ESTRO 2021 Abstract Book

S542

ESTRO 2021

SP-0680 A. Tree

Abstract not available

Symposium: Radiotherapy in oesophageal cancer

SP-0682 To operate or not after neoadjuvant chemoradiation M. Nilsson 1 1 Karolinska Institutet, CLINTEC, Division of Surgery, Stockholm, Sweden

Abstract Text Currently there are a number of evidence and guideline-based options available for curative intent treatment of oesophageal cancer. Based on trials published so far surgery is still a mandatory part of a multimodality approach for fit adenocarcinoma (AC) patients, as complete pathological response to chemoradiotherapy only occurs in 20-25%, and clinical response evaluation is still inaccurate. For AC perioperative chemotherapy (FLOT regimen) together with surgery is another alternative. For squamous cell carcinoma (SCC) there are two main curative intent treatment options. The most well-documented treatment strategy is neoadjuvant chemoradiotherapy (nCRT) using the CROSS regimen with paclitaxel-carboplatin and 41.4 Gy, followed by planned surgery, with an impressive overall five-year survival of around 60%. Another guideline recommended curative intent option for SCC is definitive chemoradiotherapy (dCRT), with several alternative regimens, followed by surveillance and salvage oesophagectomy only when needed for local tumour control. So far no adequately powered randomized trial has been published comparing these two alternative treatment approaches for esophageal SCC. Significant efforts have been made to document and improve clinical response evaluation after chemoradiotherapy. In preSANO, a prospective multicenter diagnostic cohort study, response evaluation tools including endoscopy with conventional and bite-on-bite biopsies, PET-CT and EUS with fine needle aspiration biopsies were evaluated after nCRT and compared to pathological assessment of the surgical specimens. The best accuracy was achieved in combining endoscopic bite-on-bite biopsies with EUS and fine needle aspiration biopsies, with a negative predictive value for residual tumour tissue of 45%, meaning that clinical complete responders still had residual tumour in 55% of cases. This indicates that in clinical practice clinical response evaluation after chemoradiotherapy, using the tools currently available, is still too inaccurate to alone be used to select patients for non-surgical management after nCRT. This is especially true for AC. The Dutch SANO trial, further evaluating this management strategy, recently completed accrual, and the similar Dutch- Chinese SINO trial is ongoing. A more pragmatic approach to clinical response evaluation, currently used in clinical practice after dCRT, is using the tools above over a period of time within a surveillance programme, acknowledging that radiological progression from one follow-up investigation to a subsequent one, may at times be a sufficient indication for salvage oesophagectomy even in the absence of pathological evidence of residual or recurrent tumour. This is important given the low negative predictive value of endoscopic biopsies, in order to avoid progression beyond salvage operability. This approach is used in the ongoing randomized international NEEDS trial on operable SCC patients, in which CROSS type nCRT followed by planned oeosphagectomy is compared to dCRT followed by surveillance and salvage oesophagectomy only when needed for local tumour control. SP-0684 How to deal with respiratory and cardiac movement? L. Hoffmann 1 , P.R. Poulsen 2 , M. Nordsmark 2 , A. Hegener 3 , M.L. Ehmsen 4 , T.B. Nyeng 1 , C.M. Lutz 1 , T. Ravkilde 1 , J. Bertholet 5 , I. Kruhlikava 6 , M. Dufour 7 , H. Mortensen 8 , M. Alber 9 , D.S. Møller 1 1 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark; 2 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 3 Aarhus University, Department of Clinical Oncology, Aarhus, Denmark; 4 Aarhus University Hospital, Danish Centre for Particle Therapy,, Aarhus, Denmark; 5 Bern University Hospital, Department of Radiooncology, Bern, Switzerland; 6 Aarhus University Hospital, Department of Surgery, Aarhus, Denmark; 7 University of Turin, Department of Physics, Turin, Italy; 8 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; 9 Heidelberg University Hospital, Germany, Department of Radiation Oncology, Heidelberg, Germany Abstract Text Purpose/Objective: Detailed knowledge of target motion is important for improved accuracy and decreased toxicity in esophageal cancer radiotherapy. Strategies to mitigate cardiac and respiratory motion are discussed. Differences in the effect of motion on proton and photon therapy quality will be highlighted. Material and methods: Uncertainties during treatment can be divided into intra-fractional (respiratory and cardiac motion, and patient or target positional shifts) and inter-fractional (anatomical changes, changes in respiratory motion, setup errors) categories. Using projection images from setup CBCT scans and kV- flouroscopy recorded during treatment delivery, the 3D trajectories of implanted fiducials in the target region can be obtained by the method of kilovoltage intrafraction monitoring (KIM). The extracted motion includes both intra- and inter-fractional shifts as well as the respiratory and cardiac motion. Anatomical changes and SP-0683 The role of proton therapy in the treatment of esophageal cancer S. Lin USA Abstract not available