Abstract Book

S772

ESTRO 37

Conclusion Neoadjuvant CCRT provides improved PFS and OS in patients with early stage esophageal cancer. For patients with tumors located in the middle or lower thoracic esophagus, inclusion of high mediastinal lymph node areas within the radiation field for neoadjuvant chemoradiotherapy may be needed. EP-1420 Stereotactic body radiation therapy for resectable but medically inoperable pancreatic cancer X. Zhu 1 , L. Fuqi 1 , S. Dongchen 1 , J. Xiaoping 1 , C. Yangsen 1 , S. Yuxin 1 , C. Fei 1 , Q. Shuiwang 1 , F. Fang 1 , J. Zhen 1 , Z. Huojun 1 1 Changhai Hospital, Radiation Oncology, Shanghai, China Purpose or Objective Although surgical resection has been confirmed as the only strategy for cure, especially for resectable pancreatic cancer, only 15-20% of the patients were amenable to this curative-intent treatment at the initial diagnose. Moreover, there was no consensus or clinical trials about optimal multimodality treatment for patients with resectable but medically inoperable pancreatic cancer. As a result, radiotherapy and chemotherapy may be the alternatives if patients are not candidates for surgery. Given the shortcomings of conventional radiotherapy, stereotactic body radiation therapy (SBRT) has become a promising option due to its precise treatment delivery with sharp dose fall-off within adjacent organs at risk, acceptable toxicity, on-line image verifications and shorter courses. Therefore, in this study, we sought to evaluate the efficacy and safety of SBRT and identify clinical factors associated with survival in a large cohort of patients with resectable but medically inoperable pancreatic cancer. Material and Methods From 2012 to 2016, patients with radiographically resectable, biopsy-proven pancreatic cancer were included. Cox proportional hazards regression was used to identify factors predictive of survival. Propensity score matching analysis was employed to assess the efficacy of SBRT combined with different chemotherapy regimens. Results A total of 100 patients were included in the study. The median prescription dose and BED 10 were 37Gy (range: 30-46.8Gy) and 61.92Gy (range: 48-88.32Gy) in 5-8 fractions, respectively. The systemic treatment regimens included gemcitabine based and S-1 based chemotherapy regimens. The median overall survival (OS) and progression free survival (PFS) were 17.5 months and 13.7 months, respectively. Post-SBRT chemotherapy, CA19-9 response and BED 10 ≥60Gy correlated with OS and PFS. Patients with more predictive factors had a better prognosis. Longer OS, not PFS, was found in patients with S-1 based post-SBRT chemotherapy (24.3 months vs. 21.6 months, P=0.023). Furthermore, given that the overall duration of 6-cycle S-1 based chemotherapy was much longer than that of 6-cycle gemcitabine based chemotherapy, another 30 patients receiving S-1 based chemotherapy with the similar duration were included for analysis. After the propensity score matching analysis, the median OS of S-1 based and gemcitabine based chemotherapy group was 24.4 months and 21.6 months (P=0.022), respectively. The median PFS of the two groups was 20.0 months and 16.9 months (P=0.037). No Grade 3 or more radiation-induced toxicity was found. A higher incidence of hematologic and gastrointestinal toxicity was found in gemcitabine based chemotherapy and S-1 based chemotherapy, respectively. Conclusion SBRT was safe and effective in resectable pancreatic cancer. Higher doses may be beneficial for survival. Combined with chemotherapy, SBRT could be an alternative for patients with resectable pancreatic cancer but not eligible for surgical resection.

multidisciplinary board evaluation. Prescription dose was 45Gy in 6 fractions. Primary end-point was freedom from local progression (FFLP). Secondary end-points were overall survival (OS), progression-free survival (PFS), and toxicity. Local control (LC) was defined according to RECIST v1.1 criteria. Acute and late toxicity was scored according to the NCI Common Terminology Criteria for Adverse Events (CTCAE) v3.0. Results Between January 2011 and December 2016, 100 patients (44 male-56 female) with LAPC were treated with SBRT at Humanitas cancer Center. Median age was 71 years (range 41-88 years). 57 patients (57%) received CT before SBRT, for a median time of 5 months (range 3 - 10 months). In 44 patients (77%) gemcitabine-based CT was administered ( 4 gemcitabine alone, 21 GEMOX, 9 PEX-G, 10 gemcitabine-nab paclitaxel), whereas 13 patients (33%) received FOLFIRINOX. Median follow-up was 86 months (range 2-88 months). FFLP was 82% and 76% at 1 and 2 years, respectively. At univariate (p<0.03) and multivariate analysis (p<0.001), lesion size was significant for LC. Median PFS was 7 months (95% CI 4.76-8.23). Median OS was 13 months (95% CI 8.76-13.21). CT administered before SBRT (p< 0.005) and FFLP (p<0.002) were significantly correlated with OS. Grade 3 gastrointestinal toxicity was detected in 2% of patients. Conclusion SBRT is an effective and safe local therapy for selected patients with LAPC. Our results suggest that the stereotactic treatment may be a promising therapeutic option in the multi-modality treatment of these patients. EP-1419 Outcomes according to radiation fields of neoadjuvant chemoradiotherapy for esophageal cancer N. Choi 1 , W. Jeon 1 , H.C. Kang 1 , H.J. Kim 1 , S. Kim 2 1 Seoul National University Hospital- Seoul National University College of Medicine, Radiation Oncology, Seoul, Korea Republic of 2 Seoul Metropolitan Government Boramae Medical Center- Seoul National University College of Medicine, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective The purpose of this study is to analyze the treatment outcomes and patterns of failure after neoadjuvant concurrent chemoradiotherapy (CCRT) and surgery for esophageal cancer. Material and Methods Medical records of 62 esophageal squamous cell carcinoma patients treated with neoadjuvant CCRT from 2005 to 2014 were retrospectively reviewed. The median follow-up duration was 12.8 months (range 1.3-141.7). Results Of the 62 patients who fully completed neoadjuvant CCRT, 77.4% underwent subsequent surgery. The most common cause rendering patients to be unsuitable for surgery was disease progression. Failure occurred in 25 (52.1%) patients, of which distant failure was most common. Locoregional failure was observed in 13 (27.1%) patients, of which 8 and 5 patients had in-field and out- of-field recurrences, respectively. The 2-year progression-free survival (PFS) rate was 48.6% and 2-year overall survival (OS) rate was 53.8%. On multivariate analysis, clinical stage III-IV before surgery (HR 6.8, 95% CI 1.6-29.0, p=0.010 for PFS and HR 3.1, 95% CI 1.2-7.9, p=0.021 for OS) and pathologic up-staging after surgery (HR 17.8, 95% CI 4.1-78.1, p<0.001 for PFS and HR 12.0, 95% CI 4.3-33.1, p<0.001 for OS) were independently significant risk factors for poor PFS and OS. Supraclavicular and mediastinal nodal recurrence was observed more commonly in middle and lower thoracic esophageal cancer, with a significantly higher proportion occurring outside the radiation field (p<0.001).