Other studies have similarly demonstrated increased CD68+ cells in the rGBM microenvironment when comparing pre- and post-treatment glioma samples [3,18,60] and found it may be associated with decreased efficacy of immune checkpoint inhibitors, such as pembrolizumab anti-programmed cell death 1 (PD-1) [60] (Table 1). This evidence concerns the gene CD68 and central nervous system cancer.