Combining (18)F‐FDG PET/CT and Serum Lactate Dehydrogenase for Prognostic Evaluation of Small Cell Lung Cancer

Objective: To investigate the value of using (18)F-FDG PET/CT in combination with serum lactate dehydrogenase (LDH) for prognostic evaluation of newly diagnosed small cell lung cancer (SCLC). Methods: We reviewed 118 patients with pathologically proven SCLC who underwent (18)F-FDG PET/CT imaging evaluation in our hospital. Among these patients, 64 patients had extensive disease (ED) and 54 patients had limited disease (LD). The maximum standardized uptake value (SUV(max)) of primary tumor was measured. A Cox proportional hazards model was used to evaluate age, sex, performance status, serum LDH, tumor stage and SUV(max) on the prediction of overall survival (OS) and median survival time (MST) of patients. Subgroup analysis was performed based on the SUV(max) in combination with serum LDH. Results: According to the Receiver Operating Characteristic (ROC) curve, the optimal cut-off value of SUV(max) was 10.95. The AUC was 0.535 (95% CI: 0.407–0.663). The patients were divided into four groups according to the SUV(max) (higher or lower than 10.95) and LDH (higher or lower than 245 U/L). The univariate and multivariate analyses showed that curative thoracic radiotherapy, Prophylactic Cranial Irradiation (PCI) and the combination of primary tumor SUV(max) ≤ 10.95 and LDH ≤ 245 U/L were prognostic factors of OS in patients with all patients (p < 0.05). Smoking status, PCI, the combination of primary tumor SUV(max) ≤ 10.95 and LDH ≤ 245 U/L were prognostic factors of OS in patients with LD (p < 0.05). N stage and PCI were significant predictors in both of univariate and multivariate analysis of OS for ED SCLC (p < 0.05). Among all patients, 27 had low SUV(max) and normal LDH, and their MST was 36 months (95% CI: 12.98–59.02). Ninety-one patients had high SUV(max) and/or high LDH, and their MST was 20 months (95% CI: 15.47–24.53). The difference between these two groups was significant (p = 0.045). In patients with LD, 16 patients had low SUV(max) and normal LDH, and their MST was 72 months (95% CI: 26.00–118.0). Thirty-eight patients had high SUV(max) and/or high LDH, and their MST was 27 months (95% CI: 20.80–33.21). The difference between these two groups was significant (p = 0.012). In patients with ED SCLC, 10 patients had low SUV(max) and normal LDH, with an MST of 18 months (95% CI: 13.69–22.32. Fifty-four patients had high SUV(max) and/or high LDH, and their MST was 12 months (95% CI: 10.61–13.39). The difference of MST between these two groups was not statistically significant (p = 0.686). Conclusion: (18)F-FDG PET/CT in combination with serum LDH were prognostic factors of overall survival in patients with SCLC. The prognosis of patients with LD SCLC who had low SUV(max) of primary tumor and normal LDH was better than those with high SUV(max) and/or high LDH.