ESTRO 37 Abstract book

ESTRO 37

S395

Material and Methods Seven hundred and sixty-eight patients who were treated for hepatocellular carcinoma at our institution between 2012 and 2016 were retrospectively reviewed. Among these, 663 patients who underwent RFA of 731 tumors and 105 patients who underwent SBRT of 114 tumors were included. The most frequently used dose- fractionation schedule in SBRT was a total of 60 Gy in 4 fractions and a total of 52 Gy in 4 fractions. Radiological responses were assessed using the modified response evaluation criteria in solid tumors (mRECIST). To minimize the effects of potential confounders and selection bias, propensity score matching analysis (PSM) was performed. Finally, 95 tumors were selected from each treatment arm. Freedom from local progression (the primary endpoint, FFLP) was compared before and after adjustment with PSM. Results At baseline, SBRT-treated tumors were more advanced, larger (median, 2.4 vs. 1.6 cm), and more frequently located in the subphrenic region than RFA-treated tumors (50.0% vs. 31.1%, P < 0.001). The median follow-up was 21.5 (range, 0.7–64.2) months. Before PSM, the 1- and 2- year FFLP rates were 85.7% and 76.3% for the SBRT group and 82.6% and 70.4% for the RFA groups, respectively ( P = 0.265). After PSM, the 1- and 2-year FFLP rates were 83.7% and 74.9% for the SBRT group and 76.1% and 64.9% for the RFA group, respectively ( P = 0.243). The local control rates were not significantly different between the two groups before or after PSM. The Cox proportional hazards model revealed the treatment modality as an independent predictor of local recurrence favoring SBRT in the entire cohort (HR: 1.96, 95.0% CI: 1.21–3.17; P = 0.006) and in the PSM model (HR: 1.73, 95.0% CI: 0.98– 3.05; P = 0.060). Tumor location (subphrenic region) and tumor size (>2.0 cm) were independent predictors in the RFA group but not in the SBRT group. Overall toxicity rate did not differ between two groups. Conclusion Both SBRT and RFA can achieve excellent local control for localized HCC. SBRT appears to be an effective alternative treatment for hepatocellular carcinoma when RFA is not feasible due to tumor location or size. PO-0766 Feasibility of radiotherapy for hepatocellular carcinoma with Child-Pugh class B (KROG 16-05) W.S. Yoon 1 , S.H. Bae 2 , H.C. Park 3 , S.M. Yoon 4 , J. Seong 5 , J.W. Kim 6 , T.H. Kim 7 , T.K. Nam 8 , Y.M. Choi 9 , S.Y. Lee 10 , H.S. Jang 11 , J.H. Kim 12 , D.S. Lee 13 1 Korea University Ansan Hospital, Radiation Oncology Department, Ansan- Danwon-gu, Korea Republic of 2 Soonchunhyang University College of Medicine, Radiation Oncology, Bucheon, Korea Republic of 3 Samsung Medical Center- Sungkyunkwan University School of Medicine, Radiation Oncology, Seoul, Korea Republic of 4 Asan Liver Center- University of Ulsan College of Medicine, Radiation Oncology, Seoul, Korea Republic of 5 Severance Hospital- Yonsei University College of Medicine, Radiation Oncology, Seoul, Korea Republic of 6 Gangnam Severance Hospital- Yonsei University College of Medicine, Radiation Oncology, Seoul, Korea Republic of 7 Center for Liver Cancer- Research Institute and Hospital- National Cancer Center, Radiation Oncology, Goyang, Korea Republic of 8 Chonnam National University Medical School, Radiation Oncology, Gwangju, Korea Republic of 9 Dong-A University College of Medicine, Radiation Oncology, Busan, Korea Republic of 10 Chonbuk National University Hospital, Radiation Oncology, Jeonju, Korea Republic of 11 Seoul St. Mary’s Hospital- The Catholic University of Korea-, Radiation Oncology, Seoul, Korea Republic of

regimens of different modalities as well as the optimal treatment sequence are still a matter of debate. Therefore, the aim of the study evaluate the factors associated with different treatment sequences and strategies for LAPC and their impacts on overall survival (OS) and progression free survival (PFS). Material and Methods Patients with radiographically LAPC, biopsy-proven pancreatic cancer receiving stereotactic body radiation therapy (SBRT) and chemotherapy were included. Factors associated with treatment sequences were analyzed with Chi-square test and its contingency coefficient. Cox proportional hazards regression was used to identify factors predictive of survival. Propensity score matching analysis was employed to further assess different treatment strategies and chemotherapy regimens. Results Four hundred and nineteen patients were included with the median prescription dose and BED 10 were 36Gy and 61.92Gy in 5-8 fractions, respectively. The median overall survival (OS) and progression free survival (PFS) were 13.2 months and 8.2 months, respectively. Pre- treatment ECOG correlated with pre-SBRT chemotherapy while tumor stage, lymph node invasion and toxicity after SBRT associated with post-SBRT chemotherapy. Longer OS was found in patients with pre-SBRT chemotherapy alone (12.2 months), post-SBRT chemotherapy alone (13.6 months) and pre- and post-SBRT chemotherapy (13.3 months) compared with those without chemotherapy (11.2 months) due to systemic disease or poor performance status (P<0.001), while only post-SBRT chemotherapy alone (8.6 months) and pre- and post-SBRT chemotherapy (8.1 months) increased PFS. After adjustment, patients with post-SBRT chemotherapy alone had a marginal OS and PFS benefit compared with pre- and post-SBRT chemotherapy (OS: 14.7 months vs. 13.1 months, P<0.001; PFS: 8.8 months vs. 8.1 months, P=0.053). Furthermore, adjusted survival benefit was found in patients with S-1 based regimen compared with gemcitabine based regimen used in post-SBRT chemotherapy alone (OS: 14.7 months vs. 13.4 months, P=0.02; PFS: 8.8 months vs. 8.5 months, P=0.029). To preclude potential impacts of chemotherapy courses on prognosis, further analysis on similar durations of these two regimens also confirmed the survival benefits produced S-1 based chemotherapy. Conclusion Post-SBRT and pre- and post-SBRT chemotherapy for LAPC patients could improve OS and PFS. Pre-treatment performance status, tumor stage, lymph node involvement and toxicity after SBRT influenced treatment sequences. PO-0765 Efficacy of stereotactic body radiation therapy over radiofrequency ablation for HCC N. Kim 1 , H.J. Kim 1 , J.Y. Won 2 , D.Y. Kim 3 , K.H. Han 3 , J. Seong 1 1 Yonsei University College of Medicine, Radiation Oncology, SEOUL, Korea Republic of 2 Yonsei University College of Medicine, Radiology, SEOUL, Korea Republic of 3 Yonsei University College of Medicine, Internal Medicine, SEOUL, Korea Republic of Purpose or Objective Several non-surgical, locoregional curative treatments are available for localized hepatocellular carcinoma (HCC), including stereotactic body radiation therapy (SBRT), radiofrequency ablation (RFA). Until now, little evidence has been available for determining the efficacy of SBRT in comparison to RFA. We evaluated the efficacy of SBRT and RFA for hepatocellular carcinoma.