⁶⁸Ga-NK224 PET/CT Reveals Intra- and Intertumoral Heterogeneity of PD-L1 in Non-Small Cell Lung Cancer

Background Programmed death ligand 1 (PD-L1) expression assessed via immunohistochemical analysis of single-site biopsies is standard for guiding immunotherapy in non-small cell lung cancer (NSCLC). However, this approach fails to capture intra- and intertumoral heterogeneity. Purpose To investigate whether gallium 68 (⁶⁸Ga) NK224 PET/CT enables whole-body assessment of PD-L1 expression and heterogeneity in NSCLC and whether lesion-specific treatment response is associated with PET-defined PD-L1 uptake. Materials and Methods In this prospective study conducted from December 2023 to July 2025, participants with newly diagnosed or recurrent or metastatic NSCLC underwent ⁶⁸Ga-NK224 PET/CT and PD-L1 immunohistochemical analysis. Tumor uptake of ⁶⁸Ga-NK224 was quantified using maximum standardized uptake value (SUV_max) from biopsy-plane regions of interest (ROIs) and whole-lesion ROIs. PD-L1 tumor proportion score (TPS) was the reference standard. Intratumoral heterogeneity was assessed using the normalized range of SUV_max, and intertumoral heterogeneity was evaluated using the SUV_max coefficient of variation across lesions. Results This study included 48 participants (median age, 68 years [IQR, 59-75 years]; 31 men). Across 52 lesions, ⁶⁸Ga-NK224 uptake differed among PD-L1 TPS categories (P < .001), and biopsy-plane SUV_max correlated strongly with TPS (Spearman ρ = 0.80; P < .001). Receiver operating characteristic analysis identified an optimal SUV_max cutoff of 5.6 for discriminating tumors with high PD-L1 expression. Among 12 participants classified as PD-L1 negative via immunohistochemical analysis, five had one or more lesions with SUV_max above the cutoff (15 of 68 lesions). Intratumoral heterogeneity was substantially higher when assessed using whole-lesion ROIs (median normalized range, 1.0) versus biopsy-plane ROIs (median normalized range, 0.4) (P < .001). Intertumoral heterogeneity within individual participants was pronounced (median SUV_max coefficient of variation, 23.6% [IQR, 17.9%-36.7%]). In participants receiving immunotherapy (24 lesions), lesions with partial or complete response (shrinkage ≥30%; median shrinkage, 47.5%) showed greater ⁶⁸Ga-NK224 uptake than lesions with progressive or stable disease (shrinkage <30%; median shrinkage, 7.4%) (median SUV_max, 5.9 vs 1.9; P = .01). Conclusion ⁶⁸Ga-NK224 PET/CT enabled whole-body assessment of PD-L1 heterogeneity in NSCLC and revealed lesion-level heterogeneity not captured through biopsy, and uptake was associated with immunotherapy response. Clinical trial registration no. NCT06754345 © The Author(s) 2026. Published by the Radiological Society of North America under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Lopci in this issue.