PurposeThe aim of this study is to detect the prognostic significance of neutrophil/lymphocyte ratio (NLR) in SCLC and to evaluate the relation with 18F-FDG PET-CT metabolic parameters (PET-CT MPs).MethodsDemographic parameters, laboratory values including NLR and other clinical variables were analyzed in 112 patients with small cell lung cancer (SCLC) and 54 of these patients had results of metabolic parameters detected with 18 FDG PET-CT [including SUVmax, SUVmean, metabolic tumor volume (MTV), whole body MTV (WBMTV), TLG (total lesion glycolysis), whole body TLG (WBTLG)] were evaluated for survival analyses.ResultsMean and median overall survival (OS) and progression-free survival (PFS) were found to be significantly longer in cases with NLR<4 compared with NLR>4 in totally. Also stage, performance status, response to first-line therapy, LDH, and lymphocyte count were found to be prognostic for OS and PFS. MTV, WBMTV and WBTLG were found to be prognostic for both OS and PFS, while SUVmax found to be significant for OS. Patients with NLR4, MTV60.1, WBMTV120 and WBTLG1000 points had lower OS and PFS. A moderate positive correlation was found between NLR and SUVmean (r: 0.36), SUVmax (r: 0.34), TLG (r: 0.39), MTV (r: 0.51), WBMTV (r: 0.40), and WBTLG (r: 0.46).ConclusionThere is relationship between PET-CT metabolic parameters and NLR in SCLC. Highest correlation was found with NLR and MTV, WBMTV, and WBTLG, and evaluation of NLR together with these parameters predicts survival times and tumor biology more clearly in SCLC.