The frequency and inter-relationship of PD-L1 expression and tumour mutational burden across multiple types of advanced solid tumours in China

Abstract Background: PD-L1 expression and tumour mutational burden (TMB) have been demonstrated to be associated with the responses of multiple tumours to ICI therapy. Their prevalence and correlations in various types of advanced solid tumours from Chinese patients warrant further study. Methods: PD-L1 expression, TMB, PD-1+ Tils infiltration and the relationships among them were assessed in 6,668 advanced solid tumour specimens across 25 tumour types. The relationships among PD-L1 expression, TMB, PD-1+ Tils and CD8+ T cell infiltration and the therapeutic effect of PD-1 inhibitors were analysed in NSCLC samples.Results: PD-L1 expression and TMB varied widely among tumour types. PD-L1 expression and TMB was not significantly correlated within most cancer subtypes, and they showed only a small association across all specimens (Spearman R = 0.059). PD-1+ Tils infiltration was correlated with PD-L1 expression across all samples (Spearman R = 0.3056). However, PD-1+ Tils infiltration and TMB were not correlated. In NSCLC samples, CD8+ T cell infiltration was correlated with PD-1+ Tils infiltration and PD-L1 expression but not with TMB (Spearman R = 0.4117, 0.2045, 0.0007). Patients in the CR/PR group (anti-PD-1 therapy) had higher levels of PD-L1 expression, TMB, PD-1+ Tils and CD8+ T cell infiltration, and more patients in this group exhibited elevated levels of multiple biomarkers. Conclusions: Our results showed the PD-L1 expression and TMB in various types of advanced solid tumours in Chinese patients and their relationship with PD-1+ Tils and CD8+ T cell infiltration, which may inform ICI treatment.