Purpose: Immunotherapy has been successfully utilized for treatment of gastric cancer, so the identification of clinicopathologic features that are predictive of response to this therapy is crucial. 18F-FDG PET/CT can provide information on the molecular phenotype of many malignant tumors. The correlation between 18F-FDG accumulation and PD-L1/PD-L1-TILs status in gastric cancer patients has not been investigated. The aim of the current study is to assess whether 18F-FDG accumulation is associated with PD-L1/PD-L1-TILs status, and whether 18F-FDG PET/CT may be useful for predicting PD-L1/PD-L1-TILs expression of gastric cancer.

Results: Tumors with positive PD-L1 expression had higher SUVmax than in tumors with negative PD-L1 expression (15.0 ± 8.0 vs. 7.2 ± 4.2, respectively; P = 0.004). Tumors with positive PD-L1-TILs expression also had higher SUVmax than in tumors with negative PD-L1-TILs expression (10.3 ± 6.5 vs. 6.6 ± 3.7, respectively; P = 0.034). Multivariate analysis suggested that SUVmax remained significantly correlated with the status of PD-L1 (P = 0.043) and PD-L1-TILs (P = 0.016). PD-L1 expression was predicted with an accuracy of 67.2% when a SUVmax value of 8.55 was used as a cutoff point for analysis. Similarly, PD-L1-TILs expression was predicted with an accuracy of 64.2%, when a SUVmax value of 7.9 was used as the threshold for analysis.

Conclusion: Higher 18F-FDG accumulation in gastric cancers is correlated with positive PD-L1/PD-L1-TILs expression. 18F-FDG PET/CT may be used to predict the status of PD-L1/PD-L1-TILs and thus aid in optimal treatment decision.

Methods: A retrospective analysis was conducted on 64 patients with gastric cancer who underwent 18F-FDG PET/CT. SUVmax was calculated from the 18F-FDG accumulation of the primary tumor. The relationship between SUVmax and PD-L1/PD-L1-TILs status was analyzed.