Understanding Glioblastoma in Older Patients Under WHO CNS 5

Glioblastoma represents the most frequent and aggressive primary brain malignancy encountered in adult neuro-oncology practice. Approximately half of all newly diagnosed patients present at age 65 years or older. Despite this substantial clinical burden, managing glioblastoma in older patients remains complicated by heterogeneous physiological reserve, multimorbidity, and evolving classification frameworks. The World Health Organization introduced the fifth edition of the Classification of Tumors of the Central Nervous System (WHO CNS 5), which refined diagnostic criteria by restricting glioblastoma exclusively to isocitrate dehydrogenase (IDH) wild-type astrocytic tumors. Consequently, real-world data reflecting contemporary histological and molecular definitions are essential to evaluate therapeutic decisions accurately.

Historically, older individuals have experienced significantly lower survival rates compared to younger cohorts. Clinicians often face a delicate dilemma when balancing aggressive multimodal interventions against treatment-related toxicities. Because definitions of chronological aging vary across global cancer registries, management paradigms differ widely between institutions. A comprehensive international cohort study established by the Histo-Mol GBM Collaborative analyzed 1,857 consecutive patients diagnosed in 2021 across 52 neuro-oncology centres. The primary objective was examining real-world treatment intensity, molecular characterization, and survival outcomes among older individuals diagnosed under contemporary criteria.

Variability in Treatment Intensity and Diagnostic Workup

Among the study cohort, 863 individuals (46.5%) were aged 65 years or older at the time of initial diagnosis. The investigators discovered clear disparities in diagnostic workup and therapeutic intensity between age brackets. Older adults frequently presented with compromised performance scores, which directly influenced the subsequent intensity of oncological interventions. Clinicians were less inclined to deliver standard trimodality protocols to elderly individuals. Instead, these patients received less intensive systemic therapy and localized radiation regimens.

Furthermore, comprehensive molecular testing occurred less frequently among senior adults. Tissue samples from older individuals were significantly less likely to undergo full epigenetic and genetic characterization, such as O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation analysis or broad next-generation sequencing. However, in patients who successfully underwent testing, the prevalence of key molecular markers did not differ significantly by age. This key finding suggests that lower diagnostic testing rates in senior adults reflect institutional practice biases rather than distinct biological variations. Consequently, standardized molecular evaluation remains vital across all age brackets to guide appropriate individualized therapy.

Surgical Resection versus Biopsy in Senior Populations

Surgical intervention forms the foundational pillar of management for suspected high-grade gliomas. Nevertheless, surgical strategies differ markedly between chronological age cohorts. In this international investigation, older adults were substantially more likely to undergo diagnostic biopsy alone rather than maximal safe surgical debulking. Frailty, deep anatomical tumor localization, and baseline neurological deficits often deter neurosurgeons from attempting extensive resections in elderly patients.

However, maximal safe resection provides significant cytoreductive and symptomatic advantages whenever feasible. Biopsy-only approaches were associated with reduced survival across all examined cohorts. While cautious decision-making protects patients from perioperative neurological morbidity, chronological age alone should not automatically preclude cytoreductive surgery. Instead, comprehensive preoperative functional assessments and advanced intraoperative mapping technologies help clinicians identify candidates who can safely tolerate extensive resection. Therefore, multidisciplinary neuro-oncology teams must carefully weigh surgical morbidity against the tangible survival benefits that safe debulking provides.

Chemoradiation Strategies and Survival Outcomes Across Age Brackets

Postoperative adjuvant protocols play a defining role in shaping disease progression and patient survival. Conventionally fractionated chemoradiation, consisting of 60 Gy delivered over six weeks with concurrent and adjuvant temozolomide, represents standard care for fit adult patients. In this international study, median overall survival declined progressively with advancing age, exhibiting the steepest reduction among individuals aged 70 years and older. However, a critical divergence emerged within the senior population when stratified by chronological age and functional status.

Patients aged 65 to 69 years derived comparable survival benefits from conventionally fractionated chemoradiation relative to younger adult cohorts. These findings indicate that individuals under age 70 with favorable functional status tolerate standard aggressive chemoradiation effectively. Conversely, for individuals aged 70 years and above, hypofractionated radiation courses combined with chemotherapy yielded more balanced survival and functional outcomes. Therefore, selecting radiotherapy regimens should incorporate both physiological fitness and refined chronological cutoffs rather than applying uniform age restrictions.

Molecular Profiling and Individualized Management Pathways

Molecular diagnostics serve as indispensable tools for guiding modern neuro-oncological management. Epigenetic silencing via MGMT promoter methylation confers heightened sensitivity to alkylating chemotherapy agents, particularly temozolomide. Given the higher risk of hematological toxicity and fatigue among older adults, determining MGMT methylation status provides actionable prognostic and predictive value. For senior patients harboring methylated tumors, adjuvant alkylating therapy offers meaningful survival extension that justifies systemic toxicity risks.

Conversely, older patients with unmethylated MGMT promoters derive limited clinical benefit from sustained temozolomide protocols. In such scenarios, clinicians can optimize supportive care, shorten adjuvant radiation regimens, and avoid prolonged cytotoxic exposure. The omission of routine molecular testing in senior adults inadvertently deprives clinicians of the objective data needed to make these nuanced treatment decisions. Ensuring equitable access to comprehensive molecular profiling ensures that senior patients receive tailored interventions aligned with tumor biology and patient resilience.

Clinical Implications for Multidisciplinary Neuro-Oncology Care

The findings from this large collaborative study provide clear, actionable insights for clinical neuro-oncology services globally. Managing glioblastoma in older patients necessitates moving away from generalized assumptions based purely on chronological age. Fit individuals aged between 65 and 69 years should not be arbitrarily denied standard chemoradiation regimens, as their survival benefits mirror those achieved in younger cohorts. For patients aged 70 years or older, hypofractionated radiation protocols offer an evidence-based alternative that preserves quality of life while maintaining therapeutic efficacy.

Moreover, modern clinical practice must integrate routine comprehensive geriatric assessment tools alongside functional scoring systems like the Karnofsky Performance Scale. Assessing baseline cognitive reserves, nutritional status, and polypharmacy enables clinical teams to predict treatment tolerance more reliably. Standardizing molecular workups across all age groups ensures that management plans reflect individual tumor biology. Through tailored surgical, radiological, and systemic strategies, multidisciplinary teams can optimize therapeutic efficacy while preserving essential neurocognitive function in older adults.

Frequently Asked Questions

What is the recommended radiotherapy approach for glioblastoma patients aged 65 to 69?

Fit patients aged 65 to 69 years with good performance status derive comparable survival benefits from conventionally fractionated chemoradiation (60 Gy over six weeks with temozolomide) relative to younger adults. Multidisciplinary teams should evaluate functional capacity rather than chronological age alone when selecting treatment intensity.

How should therapy be adjusted for glioblastoma patients aged 70 and older?

Patients aged 70 years and older generally experience superior balance between survival and quality of life using hypofractionated radiotherapy regimens (such as 40 Gy in 15 fractions) combined with temozolomide, especially when tumors exhibit MGMT promoter methylation, thereby minimizing prolonged treatment-related toxicity and functional decline.

Why is molecular testing critical in older glioblastoma patients?

Molecular testing, specifically assessing MGMT promoter methylation, identifies patients most likely to benefit from alkylating chemotherapy. In older populations vulnerable to treatment toxicity, these molecular insights prevent non-beneficial cytotoxic exposures in unmethylated cases while supporting aggressive adjuvant regimens in patients with methylated tumors.

Disclaimer: This content is for informational and educational purposes only. It is not intended to provide medical advice or to be a substitute for professional medical advice, diagnosis, or treatment. Patients should always consult their physician or other qualified healthcare provider regarding any questions about a medical condition. Healthcare professionals should exercise their independent clinical judgment and refer to the latest local and national guidelines for clinical practice.

References

1. Williams ST et al. Report of treatment intensity and survival outcomes in older patients with glioblastoma diagnosed according to WHO CNS 5 classification. J Neurooncol. 2026 Jun 04. doi: 10.1007/s11060-026-05628-x. PMID: 42240773.


2. Louis DN, Perry A, Wesseling P, et al. The 2021 WHO Classification of Tumors of the Central Nervous System: a summary. Neuro-Oncology. 2021;23(8):1231-1251. doi:10.1093/neuonc/noab106.


3. Perry JR, Laperriere N, O'Callaghan CJ, et al. Short-Course Radiation plus Temozolomide in Elderly Patients with Glioblastoma. N Engl J Med. 2017;376(11):1027-1037. doi:10.1056/NEJMoa1611977.