ObjectiveTo evaluate the prognostic value of¹⁸F-fluorodeoxyglucose （¹⁸F-FDG） PET/CT metabolic parameters in small cell lung cancer （SCLC）.MethodsA retrospective analysis was conducted on the clinical and imaging data of 156 SCLC patients， who underwent¹⁸F-FDG PET/CT imaging and were diagnosed by histopathological examination at Nanjing Drum Tower Hospital， Affiliated Hospital of Nanjing University Medical School from September 2013 to February 2024. The metabolic tumor volume （MTV）， total lesion glycolysis （TLG）， linear regression slope， area under the curve of cumulative standard uptake value （SUV） volume histogram （AUC-CSH）， and coefficient of variation （CV） were calculated using LIFEx software with different SUV thresholds. Univariate and multivariate analyses were performed using Cox proportional hazards model. Patient stratification was based on the critical values determined by receiver operator characteristic （ROC） curve analysis. The survival curve was plotted using the Kaplan-Meier method and log-rank test was performed.ResultsUnivariate analysis showed that MTV_40%（HR=2.91， 95%CI： 1.55-5.47，P=0.001）， MTV_60%（HR=2.31， 95%CI： 1.29-4.17，P=0.005）， TLG_40%（HR=2.07， 95%CI： 1.19-3.60，P=0.010）， linear regression slope （HR=0.45， 95%CI： 0.26-0.79，P=0.005）， and CV_40%（HR=0.27， 95%CI： 0.08-0.84，P=0.024） were factors affecting progression-free survival （PFS） in SCLC patients. MTV_40%（HR=1.98，95%CI： 1.22-3.22，P=0.005）， MTV_60%（HR=1.80， 95%CI： 1.12-2.88，P=0.015）， MTV_80%（HR=1.71， 95%CI： 1.08-2.74，P=0.024）， TLG_40%（HR=3.68， 95%CI： 1.59-8.49，P=0.002）， linear regression slope （HR=0.49， 95%CI： 0.30-0.80，P=0.004）， and AUC-CSH_80%（HR=0.44， 95%CI： 0.23-0.84，P=0.013） were found to be factors affecting overall survival （OS） in SCLC patients. Multivariate analysis revealed that MTV_40%（HR=4.76， 95%CI： 1.11-20.50，P=0.036） was an independent factor influencing PFS， and TLG_40%（HR=3.19， 95%CI： 1.02-9.92，P=0.046） was an independent factor influencing OS in SCLC patients. ROC curve analysis identified the optimal cutoff value for MTV_40%in predicting PFS as 5.5cm³and the optimal cutoff value for TLG_40%in predicting OS as 41.5 g in SCLC patients. Survival analysis showed that patients with MTV_40%≤5.5 cm³（n=33） had a median PFS that was not reached， while patients with MTV_40%>5.5 cm³（n=123） had a median PFS of 10.3 months， with a statistically significant difference （χ²=12.09，P=0.001）. For patients with TLG_40%≤41.5 g （n=35）， the median OS was not reached， whereas for TLG_40%>41.5 g （n=121）， the median OS was 31.6 months， with a statistically significant difference （χ²=10.55，P=0.001）.ConclusionsThe¹⁸F-FDG PET/CT metabolic parameter MTV_40%is an independent factor influencing PFS， while TLG_40%is an independent factor influencing OS in SCLC patients. The above two parameters may serve as indicators for assessing the prognosis of SCLC patients.