5255 - [18F]-FDG PET/CT in predicting PD-L1 status in nasopharyngeal carcinoma

Background

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.

Methods

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.

Results

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 SUV_max (P = 0.003) and TLG (P = 0.001), while PD-L1 expression in TIIC was negatively associated with SUV_max (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%.

Conclusions

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.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.