Glioblastoma (GBM) is the most common and aggressive adult primary brain tumor and remains associated with poor outcomes despite multimodality therapy.[1, 2] Population-based U.S. registries report a consistent annual age-adjusted incidence near , with diagnosis concentrated in older adults (median age years) and a marked male predominance.[2, 3] Contemporary diagnosis integrates histology with molecular criteria, and the 2021 WHO CNS5 classification restricts the term “glioblastoma” to diffuse astrocytic gliomas that are IDH-wildtype and H3-wildtype and that show necrosis/microvascular proliferation and/or specific molecular alterations such as TERT promoter mutation, EGFR amplification, or +7/−10 copy-number changes.[4–6] At the molecular level, GBM is characterized by frequent alterations involving RTK/RAS/PI3K, TP53, and RB pathway circuitry, with additional recurrent events involving EGFR and telomere biology (e.g., frequent TERT promoter mutation).[5, 7] Median overall survival with current standard-of-care therapy is typically months and long-term survival remains uncommon, with 5-year survival generally reported as <5–6%.[1, 2, 5, 8] Tumor treating fields (TTFields) are associated with improved survival when added to standard-of-care, including pooled hazard ratios for overall survival near in meta-analytic synthesis, with adherence (≥75% usage) associated with additional benefit.[9] Emerging approaches—including immune checkpoint blockade, CAR T cells targeting EGFRvIII/IL13Rα2, oncolytic virotherapy (DNX-2401), and dendritic-cell vaccines (DCVax-L)—show signals of activity in selected settings, including long-term survivors in early studies, but have not yet overcome core challenges such as an immunosuppressive (“cold”) microenvironment and intratumoral heterogeneity.[10–13]
Introduction
Glioblastoma (GBM) is widely characterized as the most common and most aggressive malignant primary brain tumor in adults, and it constitutes a major source of morbidity and mortality among central nervous system cancers.[1, 14] Even with multimodality treatment paradigms incorporating surgery, radiotherapy, and systemic therapy, the overall prognosis remains poor and durable long-term survival is rare in population-level analyses and clinical summaries.[1, 2]
Epidemiology
Glioblastoma imposes a substantial population burden, and it is described as the most common and aggressive of brain tumors, accounting for about 14.2% of brain tumors in one cited summary.[1] In U.S. registry-based analyses, the annual age-adjusted incidence is consistently near persons (e.g., 3.19/100,000 and 3.21/100,000), with a median age at diagnosis around 64 years in multiple sources.[2, 3, 5]
Incidence increases steeply with age and peaks in older adults, with registry reports describing a peak at ages 75–84 years and a decline after age 85 years.[3] Another estimate similarly notes that incidence increases beyond age 40 years and peaks between ages 75 and 84 years at 15.30 per 100,000 population.[6]
Sex differences are consistent across U.S. datasets, with male incidence exceeding female incidence (e.g., 3.97 vs 2.53 per 100,000), and one registry summary reporting that glioblastoma is 1.58 times more common in males than females (4.00 vs 2.53 per 100,000).[2, 3]
Race/ethnicity patterns are reported in population data, including higher incidence among Whites compared with Asians and Blacks in one SEER-based analysis (3.43 vs 1.417 vs 1.724).[15] In additional analyses, incidence in Blacks, Asians/Pacific Islanders, and American Indians/Alaskan Natives is reported as substantially lower than in non-Hispanic Whites (one-fourth to one-half for GBM).[16] A separate report similarly notes highest incidence in non-Latino Whites and significantly lower incidence in Latino Whites and Blacks.[17]
Temporal trends vary by period, but SEER-based analyses have reported increasing incidence in Whites over 1992–2015 (APC=0.51%).[15] Another analysis reports more rapid increases from 1978–1992 (APC=2.9%) with slower growth during 1992–2018 (APC=0.2%).[18]
Risk-factor evidence in the provided sources identifies ionizing radiation exposure as the single known environmental risk factor for GBM.[19] In registry-based survival modeling, all-cause mortality associations include age, calendar year of diagnosis, sex, treatment receipt, tumor size, tumor location, extent of resection, median household income, and race.[20]
Pathology and Classification
Gliomas have historically been graded by WHO into grades I–IV based on malignancy level determined by histopathologic criteria.[5] Within this framework, GBM is a high-grade (grade IV) glioma with angiogenesis, robust proliferation, and a characteristic necrotic lesion described as “pseudopalissading necrosis,” alongside microvascular proliferations often related to thrombosis.[21]
The WHO classification has evolved toward integrated diagnoses that incorporate molecular information alongside histopathology, and the 2016 revision is described as restructuring glioma classification with incorporation of molecular features in addition to histopathologic appearance.[2] In this context, determination of IDH mutation status was included as a key diagnostic component, resulting in distinct subgroups in earlier frameworks.[2]
In 2021, the WHO updated the classification of CNS tumors in a way that restricts glioblastoma to IDH-wildtype tumors, with the stated goal of improving understanding of prognosis and optimal therapy and enabling more homogeneous clinical trial populations.[22] In WHO CNS5, glioblastoma is defined as a “diffuse, astrocytic glioma that is IDH-wildtype and H3-wildtype” and that has one or more of microvascular proliferation, necrosis, TERT promoter mutation, EGFR gene amplification, or +7/−10 chromosome copy-number changes (CNS WHO grade 4).[4] Consistent with this redefinition, IDH-mutant tumors are described as no longer being classified as glioblastoma within the WHO CNS5 framework.[23]
Practical diagnostic categories used in recent studies include “histologic GBM” (IDH-wildtype/H3-wildtype diffuse gliomas with microvascular proliferation and/or intratumoral necrosis) and “molecular GBM” (IDH-wildtype/H3-wildtype diffuse gliomas that meet molecular criteria such as TERT promoter mutation, EGFR amplification, or +7/−10).[24] This integrated approach implies that a glioblastoma diagnosis can be supported by either classic histologic hallmarks or by defining molecular alterations even when typical histology is not present.[4, 5]
Molecular Biology
Glioblastoma biology is anchored by the central discriminator of IDH status, with IDH1/IDH2 mutations reported in 70–80% of low-grade glioma and secondary GBM but only 5–10% of primary GBM.[3] IDH1 mutation is associated with better outcomes and is described as a reliable objective molecular marker for secondary GBM over clinical and pathologic criteria in the provided sources.[3] In WHO-integrated concepts, only IDH-wildtype gliomas can be classified as molecular glioblastoma regardless of histologic grade, aligning with the WHO 2021 restriction of glioblastoma to IDH-wildtype disease.[22, 25]
At the pathway level, a cited integrated analysis groups genetic lesions into three main signaling routes, including RTK/RAS/PI3K altered in almost 88% of GBMs, TP53 pathway altered in 87% of GBMs, and RB signaling altered in approximately 78% of GBMs.[5] Tumor suppressor alterations such as TP53 and PTEN are described as commonly observed, together with EGFR amplification and aberrant RTK–RAS–PI3K signaling.[25] Consistent with these summaries, TCGA sequencing analyses identified somatic alterations in TP53 (78%), RB1 (87%), and RTK/RAS/PI3K signaling pathways (88%), with these alterations present in 74% of tumors.[25]
EGFR biology is a frequent hallmark, with >40% of GBMs exhibiting EGFR amplification in one summary and with EGFRvIII described as a deletion mutant that produces constitutive signaling essential for tumor growth.[26] EGFRvIII expression is reported in 24–67% of glioblastomas and not in normal tissues in the provided sources, supporting its relevance as an immunotherapy target.[27]
Telomere biology is also prominent, with TERT promoter mutations reported at high frequency (e.g., 76.6% in one cohort), and such mutations are described as more common in primary versus secondary GBMs and inversely correlated with IDH1/2 mutations.[7] Mechanistically, TERT promoter mutations are thought to unmask ETS-family transcription-factor binding sites, upregulating TERT expression and telomerase activity in the cited description.[7]
MGMT promoter methylation is emphasized as the most predictive and prognostic molecular biomarker in IDH-wildtype glioblastoma, with one review stating that roughly 40% of IDH-wildtype glioblastomas are methylated.[6] A pooled analysis of five phase III trials reports median overall survival of approximately 24 months in MGMT-methylated patients compared with 14 months in unmethylated counterparts.[6] MGMT promoter methylation is also described as an independent prognostic marker for overall survival, with more than 90% of longer-term surviving patients having MGMT promoter methylation/hypermethylation in one cited source.[4] Lack of MGMT promoter methylation is associated with resistance to temozolomide in the provided sources.[4]
Multiple sources describe glioblastoma stem-like cells (GSCs) and niche biology, including preferential residence of brain tumor stem-like cells in the perivascular niche.[28] Increased endothelial cells are reported to expand the stem-like fraction, whereas in vivo blood vessel depletion by anti-angiogenic agents slowed tumor growth and decreased counts of self-renewing and multipotent cells in one cited report.[28] Spatial niche descriptions distinguish cells wrapping vessels (perivascular niches) from cells around circumscribed necroses (perinecrotic niches).[29]
The tumor microenvironment is described as immunologically “cold,” enriched with immunosuppressive cytokines (including TGF-β, IL-6, IL-10) and immune regulatory cells (including Tregs, M2 macrophages, myeloid-derived suppressor cells, and tumor-associated macrophages) that disable effective CD8+ T-cell and NK-cell responses.[12] PD-L1 is reported as upregulated in the GBM microenvironment and appears more associated with the mesenchymal subtype in the cited description.[28]
Prognosis
Glioblastoma has persistently poor outcomes despite therapeutic advances, and long-term survival is described as rare in clinical summaries of multimodality care.[1, 2] Median survival is commonly summarized as approximately 14–15 months from diagnosis in multiple sources, and one report similarly states a median survival of 15 months.[5, 8] In untreated patients, one source reports a median survival of only 3 months, emphasizing the lethality of the disease without effective therapy.[3]
Long-term survival remains uncommon in population-level summaries, with statements that fewer than 5% survive 5 years following diagnosis and that less than 5% have 5-year or more overall survival in cited sources.[1, 3] Registry-focused summaries similarly report that despite incremental improvements in shorter-term survival over time, 5-year survival remains relatively constant with a survival rate of 5.8% at 5 years postdiagnosis in one report.[2] At the same time, relative survival analyses show improvement over decades, including a reported increase in 1-year relative survival from 26.18% (1975–1979) to 44.90% (2017).[18]
Prognosis is heterogeneous and is influenced by patient and disease characteristics in multivariable models, including age as a strong adverse factor (e.g., aging HR 1.030 per year in one model).[30] In the same analysis, extent of disease and distant extent of disease were associated with worse survival (e.g., HR 1.383 and HR 1.500, respectively).[30] Factors associated with improved survival in that analysis included Asian or Pacific Islander race (HR 0.769), married status (HR 0.905), and unilateral tumor location (HR 0.858).[30]
Molecular features also stratify prognosis, with replicated findings that IDH1-mutant disease is associated with improved survival (e.g., 45.6 months vs 13.2 months OS in one cited report).[8] MGMT promoter methylation is similarly highlighted as a major prognostic determinant and a predictor of temozolomide sensitivity, with lack of methylation associated with resistance to temozolomide.[4]
Current Treatment
Current standards of care for glioblastoma incorporate multimodality therapy including resection, radiation, and chemotherapy in clinical summaries and registry discussions.[2, 27] A key benchmark from the temozolomide-era standard of care is a median overall survival of 14.6 months reported for “resection, radiation, and chemotherapy” in one cited source (Stupp et al., 2005).[27]
Device-based therapy with TTFields has been associated with improved survival when added to standard-of-care in pooled evidence, with one meta-analysis reporting significantly longer overall survival for TTFields plus standard-of-care versus standard-of-care alone (HR 0.63; 95% CI 0.53–0.75; P<0.001).[9] In the same synthesis, average recommended device usage of ≥75% was associated with prolonged overall survival compared with <75% usage (pooled HR 0.60; 95% CI 0.48–0.73; P<0.001).[9]
To summarize key quantitative benchmarks reported across standard and TTFields-augmented care, the table below consolidates common endpoints and effect sizes described in the provided sources.
Emerging Therapies
Multiple emerging strategies seek to improve outcomes in glioblastoma, including immunotherapy, engineered cellular therapies, oncolytic viruses, and therapeutic vaccines, reflecting the need for improved approaches given persistently poor prognosis with current standards.[2, 26] The immunosuppressive, “cold” microenvironment described for GBM provides a biological rationale for combinations that attempt to overcome ineffective antitumor immunity.[12]
Immune checkpoint inhibition has shown limited efficacy in recurrent disease in at least one phase III comparison, as CheckMate 143 reported that nivolumab monotherapy did not improve overall survival compared with bevacizumab in recurrent glioblastoma previously treated with chemotherapy and radiotherapy.[10] In the same cited summary, nivolumab had median PFS of 1.5 months versus 3.5 months with bevacizumab, and median OS of 9.8 months versus 10.0 months, with objective response rates of 8% versus 23%.[10]
Engineered cellular therapies have focused on tumor-associated antigens such as EGFRvIII, which is reported in 24–67% of glioblastomas and not in normal tissues in the cited sources.[27] Preclinical work also describes EGFRvIII as a common variant occurring in about 30% of patients with glioblastoma in one cited description, supporting its ongoing use as an immunotherapy target in development.[31]
Oncolytic virotherapy has produced signals of durable survival in subsets, including reports that 20% of patients with recurrent glioblastoma survived for at least three years after a single injection of the oncolytic adenovirus DNX-2401 in one cited report.[11] A related report similarly describes that 20% of patients survived more than 3 years from treatment and that at least three patients showed >95% reduction in enhancing tumor resulting in >3 years of progression-free survival in one arm.[32] Another cited summary reports four patients surviving more than 18 months with two long-term survivors exceeding 4.5 years following DNX-2401-based treatment in recurrent settings.[33]
Therapeutic vaccination strategies include dendritic cell–based approaches, with DCVax-L reporting a median overall survival of 23.1 months (95% CI 21.2–25.4) in an intention-to-treat population in one cited report.[12] A separate evidence synthesis reports that dendritic cell vaccination (DCV) was associated with longer 1-year overall survival (HR 1.936; 95% CI 1.396–2.85; p=0.001) and longer 2-year overall survival (HR 3.670; 95% CI 2.291–5.879; p=0.001), while also concluding that impact emerges only after one year from vaccination.[13] Additional cited trial summary text reports that for newly diagnosed GBM receiving DCVax-L in addition to standard-of-care, PFS was around 24.0 months and OS was 36.0 months, with favorable safety and only mild (grade I/II) side effects in that report.[34]
Future Directions and Challenges
The persistent lethality of glioblastoma despite ongoing therapeutic advancements has been explicitly noted as motivating the need for improved understanding of tumor biology in the provided sources.[26] The WHO 2021 classification revision is described as enabling more homogeneous patient populations for clinical trials, which supports biomarker-driven evaluation of novel therapies within better-defined entities.[22]
Biology-driven challenges emphasized in the sources include the role of glioblastoma stem-like cells and their niche dependence, as stem-like cells are reported to preferentially reside in perivascular niches and to be influenced by endothelial-cell abundance in ways that can modulate tumor growth and self-renewal capacity.[28] The immunologically “cold” tumor microenvironment enriched for immunosuppressive cytokines and regulatory immune cells provides an additional barrier to effective immune surveillance and helps contextualize limited checkpoint inhibitor efficacy in recurrent disease.[10, 12]
Given these constraints, a forward-looking implication supported by the cited materials is that successful strategies are likely to require (i) precise molecular classification for trial enrollment and prognostic interpretation and (ii) rational combinations designed to address niche-driven resistance and immune suppression, rather than reliance on single agents in broadly defined populations.[12, 22, 28]
Conclusions
Glioblastoma remains a high-incidence, highly lethal adult brain tumor with U.S. incidence near per year, older age at diagnosis, and male predominance in registry datasets.[2, 3] The WHO CNS5 framework now defines glioblastoma as an IDH-wildtype, H3-wildtype diffuse astrocytic glioma with grade-4 histology and/or defining molecular features, improving diagnostic precision and supporting more consistent prognostic interpretation.[4, 23] Molecular determinants such as IDH mutation and MGMT promoter methylation stratify outcomes, while median overall survival remains typically months and 5-year survival is generally <5–6% in cited summaries.[2, 4, 5, 8] TTFields demonstrate an evidence-based survival association (e.g., pooled for OS) when added to standard-of-care, and emerging modalities such as DNX-2401 and dendritic cell vaccines show encouraging signals in subsets, including long-term survivors and extended median OS in select reports.[9, 11, 12] However, the immunosuppressive microenvironment and stem-like cell niche biology highlighted in the cited literature underscore the need for biomarker-driven, combination strategies to achieve durable population-level benefit.[12, 28]
