Defining oligometastatic non-small cell lung cancer: A simulated multidisciplinary expert opinion

Synchronous oligometastatic non-small cell lung cancer (NSCLC) definition varies from 1 metastasis in 1 organ (tumour-node-metastasis 8 [TNM8]), 1-3 metastases (European Society for Medical Oncology [ESMO]), ≤3 metastases (including mediastinal nodes [MLN]) after systemic treatment to 3-5 metastases in ongoing trials. A single definition is however needed to design/compare trials. To assess oligometastatic NSCLC definitions used by clinical experts in daily practice and its evolution, we redistributed a 2012 case-based survey (Dooms, the World Congress of Lung Cancer 2013).

In December 2017, 10 real-life multidisciplinary team (MDT) discussed patients (good condition, no significant comorbidities, ¹⁸F-fluorodeoxyglucose positron emission tomography/brain magnetic resonance imaging staged, all < 5 metastases, 9/10 ≤ 3 metastases, oncogene-addicted or wild-type) were distributed to 33 international NSCLC experts involved in the European Organisation for Research and Treatment of Cancer oligometastatic NSCLC consensus group, questioning is this oligometastatic disease and if oligometastatic, which treatment proposal. The answers provided in 2017 were compared with the 2012 answers; real-life treatment and survival of the patients was added.

Twenty-six of 33 experts (24 centres) replied: 8 medical oncologists, 7 pulmonologists, 7 radiation oncologists, 4 thoracic surgeons. Sixty-two percent of respondents discussed the cases with their MDT. One case had 100% oligometastatic consensus, and 3 cases had >90% consensus; the number of treatment proposals varied between 3 and 8. Radical treatment was more often offered in case of single metastasis or N0. Compared with 2012, there was a trend towards a more conservative oligometastatic definition and chemotherapy was more frequently included in the treatment proposal.

Oligometastatic NSCLC definition was conservative. The number of organs, MLN status and radical treatment possibility seem to be components of daily practice oligometastatic definition.