chemotherapy with radiation and surgery in nasal cavity and nasal sinus cancer T. Zhao 1 , Z. Yin 2 , G. Li 1 1 Beijing Hospital, radiation department, Beijing, China 2 Tianjin Medical University Cancer Institute & Hospital, Radiation department, Tianjin, China Purpose or Objective To evaluate the necessity of chemotherapy in nasal cavity and nasal sinus carcinoma, and to clarify the influence of surgery or radiotherapy on the outcome of chemotherapy.

Conclusion p16-positive oropharyngeal cancer revealed to be a distinctive disease entity. Especially, extranodal extension had strong prognostic value for p16-negative oropharyngeal cancer, on the other hand, was not