Comprehensive Analysis of Chemotherapy and Targeted Therapy Outcomes in Recurrent Malignant Gliomas

Malignant gliomas represent the most common and aggressive category of primary malignant brain tumors in adults. Despite multimodal treatment approaches, the prognosis for patients with high-grade gliomas remains poor, with the vast majority ultimately developing disease progression or recurrence. When recurrence occurs, therapeutic options become limited and their efficacy modest. In recurrent glioblastoma, progression-free survival (PFS) and overall survival (OS) are measured in months, while in anaplastic astrocytomas (WHO grade 3-4), these outcomes similarly do not extend beyond one year after second-line therapy

While numerous clinical trials have investigated specific agents in selected populations, real-world data (RWD) on the sequential treatment of recurrent gliomas across multiple lines of therapy remain scarce. By design, these studies often enroll highly selected patients and may not fully represent the heterogeneous, heavily pretreated population encountered in routine clinical practice. Consequently, the comparative effectiveness of different chemotherapy regimens - including bevacizumab-containing schedules (e.g., with irinotecan), nitrosoureas, and platinum compounds - as they are used sequentially in the second, third, and subsequent lines is not well established. For the rare subset of patients harboring a BRAF mutation, targeted therapy with BRAF ± MEK inhibitors may represent an additional option, though real-world evidence in the recurrent setting remains limited. There is a particular lack of large-scale, real-world evidence on the cumulative impact of these sequential therapies on long-term outcomes such as overall survival and progression-free survival across multiple treatment episodes.

The GLIOTARG trial is designed to address this evidence gap. This large, single-center, retrospective and prospective observational cohort study aims to provide a comprehensive analysis of treatment patterns and clinical outcomes in a cohort of approximately 1000 patients with recurrent malignant gliomas treated at the N.N. Blokhin National Medical Research Center of Oncology between 2005 and 2025. By including only patients with molecularly confirmed diagnoses according to the WHO 2021 classification (including IDH-wildtype glioblastomas, IDH-mutant astrocytomas grade 3-4, and pleomorphic xanthoastrocytomas grade 2-3), this study ensures diagnostic precision and alignment with modern neuro-oncological standards.

The primary objective is to evaluate overall survival in a real-world clinical practice setting. Secondary objectives include assessing progression-free survival according to treatment modality, starting with the initial chemoradiotherapy (PFS1), followed by first-line (PFS2), second-line (PFS3), and subsequent lines of drug therapy. The study will specifically compare the efficacy of bevacizumab-containing regimens versus non-bevacizumab chemotherapies, investigate the role of BRAF ± MEK inhibitors in BRAF-mutant tumors, and analyze outcomes in rare histological subtypes such as pleomorphic xanthoastrocytomas. The ultimate goal is to provide a practical, evidence-based algorithm to guide the optimal sequencing of drug therapy in recurrent malignant gliomas, integrating clinical and molecular factors.

The study will pool comprehensive clinical, pathological, and treatment-related data from patients diagnosed with recurrent malignant gliomas over a 20-year period (2005-2025). Data to be collected for each patient will include:

• Demographics and Baseline Characteristics:

• Age at initial brain tumor diagnosis
• Sex (male/female)
• Clinical Presentation:

• Neurological symptoms at diagnosis (symptomatic, asymptomatic, unknown)
• Neurological syndromes at diagnosis (global cerebral symptoms (headache, nausea, vomiting, dizziness), aphasic, dysarthric, pyramidal, sensory, extrapyramidal, cerebellar/vestibulo-ataxic, bulbar, pseudobulbar, paroxysmal, cognitive, brainstem, visual, occlusive, behavioral, unknown)
• ECOG performance status at diagnosis (0-1, 2-3, unknown)
• Radiological features at diagnosis (present/absent/unknown): Multifocal disease, Corpus callosum involvement, Perifocal edema, Mass effect, Dislocation syndrome, Ventricular compression (lateral, III, IV), Brainstem compression, Intratumoral hemorrhage, Intratumoral necrosis, Occlusive hydrocephalus, Bone destruction, Cerebellar tonsil herniation
• Tumor Characteristics:

• Histological subtype (glioblastomas, astrocytomas and pleomorphic xanthoastrocytomas)
• Tumor grade (WHO grade 3, 4)
• Molecular-genetic diagnosis (according to WHO 2021 classification)

• IDH1 status (mutant/wildtype, specify mutation if applicable);
• IDH2 status (mutant/wildtype, specify mutation if applicable);
• BRAF mutation status (mutant/wildtype, specify mutation if applicable);
• 1p/19q codeletion status (present/absent);
• MGMT promoter methylation status (methylated/unmethylated).
• Initial Treatment:

• Neurosurgical intervention (yes/no);
• Extent of resection (biopsy < 30%, partial 30-75%, subtotal 75-90%, gross total > 90%);
• Chemoradiotherapy (yes/no);
• Radiotherapy modality (conventional fractionation, hypofractionation, stereotactic radiotherapy/radiosurgery);
• Dose per fraction (Gy);
• Total dose (Gy);
• Concurrent temozolomide during radiotherapy (yes/no);
• Response to radiotherapy (according to RANO 2.0: stable disease, partial response, complete response, progressive disease);
• Radiotherapy toxicity: radiation necrosis (yes/no), increased perifocal edema (yes/no).
• Drug Therapy Details (for each line of treatment):

• Line of therapy (first, second, third or fourth);
• Regimen (specify drugs);
• Treatment start and end date;
• Number of cycles administered;
• Best response on the line (according to RANO 2.0: stable disease, partial response, complete response, progressive disease);
• ECOG performance status before start of line;
• ECOG performance status after completion of line;
• Toxicity profile on the line (specify type and grade, if available);
• Date of progression on this line;
• Method of recurrence treatment after this line (drug therapy, surgery, radiotherapy, or combination)

Primary Endpoint - Overall Survival (OS): defined as the time from the date of initial brain tumor diagnosis to the date of death from any cause or last follow-up (censored).

Secondary Endpoints:

• Progression-Free Survival 1 (PFS1): defined as the time from the start of chemoradiotherapy to the date of documented intracranial progression according to RANO 2.0 criteria. Patients who proceeded directly to first-line drug therapy without evidence of progression will be censored at the start of first-line treatment.
• Progression-Free Survival 2 (PFS2): defined as the time from the start of first-line drug therapy to the date of documented intracranial progression according to RANO 2.0 criteria. Patients without documented progression will be censored at the date of last instrumental follow-up (Magnetic Resonance Imaging (MRI) or Positron Emission Tomography-Computed Tomography (PET-CT) with tyrosine/methionine)
• Progression-Free Survival 3 (PFS3): defined as the time from the start of second-line drug therapy to the date of documented intracranial progression according to RANO 2.0 criteria. Patients without documented progression will be censored at the date of last instrumental follow-up (MRI or PET-CT with tyrosine/methionine)
• Progression-Free Survival 4 (PFS4): defined as the time from the start of third-line drug therapy to the date of documented intracranial progression according to RANO 2.0 criteria. Patients without documented progression will be censored at the date of last instrumental follow-up (MRI or PET-CT with tyrosine/methionine)
• Progression-Free Survival 5 (PFS5): defined as the time from the start of fourth-line drug therapy to the date of documented intracranial progression according to RANO 2.0 criteria. Patients without documented progression will be censored at the date of last instrumental follow-up (MRI or PET-CT with tyrosine/methionine)

Statistical Analysis

• Descriptive Statistics. Baseline demographic, clinical, and molecular characteristics will be summarized using descriptive statistics. Categorical variables will be presented as frequencies and percentages. Continuous variables will be presented as medians with interquartile ranges (IQR) or means with standard deviations (SD), as appropriate based on data distribution. For variables with substantial missing data, the proportion of missingness will be reported, and patterns of missingness will be explored.
• Survival Analysis. Overall survival (OS) and progression-free survival for each treatment line (PFS1 through PFS5) will be estimated using the Kaplan-Meier method. Median survival times with corresponding 95% confidence intervals (CI) will be reported. Survival curves will be compared between clinically relevant subgroups using the log-rank test. Pre-specified subgroup analyses will be performed based on molecular markers (IDH1/2, BRAF, 1p/19q, MGMT), treatment modality (bevacizumab-containing regimens vs. non-bevacizumab chemotherapies), histological subtype (glioblastoma, anaplastic astrocytoma, anaplastic pleomorphic xanthoastrocytoma), extent of resection, radiotherapy modality, Eastern Cooperative Oncology Group (ECOG) performance status, radiological features, and neurological symptoms at diagnosis.
• Multivariable Analysis. To identify independent prognostic factors associated with OS and each PFS endpoint, Cox proportional hazards regression models will be constructed. Variables will be selected for inclusion in multivariable models based on clinical relevance and univariable screening (p < 0.10). Covariates will include age, sex, ECOG performance status, molecular markers (IDH1/2, MGMT, BRAF, 1p/19q), histological subtype, extent of resection, radiotherapy parameters, treatment regimen for each line, and number of lines of therapy received. Results will be presented as hazard ratios (HR) with 95% CI.
• Analyses in Rare Subgroups. For patients with rare histological subtypes (pleomorphic xanthoastrocytomas) and those harboring BRAF mutations receiving targeted therapy, descriptive analyses will be performed. Given the expected small sample sizes, these analyses will be primarily exploratory, with individual patient data presented and median survival times reported with 95% confidence interval (CI) where feasible.
• Software and Significance Level. All statistical analyses will be performed using R (version 4.0 or higher) and STATA 17.0. A two-sided p-value < 0.05 will be considered statistically significant. Adjustments for multiple comparisons will not be applied for exploratory analyses but will be considered for pre-specified subgroup comparisons.

Inclusion criteria

• Age ≥ 18 years at the time of initial brain tumor diagnosis;
• Histologically confirmed diagnosis of malignant glioma, including:

• Glioblastoma, IDH-wildtype (WHO grade 4)
• Astrocytoma, IDH-mutant (WHO grade 3-4)
• Pleomorphic xanthoastrocytoma (WHO grade 2-3)
• Molecularly confirmed diagnosis according to WHO 2021 classification (with available data on IDH1/2, BRAF, 1p/19q, and MGMT status where applicable);
• Documented disease recurrence or progression with available treatment-related data in medical records to assess at least one of the study outcome measures

Exclusion criteria

• Age < 18 years at initial diagnosis;
• Absence of molecular-genetic confirmation of the tumor (according to WHO 2021 classification);
• Lack of documented disease recurrence or progression, or insufficient treatment-related data in medical records to assess at least one of the study outcome measures;
• Prior participation in clinical trials with unblinded investigational agents where data cannot be extracted (except where data are available and verifiable);
• Synchronous primary malignant neoplasms.