Hepner et al. showed an association between higher serum NFl and GFAP levels and disease progression in patients with CNS tumors versus patients with stable disease.37 On-treatment measurements of serum cytokines such TGFβ, IL10, and interferon γ could be informative as to the ongoing immunotherapy’s impact on the systemic immune system. Here, NEFL is linked to central nervous system neoplasm.