Using Smaller-Than-Standard Radiation Treatment Margins Does Not Change Survival Outcomes in Patients with High-Grade Gliomas

Clinical research framework proposal for ketogenic metabolic therapy in glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults, with a universally lethal prognosis despite maximal standard therapies. Here, we present a consensus treatment protocol based on the metabolic requirements of GBM cells for the two major fermentable fuels: glucose and glutamine. Glucose is a source of carbon and ATP synthesis for tumor growth through glycolysis, while glutamine provides nitrogen, carbon, and ATP synthesis through glutaminolysis. As no tumor can grow without anabolic substrates or energy, the simultaneous targeting of glycolysis and glutaminolysis is expected to reduce the proliferation of most if not all GBM cells. Ketogenic metabolic therapy (KMT) leverages diet-drug combinations that inhibit glycolysis, glutaminolysis, and growth signaling while shifting energy metabolism to therapeutic ketosis. The glucose-ketone index (GKI) is a standardized biomarker for assessing biological compliance, ideally via real-time monitoring. KMT aims to increase substrate competition and normalize the tumor microenvironment through GKI-adjusted ketogenic diets, calorie restriction, and fasting, while also targeting glycolytic and glutaminolytic flux using specific metabolic inhibitors. Non-fermentable fuels, such as ketone bodies, fatty acids, or lactate, are comparatively less efficient in supporting the long-term bioenergetic and biosynthetic demands of cancer cell proliferation. The proposed strategy may be implemented as a synergistic metabolic priming baseline in GBM as well as other tumors driven by glycolysis and glutaminolysis, regardless of their residual mitochondrial function. Suggested best practices are provided to guide future KMT research in metabolic oncology, offering a shared, evidence-driven framework for observational and interventional studies.

miR-200 family as new potential prognostic factor of overall survival of patients with WHO G2 and WHO G3 brain gliomas

Gliomas are the predominant cause of cancer-related deaths among the young population. Even after incorporation of IDH1/2 mutations and 1p19q codeletion there are doubts regarding adjuvant treatment in WHO G2/G3 gliomas. miRNA molecules control about 30% of all genes, also many oncogenes, tumor suppressor genes and genes responsible for the response to ionizing radiation and systemic treatment. Patients with brain gliomas exhibit miRNA disorders. We aimed to evaluate the expression of miR-200 family members in relation to selected clinico-pathological factors and their prognostic value. We enrolled 53 patients diagnosed with WHO G2/G3 brain gliomas treated between 2012-2016. RT-qPCR based expression of miR-200 family was assessed in tumor and surrounding non-cancerous tissue. An analysis of selected clinico-pathological features was carried out. A logistic regression model was prepared for the miRNA signature. The predictive potential of the signature was assessed using the ROC curve. A stepwise backward regression model was used to select variables with a significant predictive potential related to OS. It was shown that miR-200a-3p, miR-200a-5p, miR-200c-5p, miR-141-3p and miR-429 can be independent predictors of survival. Better 2- and 5-year OS was associated with higher expression of miR-200a-3p, miR141-3p and lower expression of miR-200a-5p, miR-200c-5p, miR-429. The strongest predictors of survival were miR-200a-5p, miR-200b-3p, miR-200c-5p, miR-141-3p, miR-429, tumor volume and CTV. Members of the miR-200 family exhibit prognostic value for 2- and 5-year OS. Presented predictive models of survival may be clinically useful for treatment optimization.

The Systemic Inflammation Response Index Efficiently Discriminates between the Failure Patterns of Patients with Isocitrate Dehydrogenase Wild-Type Glioblastoma Following Radiochemotherapy with FLAIR-Based Gross Tumor Volume Delineation

BACKGROUND/OBJECTIVES

The objective of this study was to assess the connection between the systemic inflammation response index (SIRI) values and failure patterns of patients with IDH wild-type glioblastoma (GB) who underwent radiotherapy (RT) with FLAIR-based gross tumor volume (GTV) delineation.

METHODS

Seventy-one patients who received RT at a dose of 60 Gy to the GTV and 50 Gy to the clinical target volume (CTV) and had documented recurrence were retrospectively analyzed. Each patient's maximum distance of recurrence (MDR) from the GTV was documented in whichever plane it extended the farthest. The failure patterns were described as intra-GTV, in-CTV/out-GTV, distant, and intra-GTV and distant. For analytical purposes, the failure pattern was categorized into two groups, namely Group 1, intra-GTV or in-CTV/out-GTV, and Group 2, distant or intra-GTV and distant. The SIRI was calculated before surgery and corticosteroid administration. A receiver operating characteristic (ROC) curve analysis was used to determine the optimal SIRI cut-off that distinguishes between the different failure patterns.

RESULTS

Failure occurred as follows: intra-GTV in 40 (56.3%), in-CTV/out-GTV in 4 (5.6%), distant in 18 (25.4%), and intra-GTV + distant in 9 (12.7%) patients. The mean MDR was 13.5 mm, and recurrent lesions extended beyond 15 mm in only seven patients. Patients with an SIRI score ≥ 3 demonstrated a significantly higher incidence of Group 1 failure patterns than their counterparts with an SIRI score < 3 (74.3% vs. 50.0%; p = 0.035).

CONCLUSIONS

The present results show that using the SIRI with a cut-off value of ≥3 significantly predicts failure patterns. Additionally, the margin for the GTV can be safely reduced to 15 mm when using FLAIR-based target delineation in patients with GB.

Comparison of different target volume delineation strategies based on recurrence patterns in adjuvant radiotherapy for glioblastoma

Background

Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC) recommendations are commonly used guidelines for adjuvant radiotherapy in glioblastoma. In our institutional protocol, we delineate T2-FLAIR alterations as gross target volume (GTV) with reduced clinical target volume (CTV) margins. We aimed to present our oncologic outcomes and compare the recurrence patterns and planning parameters with EORTC and RTOG delineation strategies.

Methods

Eighty-one patients who received CRT between 2014 and 2021 were evaluated retrospectively. EORTC and RTOG delineations performed on the simulation computed tomography and recurrence patterns and planning parameters were compared between delineation strategies. Statistical Package for the Social Sciences (SPSS) version 23.0 (IBM, Armonk, NY, USA) was utilized for statistical analyses.

Results

Median overall survival and progression-free survival were 21 months and 11 months, respectively. At a median 18 month follow-up, of the 48 patients for whom recurrence pattern analysis was performed, recurrence was encompassed by only our institutional protocol's CTV in 13 (27%) of them. For the remaining 35 (73%) patients, recurrence was encompassed by all separate CTVs. In addition to the 100% rate of in-field recurrence, the smallest CTV and lower OAR doses were obtained by our protocol.

Conclusions

The current study provides promising results for including the T2-FLAIR alterations to the GTV with smaller CTV margins with impressive survival outcomes without any marginal recurrence. The fact that our protocol did not result in larger irradiated brain volume is further encouraging in terms of toxicity.

Impact of clinical target volume margin reduction in glioblastoma patients treated with concurrent chemoradiation

Background

Glioblastoma (GBM) is widely treated using large radiotherapy margins, resulting in substantial irradiation of the surrounding cerebral structures. In this context, the question arises whether these margins could be safely reduced. In 2018, clinical target volume (CTV) expansion was reduced in our institution from 20 to 15 mm around the gross target volume (GTV) (ie, the contrast-enhancing tumor/cavity). We sought to retrospectively analyze the impact of this reduction.

Methods

All adult patients with GBM treated between January 2015 and December 2020 with concurrent chemoradiation (60Gy/2Gy or 59.4Gy/1.8Gy) were analyzed. Patients treated using a 20 (CTV20, n = 57) or 15 mm (CTV15, n = 56) CTV margin were compared for target volumes, dose parameters to the surrounding organs, pattern of recurrence, and survival outcome.

Results

Mean GTV was similar in both groups (ie, CTV20: 39.7cm3; CTV15: 37.8cm3; P = .71). Mean CTV and PTV were reduced from 238.9cm3 to 176.7cm3 (P = .001) and from 292.6cm3 to 217.0cm3 (P < .001), for CTV20 and CTV15, respectively. As a result, average brain mean dose (Dmean) was reduced from 25.2Gy to 21.0Gy (P = .002). Significantly lower values were also observed for left hippocampus Dmean, brainstem D0.03cc, cochleas Dmean, and pituitary Dmean. Pattern of recurrence was similar, as well as patient outcome, ie, median progression-free survival was 8.0 and 7.0 months (P = .80), and median overall survival was 11.0 and 14.0 months (P = .61) for CTV20 and CTV15, respectively.

Conclusions

In GBM patients treated with chemoradiation, reducing the CTV margin from 20 to 15 mm appears to be safe and offers the potential for less treatment toxicity.

Dosimetric patterns of failure in the era of novel chemoradiotherapy in newly-diagnosed glioblastoma patients

BACKGROUND

Patterns of failure (POF) may provide an alternative quantitative endpoint to overall survival for evaluation of novel chemoradiotherapy regimens with glioblastoma.

MATERIALS AND METHODS

POF of 109 newly-diagnosed glioblastoma patients per 2016 WHO classification who received conformal radiotherapy with concomitant and adjuvant temozolomide were reviewed. Seventy-five of those patients also received an investigational chemotherapy agent (everolimus, erlotinib, or vorinostat). Recurrence volumes were defined with MRI contrast enhancement. POF at protocol (POFp), initial (POFi), and RANO (POFRANO) progression timepoints were characterized by the percentage of recurrence volume within the 95% dose region. POFp, POFi, and POFRANO of each patient were categorized (central, non-central, or both).

RESULTS

POF of the temozolomide-only control cohort were unchanged (79% central, 12% non-central, and 9% both) across protocol, initial, and RANO progression timepoints. Unlike the temozolomide-only cohort, POF of the collective novel chemotherapy cohort appeared increasingly non-central when comparing POFi with POFp, with a non-central component increasing from 16% to 29% (p = 0.078). POF did not correlate with overall survival or time to progression.

CONCLUSION

POF of patients receiving a novel chemotherapy appeared to be influenced by the timepoint of analysis and were increasingly non-central at protocol progression as compared with initial recurrence, suggesting that recurrence originates from the central region. Addition of everolimus and vorinostat appeared to influence POF, despite similar survival outcomes with the temozolomide-only control group. In studies dealing with novel therapeutic agents, robust and properly-timed dosimetric POF analysis may be helpful to evaluate biologic aspects of novel agents.

ESTRO-EANO guideline on target delineation and radiotherapy details for glioblastoma

BACKGROUND AND PURPOSE

Target delineation in glioblastoma is still a matter of extensive research and debate. This guideline aims to update the existing joint European consensus on delineation of the clinical target volume (CTV) in adult glioblastoma patients.

MATERIAL AND METHODS

The ESTRO Guidelines Committee identified 14 European experts in close interaction with the ESTRO clinical committee and EANO who discussed and analysed the body of evidence concerning contemporary glioblastoma target delineation, then took part in a two-step modified Delphi process to address open questions.

RESULTS

Several key issues were identified and are discussed including i) pre-treatment steps and immobilisation, ii) target delineation and the use of standard and novel imaging techniques, and iii) technical aspects of treatment including planning techniques and fractionation. Based on the EORTC recommendation focusing on the resection cavity and residual enhancing regions on T1-sequences with the addition of a reduced 15 mm margin, special situations are presented with corresponding potential adaptations depending on the specific clinical situation.

CONCLUSIONS

The EORTC consensus recommends a single clinical target volume definition based on postoperative contrast-enhanced T1 abnormalities, using isotropic margins without the need to cone down. A PTV margin based on the individual mask system and IGRT procedures available is advised; this should usually be no greater than 3 mm when using IGRT.

Location of Recurrences after Trimodality Treatment for Glioblastoma with Respect to the Delivered Radiation Dose Distribution and Its Influence on Prognosis

BACKGROUND

While prognosis of glioblastoma after trimodality treatment is well examined, recurrence pattern with respect to the delivered dose distribution is less well described. Therefore, here we examine the gain of additional margins around the resection cavity and gross-residual-tumor.

METHODS

All recurrent glioblastomas initially treated with radiochemotherapy after neurosurgery were included. The percentage overlap of the recurrence with the gross tumor volume (GTV) expanded by varying margins (10 mm to 20 mm) and with the 95% and 90% isodose was measured. Competing-risks analysis was performed in dependence on recurrence pattern.

RESULTS

Expanding the margins from 10 mm to 15 mm, to 20 mm, to the 95%- and 90% isodose of the delivered dose distribution with a median margin of 27 mm did moderately increase the proportion of relative in-field recurrence volume from 64% to 68%, 70%, 88% and 88% (p < 0.0001). Overall survival of patients with in-and out-field recurrence was similar (p = 0.7053). The only prognostic factor significantly associated with out-field recurrence was multifocality of recurrence (p = 0.0037). Cumulative incidences of in-field recurrences at 24 months were 60%, 22% and 11% for recurrences located within a 10 mm margin, outside a 10 mm margin but within the 95% isodose, or outside the 95% isodose (p < 0.0001). Survival from recurrence was improved after complete resection (p = 0.0069). Integrating these data into a concurrent-risk model shows that extending margins beyond 10 mm has only small effects on survival hardly detectable by clinical trials.

CONCLUSIONS

Two-thirds of recurrences were observed within a 10 mm margin around the GTV. Smaller margins reduce normal brain radiation exposure allowing for more extensive salvage radiation therapy options in case of recurrence. Prospective trials using margins smaller than 20 mm around the GTV are warranted.

Feasibility of clinical target volume reduction for glioblastoma treated with standard chemoradiation based on patterns of failure analysis

PURPOSE

To analyze recurrence patterns in patients with glioblastoma (GBM) after standard chemoradiation according to different target volume delineation strategies.

METHODS AND MATERIALS

Two hundred seven patients with GBM who recurred after standard chemoradiation were evaluated. According to ESTRO target volume delineation guideline, the CTV was generated by adding a 2-cm margin to the GTV, defined as the resection cavity plus residual tumor. Patterns of failure were analyzed using dose-volume histogram. Recurrent lesions were defined as in-field, marginal, or distant if > 80 %, 20-80 %, or < 20 % of the intersecting volume was included in the 95 % isodose line.For each patient, a theoretical plan consisting of reduced 1-cm GTV-to-CTV margin was created to compare patterns of failure and radiation doses to normal brain.

RESULTS

Median overall survival and progression-free survival times were 15.3 months and 7.8 months, respectively, from the date of surgery. Recurrences were in-field in 180, marginal in 5, and distant in 22 patients. According to MGMT promoter methylation, distant recurrences occurred in 18.6 % of methylated and 6 % of unmethylated tumors (p = 0.0046). Following replanning with 1-cm reduced margin, dosimetric analysis showed similar patterns of failure. Recurrences were in-field, marginal, and distant in 177, 3, and 27 plans, respectively, although radiation doses to the healthy brain and hippocampi were significantly lower compared with standard target delineation (p = 0.0001).

CONCLUSION

Current provide the rationale for evaluating GTV-to-CTV margin reduction in future clinical trials with the aim of limiting the cognitive sequelae of GBM irradiation while maintaining survival benefits of standard chemoradiation.

Optimization of brain tumours irradiation determining the set-up margin

The aim of this work was to evaluate whether the excising margin of the clinical tumor volume and planning target volume correspond with calculated radiation margin based on systematic errors, and definition of radiation margins of individual brain lobes. This research was a retrospective cross-sectional study. We checked the systematic errors and calculated their average and the size of radiation margins. The average systematic errors were calculated in four directions: lateral, longitudinal, vertical, and rotation. The largest average systematic error was calculated in the lateral direction in the cerebellar area, and the error was also statistically significant(p < 0.05). In rotational direction we notice the statistically significant difference in frontal lopbe (p = 0.037), and cerebellar area (p = 0.002). The largest safety margin, as measured by the apverage systematic errors, is requirped for irradiation of the cerebellum. The safety margin size of 6.94 mm was calculated according to the formula of Van Herk. However, the smallest safety margin can be used for irradiation of the occipital lobe of the brain, namely 4.85 mm. The linear regression results that only cerebellar lesions affect lateral displacements. Based on our calculation of the mean systematic errors, we estimate that the clinical target volume - planning target volume safety margin can't be reduced further from the current 5 mm to a size of 3 mm without the use of image guided radiotherapy.

Does the dural resection bed need to be irradiated? Patterns of recurrence and implications for postoperative radiotherapy for temporal lobe gliomas

Background

Patterns of recurrence and survival with different surgical and radiotherapy (RT) techniques were evaluated to guide RT target volumes for patients with temporal lobe glioma.

Methods and Materials

This retrospective cohort study included patients with World Health Organization grades II to IV temporal lobe glioma treated with either partial (PTL) or complete temporal lobectomy (CTL) followed by RT covering both the parenchymal and dural resection bed (whole-cavity radiotherapy [WCRT]) or the parenchymal resection bed only (partial-cavity radiotherapy [PCRT]). Patterns of recurrence, progression-free survival (PFS) and overall survival (OS) were evaluated.

Results

Fifty-one patients were included and 84.3% of patients had high-grade glioma (HGG). CTL and PTL were performed for 11 (21.6%) and 40 (78.4%) patients, respectively. Median RT dose was 60 Gy (range, 40-76 Gy). There were 82.4% and 17.6% of patients who received WCRT and PCRT, respectively. Median follow-up time was 18.4 months (range, 4-161 months). Forty-six patients (90.2%) experienced disease recurrence, most commonly at the parenchymal resection bed (76.5%). No patients experienced an isolated dural recurrence. The median PFS and OS for the PCRT and WCRT cohorts were 8.6 vs 10.8 months (P = .979) and 19.9 vs 18.6 months (P = .859), respectively. PCRT was associated with a lower RT dose to the brainstem, optic, and ocular structures, hippocampus, and pituitary.

Conclusion

We identified no isolated dural recurrence and similar PFS and OS regardless of postoperative RT volume, whereas PCRT was associated with dose reduction to critical structures. Omission of dural RT may be considered a reasonable alternative approach. Further validation with larger comparative studies is warranted.

Feasibility of hippocampus-sparing VMAT for newly diagnosed glioblastoma treated by chemoradiation: pattern of failure analysis

Background

To identify the pattern of failure and oncological safety of hippocampus (HC)-sparing IMRT (HSRT) in newly diagnosed glioblastoma (GBM) patients.

Materials and methods

Eighty-two GBM patients treated with temozolomide-based chemoradiation using HSRT between 2014 and 2018 were retrospectively reviewed. HSRT consisted of a sparing of D_max of the contralateral HC < 17 Gy. Fifteen patients were unable to achieve the dose-constraints for adequate target coverage. The dose to ipsilateral HC was kept as low as possible. The pattern of failure was investigated, focusing on the area in the vicinity of the spared HC (organ and + 1 cm area). The median HSRT dose was 60 Gy in 30 fractions.

Results

The median follow-up for survivors was 11.7 months. The median progression-free and overall survival were 9.7 and 23.5 months, respectively. Six (7.3%) and eight (9.8%) patients eventually demonstrated progressive disease at the contralateral HC and HC + 1 cm, respectively. The 12-month contralateral HC and HC + 1 cm failure-free rate were 97.2 and 93.4%, respectively. However, no patient (0%) and two patients (2.4%) showed failure at contralateral HC and HC + 1 cm at initial progression, respectively. The dominant pattern of failure at the contralateral HC was by subependymal seeding (66.7%).

Conclusion

The incidence of failure at the contralateral HC and HC + 1 cm is very low and mostly accompanied by disseminated disease progression after HSRT. Since HSRT does not compromise oncological outcomes, it could be considered especially for GBM patients who are expected to have favorable survival outcomes.

NRG brain tumor specialists consensus guidelines for glioblastoma contouring

INTRODUCTION

NRG protocols for glioblastoma allow for clinical target volume (CTV) reductions at natural barriers; however, literature examining CTV contouring and the relevant white matter pathways is lacking. This study proposes consensus CTV guidelines, with a focus on areas of controversy while highlighting common errors in glioblastoma target delineation.

METHODS

Ten academic radiation oncologists specializing in brain tumor treatment contoured CTVs on four glioblastoma cases. CTV expansions were based on NRG trial guidelines. Contour consensus was assessed and summarized by kappa statistics. A meeting was held to discuss the mathematically averaged contours and form consensus contours and recommendations.

RESULTS

Contours of the cavity plus enhancement (mean kappa 0.69) and T2-FLAIR signal (mean kappa 0.74) showed moderate to substantial agreement. Experts were asked to trim off anatomic barriers while respecting pathways of spread to develop their CTVs. Submitted CTV_4600 (mean kappa 0.80) and CTV_6000 (mean kappa 0.81) contours showed substantial to near perfect agreement. Simultaneous truth and performance level estimation (STAPLE) contours were then reviewed and modified by group consensus. Anatomic trimming reduced the amount of total brain tissue planned for radiation targeting by a 13.6% (range 8.7-17.9%) mean proportional reduction. Areas for close scrutiny of target delineation were described, with accompanying recommendations.

CONCLUSIONS

Consensus contouring guidelines were established based on expert contours. Careful delineation of anatomic pathways and barriers to spread can spare radiation to uninvolved tissue without compromising target coverage. Further study is necessary to accurately define optimal target volumes beyond isometric expansion techniques for individual patients.