EORTC Lung Cancer Group survey on the definition of NSCLC synchronous oligometastatic disease

Background: Synchronous oligometastatic disease (sOM) has been described as a distinct disease entity; however, there is no consensus on OM definition (OM-d) in non–small-cell lung cancer (NSCLC). A consensus group was formed aiming to agree on a common OM-d that could be used in future clinical trials. A European survey was circulated to generate questions and input for the consensus group meeting. Methods: A European Organisation for Research and Treatment of Cancer Lung Cancer Group (LCG)/sOM-d consensus group survey was distributed to LCG, sOM-d consensus group, and several European thoracic oncology societies’ members. Results: 444 responses were analysed (radiation oncologist: 55% [n = 242], pulmonologist: 15% [n = 66], medical oncologist: 14% [n = 64]). 361 physicians (81%) aimed to cure sOM NSCLC patients and 82% (n = 362) included the possibility of radical intent treatment in their sOM-d. The maximum number of metastases considered in sOM-d varied: 12% replied 1 metastasis, 42% ≤ 3, and 17% ≥ 5 metastases. 79% (n = 353) stated that number of organs involved was important for sOM-d, and most (80%, n = 355) considered that only ≤3 involved organs (excluding primary) should be included. 317 (72%) included mediastinal lymph node involvement in the sOM-d and 22% (n = 70/317) counted mediastinal lymph node as a metastatic site. Most physicians completed sOM staging with brain magnetic resonance imaging (91%, n = 403) and positron emission tomography/computed tomography (98%, n = 437). Pathology proof of metastatic disease was a requirement to define sOM for 315 (71%) physicians. The preferred primary outcome for sOM clinical trials was overall survival (73%, n = 325). Conclusion: Although consensual answers were obtained, several issues remain unresolved and will require further research to agree on a sOM-d.