Rapid early progression (REP) of glioblastoma is an independent negative prognostic factor: Results from a systematic review and meta-analysis

The role of GammaTile in the treatment of brain tumors: a technical and clinical overview

Malignant and benign brain tumors with a propensity to recur continue to be a clinical challenge despite decades-long efforts to develop systemic and more advanced local therapies. GammaTile (GT Medical Technologies Inc., Tempe AZ) has emerged as a novel brain brachytherapy device placed during surgery, which starts adjuvant radiotherapy immediately after resection. GammaTile received FDA clearance in 2018 for any recurrent brain tumor and expanded clearance in 2020 to include upfront use in any malignant brain tumor. More than 1,000 patients have been treated with GammaTile to date, and several publications have described technical aspects of the device, workflow, and clinical outcome data. Herein, we review the technical aspects of this brachytherapy treatment, including practical physics principles, discuss the available literature with an emphasis on clinical outcome data in the setting of brain metastases, glioblastoma, and meningioma, and provide an overview of the open and pending clinical trials that are further defining the efficacy and safety of GammaTile.

Prediction of Rapid Early Progression and Survival Risk with Pre-Radiation MRI in WHO Grade 4 Glioma Patients

Recent clinical research describes a subset of glioblastoma patients that exhibit REP prior to the start of radiation therapy. Current literature has thus far described this population using clinicopathologic features. To our knowledge, this study is the first to investigate the potential of conventional radiomics, sophisticated multi-resolution fractal texture features, and different molecular features (MGMT, IDH mutations) as a diagnostic and prognostic tool for prediction of REP from non-REP cases using computational and statistical modeling methods. The radiation-planning T1 post-contrast (T1C) MRI sequences of 70 patients are analyzed. An ensemble method with 5-fold cross-validation over 1000 iterations offers an AUC of 0.793 ± 0.082 for REP versus non-REP classification. In addition, copula-based modeling under dependent censoring (where a subset of the patients may not be followed up with until death) identifies significant features (p-value < 0.05) for survival probability and prognostic grouping of patient cases. The prediction of survival for the patients' cohort produces a precision of 0.881 ± 0.056. The prognostic index (PI) calculated using the fused features shows that 84.62% of REP cases fall under the bad prognostic group, suggesting the potential of fused features for predicting a higher percentage of REP cases. The experimental results further show that multi-resolution fractal texture features perform better than conventional radiomics features for prediction of REP and survival outcomes.

Study protocol: PreOperative Brain Irradiation in Glioblastoma (POBIG) - A phase I trial

Background

Glioblastoma is a high-grade aggressive neoplasm whose outcomes have not changed in decades. In the current treatment pathway, tumour growth continues and remains untreated for several weeks post-diagnosis. Intensified upfront therapy could target otherwise untreated tumour cells and improve the treatment outcome. POBIG will evaluate the safety and feasibility of single-fraction preoperative radiotherapy for newly diagnosed glioblastoma, assessed by the maximum tolerated dose (MTD) and maximum tolerated irradiation volume (MTIV).

Methods

POBIG is an open-label, dual-centre phase I dose and volume escalation trial that has received ethical approval. Patients with a new radiological diagnosis of glioblastoma will be screened for eligibility. This is deemed sufficient due to the high accuracy of imaging and to avoid treatment delay. Eligible patients will receive a single fraction of preoperative radiotherapy ranging from 6 to 14 Gy followed by their standard of care treatment comprising maximal safe resection and postoperative chemoradiotherapy (60 Gy/30 fr) with concurrent and adjuvant temozolomide). Preoperative radiotherapy will be directed to the part of the tumour that is highest risk for remaining as postoperative residual disease (hot spot). Part of the tumour will remain unirradiated (cold spot) and sampled separately for diagnostic purposes. Dose/volume escalation will be guided by a Continual Reassessment Method (CRM) model. Translational opportunities will be afforded through comparison of irradiated and unirradiated primary glioblastoma tissue.

Discussion

POBIG will help establish the role of radiotherapy in preoperative modalities for glioblastoma.

Trial registration

NCT03582514 (clinicaltrials.gov).

[Early progression of glioblastoma before radiotherapy]

OBJECTIVE

To analyze the influence of continued growth of glioblastoma between surgery and radiotherapy on subsequent survival.

MATERIAL AND METHODS

Fractionation with a prescribed dose of 2 and 3 Gy was alternately applied using a pairwise modeling strategy in 140 patients with morphologically confirmed glioblastoma (grade 4). Early progression of disease between microsurgery and radiotherapy was diagnosed in 60 patients, and no tumor growth was noted in 80 patients.

RESULTS

The minimum period of early progression was 0.33 months, maximum - 4.27 months (median 1.1 (95.0% CI: 0.9-1.3)). The most significant predictors of early progression were resection quality (p<0.0001), large residual tumor (p=0.003) and no MGMT promoter methylation (p=0.001). IDH1 status did not affect early progression. In residual tumor ≥1.2 cm3, the median period of early progression was 1.9 months (n=70; 95% Cl: 1.3-2.5), <1.2 cm3 - 3.5 months (n=70; p=0.019). After resection of less than 76% of tumor, this value was 1.1 months (n=28), ≥76% - 3.1 months (n=112; p=0.006). Without tumor growth, the median overall survival was 33.41 months (n=80; 95% Cl: 27.1-39.7), with early progression - 16.03 months (n=60; 95% Cl: 13.5-18.6; p<0.0001). This predictor was significant for fractionation with a prescribed dose of 3 Gy (p<0.0001) and standard radiotherapy (2 Gy; p=0.028). By December 2022, 26 out of 40 patients without early progression survived two years after treatment (3 Gy) (65%, median not reached). In case of fractionation with a prescribed dose of 2 Gy, 20 patients survived this period (50%, median reached).

CONCLUSION

Almost half of patients with newly diagnosed glioblastoma develop early progression between microsurgery and radiotherapy. Therefore, patients with and without early progression should be probably assigned to different prognostic groups regarding overall survival.

[Extent of resection in patients with glioblastoma]

OBJECTIVE

To investigate the impact of resection quality on subsequent survival of patients with glioblastoma.

MATERIAL AND METHODS

There were 141 patients with morphologically confirmed glioblastoma (grade 4). Fractionation with the prescribed dose of 2 and 3 Gy was alternately used (pairwise modeling strategy). Total resection was performed in 29.8% of patients (EOR: 100%; n=42), subtotal - 56.7% (EOR: 70-99%; n=80). Extent of resection 1-69% was registered in 19 patients (13.5%).

RESULTS

As of December 2022, 124 out of 141 patients (87.9%) were diagnosed with primary progression, 101 (71.6%) ones died. We analyzed the threshold role of EOR. The most informative level was 70% (p=0.002). EOR 100% was followed by median overall survival about 32.2 months (95% Cl: 15.3-49.1), EOR 70-99% - 21.3 months (95% Cl: 15.1-27.5), EOR 1-69% - 10.3 months (95% Cl: 3.8-16.9; p=0.003). Fractionation mode with the prescribed dose of 3 Gy partially eliminated significance of EOR (p=0.148) in contrast to standard fractionation (p=0.015). Tumor growth in the interval between surgery and radiotherapy (REP) reduces significance of EOR (p=0.042). Inclusion of second-line therapy with bevacizumab in multivariate analysis model (OR=0.488; p=0.002) makes EOR less significant (OR=0.749; p=0.085) in contrast to REP (OR=2.482; p<0.0001).

CONCLUSION

To date, the principle of maximum safe resection remains fundamental in neurosurgery. EOR about 70% is sufficient regarding overall survival, but total resection should be sought if possible.

Visualising spatial heterogeneity in glioblastoma using imaging habitats

Glioblastoma is a high-grade aggressive neoplasm characterised by significant intra-tumoral spatial heterogeneity. Personalising therapy for this tumour requires non-invasive tools to visualise its heterogeneity to monitor treatment response on a regional level. To date, efforts to characterise glioblastoma's imaging features and heterogeneity have focussed on individual imaging biomarkers, or high-throughput radiomic approaches that consider a vast number of imaging variables across the tumour as a whole. Habitat imaging is a novel approach to cancer imaging that identifies tumour regions or 'habitats' based on shared imaging characteristics, usually defined using multiple imaging biomarkers. Habitat imaging reflects the evolution of imaging biomarkers and offers spatially preserved assessment of tumour physiological processes such perfusion and cellularity. This allows for regional assessment of treatment response to facilitate personalised therapy. In this review, we explore different methodologies to derive imaging habitats in glioblastoma, strategies to overcome its technical challenges, contrast experiences to other cancers, and describe potential clinical applications.