Delayed Effect of Dendritic Cells Vaccination on Survival in Glioblastoma: A Systematic Review and Meta-Analysis

Dendritic cell vaccination (DCV) strategies, thanks to a complex immune response, may flare tumor regression and improve patients' long-term survival. This meta-analysis aims to assess the efficacy of DCV for newly diagnosed glioblastoma patients in clinical trials.

The study databases, including PubMed, Web of Knowledge, Google Scholar, Scopus, and Cochrane, were searched by two blinded investigators considering eligible studies based on the following keywords: "glioblastoma multiforme", "dendritic cell", "vaccination", "immunotherapy", "immune system", "immune response", "chemotherapy", "recurrence", and "temozolomide". Among the 157 screened, only 15 articles were eligible for the final analysis.

Regimens including DCV showed no effect on 6-month progression-free survival (PFS, HR = 1.385, 95% CI: 0.822-2.335, p = 0.673) or on 6-month overall survival (OS, HR = 1.408, 95% CI: 0.882-2.248, p = 0.754). In contrast, DCV led to significantly longer 1-year OS (HR = 1.936, 95% CI: 1.396-2.85, p = 0.001) and longer 2-year OS (HR = 3.670, 95% CI: 2.291-5.879, p = 0.001) versus control groups. Hence, introducing DCV could lead to increased 1 and 2-year survival of patients by 1.9 and 3.6 times, respectively.

Antitumor regimens including DCV can effectively improve mid-term survival in patients suffering glioblastoma multiforme (GBM), but its impact emerges only after one year from vaccination. These data indicate the need for more time to achieve an anti-GBM immune response and suggest additional therapeutics, such as checkpoint inhibitors, to empower an earlier DCV action in patients affected by a very poor prognosis.