# Predictors of Survival in Patients Aged ≥70 with Glioblastoma: A Time-Dependent Multivariable Analysis

## TL;DR

This study finds that older patients with glioblastoma can benefit from combined surgery and therapy, with early treatment and complete tumor removal linked to longer survival.

## Contribution

The study identifies adjuvant chemoradiotherapy and gross total resection as key predictors of survival in elderly glioblastoma patients.

## Key findings

- Adjuvant chemoradiotherapy significantly improves survival in elderly glioblastoma patients.
- Complete tumor removal during surgery is associated with longer survival.
- Smoking history correlates with poorer survival outcomes in these patients.

## Abstract

Glioblastoma is an aggressive brain tumour with a very poor outlook, particularly in older patients, and its incidence is expected to rise as the population ages. This study reviewed the outcomes of 124 patients aged 70 years or older who underwent surgery for glioblastoma at a single specialist neurosurgical centre between 2021 and 2025, with the aim of identifying factors linked to survival. Overall survival remained limited, with a median survival of around 8 months. Two factors were clearly associated with longer survival. Patients who received chemotherapy and radiotherapy after surgery lived longer than those who did not, with the benefit being strongest in the early months following surgery and gradually reducing over time. In addition, patients in whom all visible tumour could be removed during surgery tended to live longer than those who had only partial tumour removal. In contrast, age within this older group, general fitness before surgery, the presence of other medical conditions, tumour size, and molecular tumour features did not show a clear link with survival. Notably, a history of smoking was associated with poorer survival, even after accounting for other factors. Taken together, these findings suggest that selected patients aged 70 and over can still benefit from active, combined treatment approaches, and that early, coordinated decision-making around surgery and post-operative therapy is important to maximise potential survival benefits in this growing patient group.

Background: Glioblastoma (GB) carries a dismal prognosis, with survival outcomes particularly poor in older patients. With the fastest-growing global demographic being those aged over 65, the incidence of GB is expected to rise. Objective: To evaluate predictors of survival in patients aged ≥70 years with histologically confirmed GB, focusing on surgical resection, adjuvant therapy, and comorbidities. Methods: A retrospective review was performed of all patients aged ≥70 undergoing index surgery for GB between January 2021 and March 2025 at a single tertiary neurosurgical centre. Demographics, pre-operative fitness scores (Karnofsky Performance Status [KPS]., Charlson Comorbidity Index [CCI].), tumour characteristics, extent of resection, adjuvant treatment, and survival were analysed. Tumour volume was estimated using the ABC/2 method. Survival outcomes were assessed using Kaplan–Meier curves and multivariable Cox proportional hazards regression. Results: A total of 124 patients aged ≥70 years (median 74 years, range 70–86) were included. Median overall survival was 8 months (IQR 4–15). On multivariable analysis, adjuvant chemoradiotherapy (HR = 0.30, 95% CI 0.17–0.52; p < 0.001) and gross total resection (GTR) (HR = 0.41, 95% CI 0.20–0.86; p = 0.019) were independently associated with improved survival. Smoking history was associated with increased hazard of death (HR = 2.02, 95% CI 1.07–3.81; p = 0.029), an effect robust to multiple sensitivity analyses. No significant associations were found for age, pre-operative KPS, comorbidity index, tumour volume, or methylation status (all p > 0.10). Tests for non-proportional hazards indicated that the survival benefit of adjuvant therapy diminished over time (interaction p = 0.0002), with early post-operative benefit (HR ≈ 0.35 at 1 month) that attenuated towards unity by 6–12 months. The effects of GTR and smoking were time-invariant. RMST analysis suggested a modest, non-significant absolute survival advantage of GTR over STR (mean difference = 2.0 months at 18 months; p = 0.11). After exclusion of early post-operative deaths (<6 weeks), adjuvant therapy (HR = 0.34; p < 0.001) and GTR (HR = 0.33; p = 0.005) remained independent predictors of improved survival. Conclusions: Among patients aged ≥70 years with glioblastoma, adjuvant therapy and extent of resection remain key independent predictors of survival, while smoking is associated with poorer outcomes. The survival benefit of adjuvant chemoradiotherapy is strongest in the early post-operative period and diminishes over time, underscoring the importance of early multidisciplinary intervention. These findings highlight that aggressive multimodal treatment may confer survival advantage even in older patients.