ESTRO 2025 - Abstract Book

S1847

Clinical – Upper GI

ESTRO 2025

University College of Medicine, Seoul, Korea, Republic of. 8 Department of Surgery, Yonsei University College of Medicine, Seoul, Korea, Republic of. 9 Esophageal Surgery Division, national Cancer Center Hospital, Tokyo, Japan. 10 Division of Gastric Surgery, Shizuoka Cancer Center, Nagaizumi, Japan. 11 Division of Gastric Surgery, National Cancer Center Hospital East, Kashiwa, Japan. 12 Department of Thoracic and Cardiovascular Surgery, University of Texas MD Anderson, Houston, USA. 13 Department of Surgical Oncology, University of Texas MD Anderson, Houston, USA. 14 Department of Gastrointestinal Medical Oncology, University of Texas MD Anderson, Houston, USA. 15 Gastric and Mixed Tumor Service, Memorial Sloan Kettering Cancer Center (MSK), New York, USA. 16 University of Pittsburgh Medical Center, Pittsburgh Medical Center, Pittsburgh, USA. 17 Division of Thoracic Surgery, McGill University Health Centre, Montreal, Canada. 18 Universidade de São Paulo, Department of Gastroenterology, São Paulo, Brazil. 19 Esophageal Unit, Hospital Universitario Fundación Falvoro, Buenos Aires, Argentina. 20 Clínica AlemanaSurgery Department, Hospital Militar de Santiago, Santiago, Chile. 21 Department of Medical Oncology, Amsterdam UMC, location University of Amsterdam, Amsterdam, Netherlands. 22 Cancer Center Amsterdam, Cancer Treatment and Quality of Life, Amsterdam, Netherlands. 23 Radiation Oncology, Amsterdam UMC, Location VU,c, Amsterdam, Netherlands Purpose/Objective: Approximately 25% of esophagogastric cancer patients present with oligometastatic disease (OMD). A recent Chinese phase-II randomized trial demonstrated a survival benefit of adding local treatment for OMD in patients with esophageal squamous cell cancer (SCC), whilst conflicting results from the RENAISSANCE AIO-FLOT5 trial in OMD from gastric or junctional adenocarcinoma were recently presented. The differences in outcome may in part be explained by a lack of consensus in the definition of OMD criteria. This project aims to investigate intercontinental differences in esophagogastric OMD definition, diagnosis and treatment. Material/Methods: This study is derived from the OMEC-2 project, in which the multidisciplinary team meetings (MDTs) of 49 European experts centers were asked for their opinion on 15 real-life cases. These cases were now presented to 20 key opinion leaders from 9 countries in North and South America, Asia, and Oceania. Agreement among MDTs was scored as no agreement (<50%), fair agreement (50-75%) or consensus (≥75%).

Results:

In November-December 2023, 15 of 20 invited MDTs (i.e., 75% response rate) completed the 15 case discussions. Consensus was found regarding the following statements: OMD was considered in cases involving 1-2 metastatic lesions in the lung(s), soft tissue, adrenal gland or retroperitoneal lymph node(s). OMD was also considered in cases with human epidermal growth factor receptor (HER2) positive adenocarcinoma (AC). In case of progression in the number of lesions at restaging, the disease state was no longer considered oligometastatic. 18 F-FDG PET/CT was considered most appropriate for restaging lesion(s) in the liver, lung(s), retroperitoneal and cervical lymph node(s), adrenal gland(s), and soft tissue (consensus). Systemic therapy to consider local treatment was considered in patients with OMD from HER2-positive adenocarcinoma (consensus). No other treatment strategies for OMD reached consensus, but systemic therapy to precede consideration of local treatment for oligometastases reached fair agreement most frequently. Among two cases presenting with cervical lymph node metastases, 53% and 47% of MDTs classified these as locoregional rather than distant metastases. Asian MDTs (n=6) demonstrated a higher likelihood to categorize these same metastases as locoregional, compared to non-Asian MDTs (n=9), with rates of 67% vs. 44% for the first case and 67% vs. 33% for the second case.