Abstract
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Objectives: The aim of this study was to determine the impact of metabolic response with 18F-FDG PET/CT in patients with non-small cell lung carcinoma (NSCLC) treated with Immune Checkpoint Inhibitors (ICI).
Methods: The trial was registered at http://www.clinicaltrials.gov (NCT03563482). In this prospective study we analyzed data from 25 patients (16 male, 9 female, mean age 68) with NSCLC treated with ICI from April 2017 to December 2018. All patients were investigated with 18F-FDG PET/CT and contract enhanced CT at baseline and 8 weeks after the start of ICI. In all cases, we determined metabolic response based on EORTC criteria and morphological response based on iRECIST. As metabolic parameters, we utilized also metabolic tumor volume (MTV), total lesion glycolysis (TLG), as well as percentage change in SUVmax (ΔSUVmax), MTV (ΔMTV) and TLG (ΔTLG). With a median follow-up of 7.5 months, response criteria we mutually compared and correlated to progression-free survival (PFS). All variables were statistically analyzed by means of the Statistical Package for Social Sciences (SPSS).
Results: Based on metabolic response, after 8 weeks of ICI we determined 8 PMR (32%), 11 SMD (44%) and 6 PMD (24%) patients. Median values for the other metabolic parameters resulted ΔSUVmax=8.21%, ΔMTV=67.7% and ΔTLG=37.6%. On counterpart, according to morphology, there were 5 PR (20%), 11 SD (44%) and 9 PD (36%) patients. On log rank test, EORTC response classified as PMR vs SMD/PMD resulted significantly correlated to PFS (p=0.048). Univariate analysis with Cox proportional hazards determined a statistically significant association to PFS also for ΔSUVmax (p=0.009), ΔMTV (p=0.03) and ΔTLG (p=0.013). When analyzed separately in patients resulting in PR or SD according to morphology, metabolic response with EORTC criteria significantly differentiated patients having a longer PFS (p=0.023; HR 0.229).
Conclusions: In NSCLC undergoing ICI, metabolic response with 18F-FDG PET/CT allows for the prediction of patients with longer PFS. The added value of EORTC criteria is confirmed for patients presenting with a PR or SD according to iRECIST. The Italian Association for Research on Cancer (AIRC - Associazione Italiana per la Ricerca sul Cancro) is acknowledged for the support on this research.