Clinical significance of plasma PD-L1 + exosomes in the management of diffuse large B cell lymphoma

PD-L1 + exosome have been reported to be a promising prognostic biomarker in various cancers. However, its clinical value in diffuse large B cell lymphoma (DLBCL) has not been defined yet. In this study, a total of 165 plasma samples from 78 patients with DLBCL undergoing standard first-line R-CHOP regimens were collected at three different time points (pretreatment, and after 3 and 6 cycles of R-CHOP) to determine the proportions of PD-L1 + exosomes by flow cytometry. We found that high pretreatment plasma PD-L1 + exosome correlated with indicators of poor clinical outcome that included high Ki-67 expression ( P = 0.02), double expressor lymphoma ( P = 0.005), immunohistochemical PD-L1 + tumor tissue ( P = 0.006), and the baseline maximal standardized uptake values ( P = 0.0003). Pretreatment plasma PD-L1 + exosome was an independent factor by multivariate analysis with logistic regression ( P = 0.0301). Moreover, the pretreatment PD-L1 + exosome was a strong predictor of final treatment responses of either CR or non-CR by ROC analysis ( P < 0.001). PD-L1 + exosome level declined significantly in patients who experienced CR (pretreatment vs. after 3 cycles/after 6 cycles, P < 0.05), but not in the non-CR group. Intriguingly, plasma PD-L1 + exosome after 3 cycles (AUC = 0.857; 95%CI: 0.728–0.939) might represent a more sensitive indicator than radiographic assessment after 3 cycles (AUC = 0.626; 95%CI: 0.477–0.758) for evaluating the therapeutic response of DLBCL patients ( P = 0.0136). Our results suggest that plasma PD-L1 + exosomes may represent a new biomarker for the dynamic monitoring of treatment response.