Total metabolic tumor volume on 18F-fluorodeoxyglucose-positron emission tomography ([18F]-FDG-PET) scan: A potential prognostic factor in extensive-stage small cell lung cancer.

Abstract

8574 Background: Small-cell lung cancer (SCLC) is a highly aggressive neuroendocrine lung cancer, accounting for 10-15% of all lung cancers, commonly classified in limited stage (LS-SCLC) and extensive stage (ES-SCLC). Despite the introduction of chemoimmunotherapy as new standard first-line therapy for ES-SCLC, the benefit of addition of the programmed-death ligand 1 (PD-L1) inhibitors is limited to a subset of patients, suggesting the importance to identify predictive biomarkers of response. [18F]FDG-PET/CT is commonly used for the staging and therapeutic planning of SCLC patients. Metabolic parameters derived from [18F]FDG-PET could predict patient outcomes by measuring the extension of metabolically active tumor (metabolic tumor volume [MTV]) or its metabolic heterogeneity (total lesion glycolysis [TLG]). Methods: We retrospectively collected patients with pathologically confirmed diagnosis of SCLC, who had undergone an [18F]FDG PET/CT scan within 30 days from the start of first-line treatment for ES-SCLC. Patients with LS-SCLC at diagnosis were included if presenting relapse at pre-treatment scans performed at least 90 days from the end of treatment with radical intent. We calculated metabolic parameters, MTV and TLG, by summing each single lesion’s MTV and TLD respectively. The primary endpoint of the study was overall survival (OS), defined as the time from [18F]FDG PET/CT scan acquisition to death from any cause. Results: A total of 86 SCLC patients ES-SCLC were included. Patients with hyponatremia, hypoalbuminemia and elevated LDH levels were associated with greater number of lesions, greater total MTV, and higher total TLG at [18F]FDG-PET/CT/CT scan. At a median follow-up of 20.9 months, the median OS was 11.1 months. Median survival was longer among patients with Na + ≥135 mEq/L, with normal albumin levels and in those with normal LDH levels and without bone metastases. Patients with low total MTV had longer OS compared with those with high total MTV (11.9 months vs 4.8 months, respectively). High total MTV was independently associated with the risk of death (p < 0.001) but not with the risk of progression. Conclusions: Our preliminary data showed that total MTV could provide prognostic information in patients with ES-SCLC, suggesting a potential role as stratification factor in immunotherapy-based clinical trials.