Immune Checkpoint Inhibitors in Advanced NSCLC: [¹⁸F]FDG PET/CT as a Troubleshooter in Treatment Response

The aim of this study was to investigate whether [¹⁸F]FDG PET/CT-derived semi-quantitative parameters can predict immunotherapy treatment response in non-small cell lung cancer (NSCLC) patients. Secondly, immune-related adverse events (irAEs) and lymphoid cell-rich organs activation were evaluated.

Twenty-eight patients who underwent [¹⁸F]FDG PET/CT scans before and at first restaging therapy with immuno-checkpoint inhibitors (ICIs) were retrospectively analyzed. PET-based semi-quantitative parameters extracted from both scans were respectively: SUV_max and SUV_peak of the target lesion, whole-body metabolic tumor volume (MTV_WB), and whole-body total lesion glycolysis (TLG_WB), as well as their interval changes (ΔSUV_maxTL, ΔSUV_peakTL, ΔMTV_WB, ΔTLG_WB). These PET-derived parameters were correlated to controlled disease (CD) assessed by RECIST 1.1. IrAEs, if present, were also described and correlated with clinical benefit (CB). SUV_max of the spleen and bone marrow at restaging scans were also correlated to CB.

The CD was achieved in 54% of patients. Out of 28 eligible patients, 13 (46%) experienced progressive disease (PD), 7 showed SD, 7 had PR, and only in one patient CR was achieved. ΔSUV_maxTL (p = 0.002) and ΔSUV_peakTL (p < 0.001) as well as ΔMTV_WB (p < 0.001) and ΔTLG_WB (p < 0.005) were significantly associated with PD vs. non-PD. IrAEs and lymphoid cell-rich organs activation did not correlate with CB.

[¹⁸F]FDG PET/CT by using interval changes of PET-derived semi-quantitative parameters could represent a reliable tool in immunotherapy treatment response evaluation in NSCLC patients.