PD-1/PD-L1 blockades have shown promising antitumor activity in clinical trials of advanced nasopharyngeal carcinoma (NPC). Being the most wildly used molecular imaging in clinic, 18F-FDG PET/CT provides multiple information of tumor biology. In this study, we investigated the association of PD-L1 expression with 18F-FDG uptake and clinical features in patients with NPC.
84 patients were initially histopathologically diagnosed with NPC between December 2016 and March 2019. All tissue specimens and PET/CT images were collected before any treatment. The PD-L1 antibody we used in this investigation was SP263 (Ventana, USA). High PD-L1 expression in tumor cells (TC) or tumor-infiltrating immune cells (TIIC) was defined as ≥ 50% of corresponding cells with membranous staining.
The values of tumor SUVmax and TLG in patients with positive TC PD-L1 expression were significantly higher than those of negative TC PD-L1 expression (SUVmax: 10.3±4.1 vs. 6.9±3.2; P < 0.001; TLG: 77.7±64.5 vs. 35.0±20.5; P < 0.001), while the SUVmax values and TLG in patients with positive TIIC PD-L1 expression is lower than those of negative TIIC PD-L1 expression (SUVmax: 7.0±3.4 vs. 9.7±4.1; P = 0.011; TLG: 29.1±14.4 vs. 71.3±61.2; P = 0.001). Univariate analysis showed that the expression of PD-L1 in TC was associated with tumor T stage (P = 0.044) but not with serum Epstein-Barr virus (EBV) load (P = 0.816). On the other hand, the expression of PD-L1 in TIIC was related to both T stage (P = 0.028) and serum EBV load (P = 0.003). In multivariate logistic regression analysis, PD-L1 expression in TC was positively associated with tumor SUVmax (P = 0.003) and TLG (P = 0.001), while PD-L1 expression in TIIC was negatively associated with SUVmax (P = 0.038) and serum EBV load (P = 0.025). Through the ROC curve, the SUVmax cut-off value of 6.7 and the TLG cut-off value of 41.3 can be used to predict the PD-L1 status in TC with an accuracy of 78.6% and 71.4%, while the SUVmax cut-off value of 7.2 can be used to predict the PD-L1 status in TIIC with an accuracy of 72.6%.
18F-FDG uptake with NPC lesions were positively correlated with PD-L1 expression in TC and negatively correlated with PD-L1 expression in TIIC. 18F-FDG PET / CT imaging may be useful for predicting the PD-L1 status in patients with NPC.
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All authors have declared no conflicts of interest.