ESTRO 38 Abstract book

S414 ESTRO 38

responders in esophageal cancer. Moreover, 18 F-FDG PET/CT and DW-MRI are of complementary value in the assessment of histopathological response. PO-0799 Treatment outcomes of nodal positive unresectable thoracic esophageal carcinoma T. Huang 1 , S. Li 2 , Y. Chen 2 , H. Lu 3 , C. Lo 3 , F. Fang 1 , S. Chou 1 , Y. Wang 1 1 Kaohsiung Chang Gung Memorial Hospital and Chang Gung University School of Medicine, Proton and radiation therapy center, Kaohsiung, Taiwan ; 2 Kaohsiung Chang Gung Memorial Hospital and Chang Gung University School of Medicine, Department of Hematology- Oncology, Kaohsiung, Taiwan ; 3 Kaohsiung Chang Gung Memorial Hospital and Chang Gung University School of Medicine, Department of Thoracic & Cardiovascular Surgery, Kaohsiung, Taiwan Purpose or Objective The prognosis of unresectable (T4b) thoracic esophageal cancer (EC) is extremely poor and the optimal treatment strategy remains controversial. The present study investigated the treatment outcomes and prognostic factors of nodal positive (N+) T4b thoracic EC patients treated by curative intent concurrent chemoradiotherapy (CCRT). Material and Methods A retrospective review of 1120 EC patients treated at our institution between 2009 and 2017 was conducted. One hundred and twenty T4b N+ thoracic EC patients without distant metastasis who underwent curative CCRT were identified for the following study. Among these patients, 84 patients were treated by definitive CCRT only (dCCRT) while salvage esophagectomy was performed in 36 patients (CCRT+S). All clinical factors were put into analysis. Survival analysis was calculated using Kaplan- Meier method with log-rank test, and prognostic factors were examined by Cox proportional hazards model. Results The median survival for the entire group of 120 patients was 15.5 months.The 1-year, 3-year, and 5-year overall survival (OS) was 60.2%, 29.5%, and 22.5%, respectively. Multivariable analysis revealed that CCRT+S (p = 0.014), age <= 65 (p = 0.001), Pre-CCRT body mass index (BMI) > 22 (p = 0.001), and clinical N1 (cN1) disease (p = 0.005 ) were significant independent prognostic factors. Tumor location (upper/middle/lower) and different invasion structures (great vessels, airway, or both) had no significant influence on OS.

corresponding concordance measurements were calculated to evaluate the complementary value of 18 F- FDG PET/CT and DW-MRI.

Results A total of 69 patients with 203 18 F-FDG PET/CT and 199 DW-MRI scans were eligible for analysis. A pCR was found in 26.1% (18/69). Relative changes in 18 F-FDG PET/CT parameters after nCRT (ΔSUV mean,post [median, IQR] -63% (- 68%, -49%) for pCR versus -42% [-58%, -16%] for non-pCR, p = 0.018 and ΔTLG post [median, IQR] -86% [-93%, -81%] for pCR versus -65% [-88%, -32%] for non-pCR, p = 0.036), as well as changes in DW-MRI parameters during nCRT (ΔADC during [median, IQR] 28% [15%, 39%] for pCR versus 11% [3.7%, 17%] for non-pCR, p = 0.006) were significantly different between pathologic complete responders and non-responders in esophageal cancer (Table 1). A c- statistic of 0.74 for ΔSUV mean,post alone, of 0.77 for ΔADC during alone and of 0.81 for the combination of ΔADC during with ΔSUV mean,post was obtained in classifying patients as pCR and non-pCR.

Conclusion This prospective multicenter study demonstrates that changes in 18 F-FDG PET/CT parameters after nCRT (ΔSUV mean,post and ΔTLG post ) and early treatment-induced changes on DW-MRI during nCRT (ΔADC during ) discriminate between pathologic complete responders from non-