Relationship between the expression of PD-1/PD-L1 and ¹⁸F-FDG uptake in bladder cancer

Immunotherapy aimed at inhibiting the PD-1/PD-L1 immune checkpoint has been approved and used successfully for the treatment of bladder cancer. The identification of markers predictive of response to immune checkpoint inhibitors is critical to advancing the success of this therapy. ¹⁸F-FDG PET/CT is a molecular imaging technique that can provide phenotypic information on malignant tumours. It is currently unknown whether there is a relationship between ¹⁸F-FDG uptake and expression of PD-1/PD-L1 in bladder cancer. In this study, we investigated whether PD-1/PD-L1 expression is associated with ¹⁸F-FDG uptake in bladder cancer, and whether ¹⁸F-FDG PET/CT imaging can be used to predict the PD-1/PD-L1 status of bladder cancer.

A retrospective analysis was performed in 63 patients with bladder cancer who had undergone ¹⁸F-FDG PET/CT before surgical resection. Maximum standardized uptake values (SUVmax) were determined.

SUVmax was significantly higher in PD-1-positive patients than in PD-1-negative patients (33.0 ± 13.9 and 19.6 ± 14.2, respectively; P = 0.032), and in PD-L1-positive patients than in PD-L1-negative patients (29.1 ± 15.6 and 15.8 ± 11.4, respectively; P < 0.0001). In a multivariate analysis SUVmax was significantly associated with both PD-1 expression and PD-L1 expression (P = 0.021 and P = 0.003, respectively). Using a SUVmax cut-off value of 22.7, PD-1 status and PD-L1 status could be predicted with accuracies of 71.4% and 77.8%, respectively.

Higher ¹⁸F-FDG uptake by bladder cancer is associated with elevated PD-1/PD-L1 expression. ¹⁸F-FDG PET/CT may be useful for predicting the PD-1/PD-L1 status of bladder cancer and for determining the optimal therapeutic strategy.