The immune system plays a critical role in cancer progression and antitumor responses. Glioblastoma is an aggressive and incurable brain tumor characterized by a highly immunosuppressive microenvironment. Over the past two decades, photodynamic therapy (PDT) has been evaluated as an adjunct to fluorescent-guided resection (FGR) and chemoradiotherapy according to the STUPP protocol, for resectable glioblastomas. In addition to demonstrating the feasibility of such a procedure, two previous clinical trials (INDYGO, NCT03048240; DOSINDYGO, NCT04391062) revealed/highlighted significant systemic immune changes following treatment, including modifications in peripheral blood mononuclear cells (PBMCs) activation and cytokine secretion profiles. However, the specific contribution of PDT remains uncertain due to the combined effects of, on the one hand, PDT and, on the other hand, FGR and chemoradiotherapy. This study aims to evaluate immune parameters in a control population undergoing FGR and chemoradiotherapy only (i.e., without PDT). The objective is to distinguish the immunological impact of PDT from that of FGR and chemoradiotherapy. The results will provide a better understanding of the systemic immune modulation induced by PDT in glioblastoma.