ESTRO 2021 Abstract Book

S758

ESTRO 2021

National University College of Medicine, Department of Internal medicine, Seoul, Korea Republic of; 5 Seoul National University College of Medicine, Department of Pathology, Seoul, Korea Republic of

Purpose or Objective The role and indication of adjuvant therapy in perihilar cholangiocarcinoma remains to be elucidated. The aim of this analysis was to identify the effects of concurrent chemoradiotherapy (CCRT) and define the clearance cut-off of various margins in perihilar cholangiocarcinoma. Materials and Methods A retrospective analysis was performed on 290 patients who received definitive resection from January 2000 through December 2015. The exclusion criteria were as follows: (a) palliative resection (n=91), (b) multiple primary cancer diagnosis within 5 years (n=30), (c) adjuvant therapy at outside institution (n=19). Treatment result analysis for various end-points including overall survival (OS), disease-free survival (DFS), locoregional- recurrence free survival (LRRFS), and distant-metastasis free survival (DMFS) was performed using the Kaplan- Meier method. Results Among 150 patients of analyzed cohort, adjuvant therapy was performed in 112 (74.7%) patients: chemotherapy alone (n=6), radiotherapy (n=6), and CCRT (n=100). Number of patients with nodal and margin involvement were 45 (31.9%) and 58 (38.7%), respectively. Median follow-up duration was 24.3 months. In univariate analysis, nodal involvement (HR = 1.7, 95% CI: 1.1-2.4, p = 0.009), lymphatic invasion (HR = 1.6, 95% CI: 1.1-2.3, p = 0.011) were adverse prognostic factors for OS. In multivariate analysis, margin involvement (HR = 1.8, 95% CI: 1.1-2.8, p = 0.019) was an adverse prognostic factor for OS. CCRT was associated with better overall survival (HR = 0.5, 95% CI: 0.3-0.9, p = 0.012). On subgroup analysis for patients with nodal and/or margin involvement, survival gain was found with use of CCRT in both OS and LRRFS (p = 0.0345 and p = 0.0212, respectively). Not only margin involvement but, close resection margin was related with poor treatment results. Clearance cut-off for vascular and radial resection margin was 0.1cm and 0.2cm, respectively (p = 0.0192). Conclusion Negative surgical margins and CCRT as adjuvant treatment were statistically significant prognostic factors. Treatment result was improved with CCRT for patients with margin and/or nodal involvement. Suggested clearance for vascular and radial margin from current analysis was 0.1cm and 0.2cm, respectively. PD-0917 Twelve-year’s experience in SBRT for liver metastases, long-term results and prognostic factors. O. Hernando-Requejo 1 , C. Rubio 1 , X. Chen 1 , E. Sanchez 1 , M. Lopez 1 , R. Alonso 1 , A. Montero 1 , R. Ciervide 1 , B. Alvarez 1 , J. Valero 1 , M. Garcia-Aranda 1 , J. Garcia 2 , P. García de Acilu 2 , D. Zucca 2 , L. Alonso 2 , M.A. De la Casa 2 , J. Marti 2 , A. Prado 2 , M. Nuñez 1 , M. Izquierdo 1 , K. Rossi 1 , C. Cañadillas 1 , M.J. Salamanca 1 , F. Padilla 1 , P. Fernandez 2 1 HM Hospitales, Radiation Oncology, Madrid, Spain; 2 HM Hospitales, Medical Physics, Madrid, Spain Purpose or Objective The increase in the use of SBRT for the treatment of oligometastatic patients is due to the survival benefits demonstrated in several recent studies. One of the key challenges for the treatment of liver metastases with SBRT is the accuracy to treat this moving organ. We report our 12 years’ experience in liver metastases SBRT with intrafraction control of liver motion. Materials and Methods We retrospectively analyze the outcome of selected liver oligometastases treated with SBRT from January 2008 to May 2020. The GTV was the liver metastases, based on contrast-enhanced CT images, adding PET-CT or MRI if needed. No CTV margin was created and PTV was CTV + 5 mm margin. The total dose ranged from 36- 60Gy in 3 (48%) or 5 (52%) fractions. BED 10 was ≥100Gy in 91.6% of the lesions. IMRT with multiple conformal 6MV beams or VMAT with several arcs of 6-10 FFF-MV was used either in a Novalis or a Versa-HD LINAC (Figure 1), with daily IGRT and intrafraction control of tumor motion. Internal fiducial markers were used for IGRT with Novalis Exactrac Adaptive Gating (39.7%), and no internal fiducials were needed with intrafraction KV Conebeam CT with the Active Breathing Coordinator (53%) or Dampening (7.3%) systems used in the Versa-HD.