Predictive value of ¹⁸F-FDG PET/CT metabolic parameters for the prognosis of small cell lung cancer

Objective  To investigate the predictive value of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT metabolic parameters for the prognosis of patients newly diagnosed with small cell lung carcinoma (SCLC) of different stages (extensive stage (ES) and limited stage (LS)).

Methods  A retrospective analysis was conducted on the clinical and imaging data of 118 patients newly diagnosed with SCLC (42 LS-SCLC and 76 ES-SCLC) at the First Affiliated Hospital of Zhengzhou University from January 2019 to December 2020. The cohort comprised 97 males and 21 females, with an age of (62.9±10.3) years. Basic clinical data (age, sex, smoking history, and weight loss); serum tumor markers (carcinoembryonic antigen (CEA), neuron specific enolase (NSE)); PET/CT metabolic parameters (whole-body metabolic tumor volume (wbMTV_40%, wbMTV_2.5) and whole-body total lesion glycolysis (wbTLG_40%, wbTLG_2.5) calculated using thresholds of 40% of maximum standardized uptake value (SUV_max) and standardized uptake value (SUV)=2.5); tumor, node, metastasis staging; Veterans Administration Lung Study Group of the United States staging; and immunohistochemistry results were collected. Overall survival (OS) was the primary endpoint. The patients were followed up until November 30, 2023. The Mann-Whitney U test was used for intergroup comparisons of measurement data, and the χ² test was used for count data. Survival rates were calculated using the Kaplan-Meier method, and survival differences were compared with the Log-rank test for univariate analysis. Variables with statistical significance in univariate analysis were included in a Cox proportional hazards regression model for multivariate analysis. Receiver operating characteristic (ROC) curve were constructed for indicators significant in multivariate analysis to evaluate predictive efficacy.

Results  Among the 76 patients with ES-SCLC, 62 died (81.6%) and 14 survived (18.4%), with a median OS of 15.0 months (95%CI: 13.1–16.9). Among the 42 patients with LS-SCLC, 30 died (71.4%) and 12 survived (28.6%), with a median OS of 22.0 months (95%CI: 15.8–28.2). The difference in median OS between the two groups was statistically significant (Z=−2.22, P=0.026). Univariate analysis showed that wbMTV_2.5 (χ²=6.01, P=0.014), wbTLG_2.5 (χ²=7.45, P=0.006), serum CEA (χ²=8.01, P=0.005), and age (χ²=4.33, P=0.037) were prognostic factors for OS in patients with ES-SCLC, whereas SUV_max (χ²=3.90, P=0.048), wbMTV_2.5 (χ²=3.86, P=0.049), and serum CEA (χ²=7.93, P=0.005) were prognostic factors for patients with LS-SCLC. Multivariate analysis indicated that serum CEA (HR=2.76, 95%CI: 1.31–5.82, P=0.008) was an independent prognostic factor for OS in patients with LS-SCLC, whereas serum CEA (HR=2.68, 95%CI: 1.49–4.81, P=0.001), wbTLG_2.5 (HR=2.32, 95%CI: 1.38–3.90, P=0.002), and wbMTV_2.5 (HR=2.17, 95%CI: 1.29–3.66, P=0.003) were independent prognostic factors for patients with ES-SCLC. ROC curve analysis showed an area under the curve (AUC) of 0.80 (95%CI: 0.68–0.93, P<0.001) for patients with ES-SCLC, with a sensitivity of 85.5% and specificity of 64.3%. By contrast, the AUC for patients with LS-SCLC was 0.83 (95%CI: 0.68–0.97, P<0.001), with a sensitivity of 86.7% and specificity of 75.0%.

Conclusions  ¹⁸F-FDG PET/CT metabolic parameters have predictive value for the prognosis of patients with SCLC. Specifically, wbMTV_2.5 and wbTLG_2.5 are independent prognostic factors for OS in patients with ES-SCLC, providing insights for clinical treatment.