PD-L1 Expression in Cutaneous Angiosarcomas: A Systematic Review with Meta-Analysis.

Cutaneous angiosarcoma (CAS) is the most common type of angiosarcoma that predominantly affects older Caucasians. The outcomes of immunotherapy in CAS are currently under investigation in relation to the expression of programmed death ligand 1 (PD-L1) and other biomarkers. We performed a systematic review and metanalysis of data from the current literature reporting on PD-L1 immunohistochemistry expression. A systematic search of publications in the electronic databases PubMed, Web of Science, and Scopus was conducted using the following terms: "PD-L1" and "angiosarcomas". A total of ten studies reporting on 279 cases were identified and included in the meta-analysis. The pooled prevalence of PD-L1 expression in CAS was 54% (95% CI 36-71%), with high heterogeneity (I 2 = 84.81%, p < 0.001). In sub-group analysis, the proportion of PD-L1 expression in CAS was significantly ( p = 0.049) lower in Asian studies (ES = 35%, 95% CI 28-42%, I 2 = 0.0%, p = 0.46) than in European studies (ES = 71%, 95% CI 51-89%, I 2 = 48.91%, p = 0.12).