Definition, Diagnosis and Treatment of Oligometastatic Oesophagogastric Cancer: A Delphi Consensus Study in Europe.

Background: Local treatment improves the outcomes for oligometastatic disease (OMD, i.e. an intermediate state between locoregional and widespread disseminated disease). However, consensus about the definition, diagnosis and treatment of oligometastatic oesopha-gogastric cancer is lacking. The aim of this study was to develop a multidisciplinary European consensus statement on the definition, diagnosis and treatment of oligometastatic oesophago-gastric cancer. Methods: In total, 65 specialists in the multidisciplinary treatment for oesophagogastric cancer from 49 expert centres across 16 European countries were requested to participate in this Del-phi study. The consensus finding process consisted of a starting meeting, 2 online Delphi ques-tionnaire rounds and an online consensus meeting. Input for Delphi questionnaires consisted of (1) a systematic review on definitions of oligometastatic oesophagogastric cancer and (2) a discussion of real-life clinical cases by multidisciplinary teams. Experts were asked to score each statement on a 5-point Likert scale. The agreement was scored to be either absent/poor (<50%), fair (50%-75%) or consensus (>75%). Results: A total of 48 experts participated in the starting meeting, both Delphi rounds, and the consensus meeting (overall response rate: 71%). OMD was considered in patients with meta-static oesophagogastric cancer limited to 1 organ with <3 metastases or 1 extra-regional lymph node station (consensus). In addition, OMD was considered in patients without pro-gression at restaging after systemic therapy (consensus). For patients with synchronous or me-tachronous OMD with a disease-free interval <2 years, systemic therapy followed by restaging to consider local treatment was considered as treatment (consensus). For metachronous OMD with a disease-free interval >2 years, either upfront local treatment or systemic treatment fol-lowed by restaging was considered as treatment (fair agreement). Conclusion: The OMEC project has resulted in a multidisciplinary European consensus state -ment for the definition, diagnosis and treatment of oligometastatic oesophagogastric adeno-carcinoma and squamous cell cancer. This can be used to standardise inclusion criteria for future clinical trials. 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).