ESTRO 37 Abstract book

S632

ESTRO 37

Material and Methods We performed a retrospective analysis of 69 patients who were pathologically diagnosed primary OCSCC between Jul 2006 and Dec 2016. The included subsites were oral tongue (30 patients), gum (17), floor of mouth (11), retromolar trigone (6), buccal mucosa (4), and hard palate (1). Lip cancer was excluded. Thirty patients received definitive CCRT and 39 patients received PORT. All patients were treated with intensity-modulated radiation therapy. Patients receiving CTx were treated with cisplatin-based regimen and 11 patients (28.2%) received CCRT in PORT arm. The primary endpoint was overall survival (OS) and secondary endpoints were locoregional control (LRC), distant metastasis-free survival (DMFS), and toxicity. Results Median follow-up period was 21 months (range, 2-91). Median radiation dose for the definitive CCRT arm was 72.6 Gy (range, 70-77), and the postoperative arm was 66 Gy (range, 55-72.6). The overall stage between two treatment arms was not statistically different (p=0.082), definitive CCRT arm showed trend to higher overall stage. During follow-up, 29 patients (42.0%) experienced treatment failure, locoregional failure in 28 patients (40.6%) and distant failure in 8 patients (11.6%). The 2- year cumulative OS, LRC, and DMFS in CCRT arm were 66.3 %, 75.8%, and 89.0%, respectively. The 2-year cumulative OS, LRC, and DMFS in PORT arm were 73.3%, 67.3%, and 86.1%, respectively. No statistical differences were observed in OS (p=0.345), LRC (p=0.845), and DMFS (p=0.865). In multivariate analyses, N0-1 stage and treatment end within 8 weeks were significant prognostic factors for OS (p<0.05), and treatment end within 8 weeks was only significant prognostic factor for LRC (p=0.033). In subgroup analyses of CCRT arm, T1-3 stage and N0-1 stage were significant prognostic factors (p<0.05) for OS and treatment end within 8 weeks showed marginal significance for both OS (p=0.070) and LRC (p=0.057). In PORT arm, only N0-1 stage was a statistically significant prognostic factor (p=0.007). One patient experienced grade 4 sepsis in definitive CCRT arm but recovered with management. There was no difference in rates of acute and late complication over grade 2 between two treatment arms.

group receiving FDG-PET/CT guided dose painting by contours (DPBC). Material and Methods Our conventional re-irradiation regimen is hyperfractio- nated radiotherapy 1.5 Gy twice daily over 4 weeks, giving a total dose of 60 Gy. For DPBC, we defined two prescription volumes, PV33 and PV66, corresponding to 33% and 66 % of the highest FDG uptake in the tumor, respectively. The CTV prescription dose was 60 Gy, PV33; 65 Gy and PV66; 70 Gy and Dmax 75 Gy. Nine patients who had followed our conventional re-irradiation protocol were compared to five patients who had received dose painting. Using the National Cancer Institute-Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 3.0, the difference in toxicity score at baseline and after treatment was calculated for each patient for all of the 26 separate parameters (including xerostomia and dysphagia). Furthermore, the summed value for all parameters was also calculated. From this, the score differences were organized in two groups for each parameter according to treatment. Mann–Whitney U test was performed on each selection. Results Dose painting resulted in an increase in D2cc (highest dose to 2cc volume) of typically 10 Gy compared to conventional therapy when both treatment plans were summed with the primary treatment series. There was overall little change in the toxicity score in both treatment groups. Measured bodyweight had the greatest change, with a median decrease of 3% for all 14 patients, but no statistically significant difference was found between the groups. Considering all toxicity scores using the NCI-CTCAE, we found no significant difference in the change in summed score from baseline as compared to 1) the end of treatment and 2) the first follow-up 2 months after treatment between the nine patients treated according to the standard protocol and the five patients who received treatment with dose painting. Conclusion Our three-contour dose painting approach gave a maximal dose increase to the patient of about 10 Gy. Although the follow-up period is limited, these results support the hypothesis that dose painting does not contribute to added morbidity compared to a conventional approach. EP-1121 Treatment of oral cavity cancer: concurrent chemoradiotherapy vs surgery followed by radiotherapy J. Park 1 , J.E. Lee 1 , K.H. Seol 2 , J.H. Sohn 3 , D. Ahn 3 1 Kyungpook National University School of Medicine, Radiation Oncology, Daegu, Korea Republic of 2 Catholic University of Daegu School of Medicine, Radiation Oncology, Daegu, Korea Republic of 3 Kyungpook National University School of Medicine, Otorhinolaryngology–Head and Neck Surgery, Daegu, Korea Republic of Purpose or Objective The optimal treatment for locally advanced oral cavity squamous cell carcinoma (OCSCC) is surgical resection followed by postoperative radiotherapy (RT) with/ without chemotherapy (CTx). However, definitive concurrent chemoradiotherapy (CCRT) is an alternative treatment option for patients not amenable to surgery or unwanted to undergo surgery such as facial deformity, swallowing difficulties, and phonation impairment. Therefore, we performed this study to evaluate clinical outcomes of definitive CCRT compared to surgery followed by postoperative RT with/without CTx (PORT).