A new proposal of simplified classification of non-small cell lung cancer oligometastases for easy applicability through systematic literature analysis and meta-analysis validation.

INTRODUCTION: Oligometastasis (OM) exhibits wide range of prognosis, which necessitates appropriate classification for optimal therapeutic decision-making. Complementing the ESTRO-EORTC classification which lacked prognostic differentiation and was rather complex, we propose a new and simpler classification based on systematic literature analysis and meta-analysis validation. METHOD: The databases were searched up to April 2024. Inclusion criteria were (1) ≥ 10 Non-small cell lung cancer OM patients, (2) local ablative treatment (LAT) versus control (systemic/supportive treatment), (3) reporting progression free survival (PFS) or overall survival (OS), respectively. A simpler classification was proposed through systematic reviews evaluating outcomes based on OM characteristics. According to this new classification, the LAT benefit and pooled 2-year OS and 1-year PFS percentiles were validated through meta-analysis. RESULTS: In overall meta-analysis, LAT was correlated with enhanced 1-year PFS (odds ratio (OR):3.487, p < 0.001) and 2-year OS (OR:2.984, p < 0.001), respectively. According to simplified classification, LAT benefit of 1-year PFS was differentiated with ORs of 5.631 (p < 0.001), 3.484 (p < 0.001), and 1.702 (p = 0.067) for Synchronous (Syn), OPS (Oligopersistence), and OPR (Oligoprogression/recurrence) subgroups, respectively. Inter-subgroup comparisons showed significant differences as well. For 2-year OS, ORs of LAT benefit were 3.366 (p < 0.001), 3.355 (p < 0.001), and 1.821 (p = 0.127) in Syn, OPS, and OPR subgroups, respectively; LAT benefit was significant in Syn and OPS, but not significant in OPR. In pooled percentile comparison, 1-year pooled PFS was significantly lower in the OPR group than others, both in the LAT and control arms. CONCLUSION: Based on a systematic literature analysis and meta-analysis validation, we developed a simpler three-step OM classification: Syn, OPS, and OPR. We would propose this new classification that is simpler and more applicable to clinical decisions than the currently available classification.