ESTRO 2023 - Abstract Book

S1089

Digital Posters

ESTRO 2023

PO-1358 Stereotactic Body Radiotherapy (SBRT) for unresectable liver metastases. Clinical outcomes.

L.A. Perez-Romasanta 1 , B. De la Plaza Villanueva 1 , C. Nicolas Boluda 1 , M.B. Cuesta Picon 1 , J. Henandez Rodriguez 2 , S. Garcia Repiso 2 , A. Rodriguez Gonzalez 1 , A. Matias Perez 1 1 Hospital Universitario de Salamanca, Radiation Oncology, Salamanca, Spain; 2 Hospital Universitario de Salamanca, Radiation Physics, Salamanca, Spain Purpose or Objective Stereotactic body radiotherapy (SBRT) is an alternative treatment option for liver metastases in patients unsuitable for surgery and/or interventional procedures. We investigated factors associated with clinical outcomes for liver metastases treated with SBRT from a single center. Materials and Methods Patients with liver metastases treated with SBRT were identified in hospital patient registry. Patient, tumor and treatment characteristics associated with treatment outcomes were assessed. Dose fractionations were normalized to BED10. Overall survival (OS), progression free survival (PFS) and local failure free survival (LFFS) were evaluated using Kaplan Meier analysis and log-rank test. Results The study included 24 patients, 77% males, with 48 liver metastases. Median age was 70 years (55–89 years). Colorectal adenocarcinoma (CRC) was the primary cancer for 34 metastatic lesions (70.8%) and synchronous/metachronous distribution was 52.1%/47.9%. Most patients had a previous history of metastatic disease, 77.1% oligo- and 18.8% polymetastatic. Most lesions (75%) had received prior treatment. Mean PTV volume was 65.4 cm3 (2.7–333.3 cm3) and mean SBRT dose was 46.8 Gy (40–54 Gy) delivered in a median of 5 fractions. At a median follow-up of 24 months (5-65 m.) the median PFS and OS were 6.7m. and 38m. respectively. Median OS for patients with CRC and with no-CRC were 38.6m. vs. 32.3m (p=0.209), and for patients with synchronous/metachronous metastases were 38.5m vs. 38.7 (p=0.833). Smaller PTV volumes (< 65 cm3) or higher BED did not correlate with improved OS (p=0.128 and p=0.522). Location of primary tumor (CRC vs. non CRC) correlated with SLP (7.1m vs 3.8m; p=0.044). Local failure correlated with synchronous/metachronous lesion status (Median LFFS 25.1m vs. 32.7m; p=0.022). There was no difference in LFFS based on PTV volume or BED. Conclusion In this single institution series of patients with liver metastasis treated with SBRT, satisfactory outcomes were observed. Location of the primary tumor and metachronous development of metastases correlated with better disease control. 1 Klinikum rechts der Isar, Technical University of Munich (TUM), Department of Radiation Oncology, Munich, Germany; 2 Klinikum rechts der Isar, Technical University of Munich (TUM), Medical Clinic and Polyclinic II, Munich, Germany; 3 Klinikum rechts der Isar, Technical University of Munich (TUM), Department of Surgery, Munich, Germany; 4 Institute of Radiation Medicine (IRM), Department of Radiation Sciences (DRS), Helmholtz Zentrum München, Neuherberg, Germany; 5 Deutsches Konsortium für Translationale Krebsforschung (DKTK), Partner Site Munich, Munich, Germany; 6 Klinikum rechts der Isar, Technical University of Munich (TUM), Department of Radiation Oncology , Munich, Germany Purpose or Objective Pancreatic ductal adenocarcinoma (PDAC) remains one of the most aggressive and lethal solid tumors with an estimated 5 year overall survival rate of less than 10%. The role of radiotherapy (RT) within a multidisciplinary therapeutic approach is controversially discussed due to a high resistance to standard treatment modalities. This study aims to analyze the clinical outcome of patients with locally advanced PDAC who underwent induction chemotherapy followed by RT. Materials and Methods The present study is a retrospective single-center analysis including patients with non-metastatic, locally advanced histologically confirmed PDAC. A total of 25 patients treated in our department of radiation oncology from 2014 to 2022 were included. All patients received induction chemotherapy with median 7 (range 2-12) cycles of FOLFIRINOX (77.8%), or median 4 (range 4-5) cycles of gemcitabine/paclitaxel (22.2%). RT was either performed as conventionally fractionated radiochemotherapy (RCHT, 66.7%) or stereotactic body radiation (SBRT, 33.3%). Toxicity was evaluated according to the CTCAE version 4, and survival was analyzed by Kaplan-Meier method and Log-Rank-Test (Mantel-Cox). Results The median age at diagnosis was 60 (range 48 - 77) years. Most tumors were located in the pancreatic head (64%), followed by the pancreatic body (28%), and pancreatic tail (8%). The median prescribed total doses were 38.6 Gy (25.0 - 40.0 Gy) in 5 fractions for patients who underwent SBRT, and 55.6 Gy (45.0 - 58.8 Gy) in 25 - 31 fractions for patients who underwent RCHT, respectively. Concurrent gemcitabine- (16.7%) or capecitabine-based (83.3%) chemotherapy regimens were applied in the RCHT group. Patients tolerated both radiation regimes without any acute or late severe toxicity (grade ≥ 3). A subsequent laparotomy was performed in 63% of all patients (17/27): a surgical resectability was feasible in 65% (11/17), whereas a R0-resection was achieved in 45% (5/11). Median survival from the time of diagnosis was 22 months (6-54 months). Distant metastases free survival (DMFS) was 19 PO-1359 Implementation of modern radiotherapy in a multimodal approach of locally advanced pancreatic cancer S. Dobiasch 1,4,5 , M. Waltenberger 1 , M. Reichert 2 , H. Friess 3 , R.M. Schmid 2 , S.E. Combs 1,4,5 , S. Münch 6