ESTRO 2021 Abstract Book

S1001

ESTRO 2021

Conclusion Our results suggest that sex, length of oesophageal disease and concurrent chemotherapy protocol are the most influential variables in predicting pathological response.

PO-1206 SBRT in pancreatic cancer - a single institution experience A. Secerov Ermenc 1 , N. Dobnikar 1 , I. Oblak 1 , A. Jeromen Peressutti 1 1 Institute of Oncology, Division of Radiotherapy, Ljubljana, Slovenia

Purpose or Objective Despite continued advancements in treatment modalities, the survival rate of patients with pancreatic cancer (PC) remains poor. Stereotactic body radiotherapy (SBRT) is a novel treatment with promising results in local control and minimal toxicity. Materials and Methods We retrospectively analyzed the data from patients with PC who were treated with SBRT at our institution from October 2018 to January 2021. We included patients with locally advanced, borderline resectable and recurrent PC. They received SBRT with the dose of 25-30 Gy to the tumor and 35-50Gy to the vessel encasement in 5 fractions. Restaging scans were performed approximately every 3 months with toxicity assessment. Results Twenty-one patients were available for analysis, ten patients had locally advanced PC, ten patients had recurrent and one had borderline PC. Median age was 66 years, thirteen patients were men and eight were women. The median dose to the vessel encasement was 35.5 Gy delivered in 5 fractions. Twelve patients (57%) received also systemic therapy. The median overall survival (OS) and 1-year OS were 13.2 months and 61%, respectively. No patient underwent surgery after evaluation. 1-year progression free survival and 1-year local control were 41% and 65%, respectively. 1-year local control for the patients with locally advanced PC was 75%. We did not observe acute grade > 2 toxicity. Eight patients reported pain in the upper abdomen because of PC prior SBRT, after treatment we observed a significant relief. Conclusion SBRT provides high local control with a good toxic profile, moreover it can improve symptom control and aid pain relief in patients with advanced stages of pancreatic cancer. PO-1207 Stereotactic radiotherapy and MR-guided adaptive techniques for locally advanced pancreatic cancer T. Ermongkonchai 1 , R. Khor 1 , V. Muralidharan 2 , N. Tebbutt 3 , K. Lim 4 , N. Kutaiba 4 , S.P. Ng 1 1 Olivia Newton-John Cancer Wellness & Research Centre, Department of Radiation Oncology, Melbourne, Australia; 2 Austin Health, Department of Surgery, Melbourne, Australia; 3 Olivia Newton-John Cancer Wellness & Research Centre, Department of Medical Oncology, Melbourne, Australia; 4 Austin Health, Department of Radiology, Melbourne, Australia Purpose or Objective Pancreatic cancer is one of the leading causes of cancer deaths. Surgical resection is the only curative option but is rarely feasible due to late presentation. Stereotactic body radiotherapy (SBRT) is a novel radiation technique developed to reduce radiation-related toxicity whilst delivering high ablative radiation doses to the tumour. However, the poor soft-tissue visualisation of computed tomography (CT) imaging incorporated in SBRT prevents dose escalation. This led to the emergence of magnetic resonance (MR)-guided techniques to circumvent these limitations. Here, we aim to review and report on the latest data on SBRT and the role of MR-guided techniques to enhance multimodal management of pancreatic cancer. Materials and Methods A systematic search on PubMed and Ovid (Medline) was done to collate the latest records on radiotherapy techniques for pancreatic cancer. The literature includes SBRT and/or MR-guided adaptive radiotherapy on unresectable pancreatic neoplasms. Studies were excluded if they were on metastatic disease, resectable tumours, or chemoradiotherapy as adjuvant treatment after surgery. Results Out of 1219 total records retrieved, 13 studies were included in this review. Four of these studies demonstrate SBRT’s superior clinical efficacy and toxicity profiles compared to conventional radiotherapy techniques. SBRT achieved median overall survival (OS) rates between 6-23 months, with grade 3 toxicity rates of 10% or less. Interestingly, a small proportion of unresectable patients were converted to surgical resectability after SBRT treatment. Seven studies demonstrated conversion rates of 5-18%. The study that achieved 18% resectability involved patients treated with high-dose regimens (42-45 Gy in 6 fractions) compared to standard regimens (20-40 Gy in 3-6 fractions). This suggests that the key determinant in conversion is dose escalation. Two