Radiation dose-volume effects in the brain

Does Time to Retreatment Matter? A Normal Tissue Complication Probability Model to Predict Radionecrosis After Repeat Stereotactic Radiosurgery for Recurrent Brain Metastases Incorporating Time-dependent Discounted Dose

PURPOSE

To develop and compare normal tissue complication probability (NTCP) models for recurrent brain metastases (BMs) treated with repeat single-fraction stereotactic radiosurgery (SRS), considering time-dependent discounted prior dose.

METHODS AND MATERIALS

We developed three NTCP models (M0, M1-retreat, and M1-combo models) of BMs treated with GammaKnife-based SRS. The maximum dose is 0.2 cc (D0.2cc) of the lesion-specific brain, and the 1-year radionecrosis risk is modeled using a logistic response with doses converted into equivalent dose in 2-Gy fractions (EQD2) based on a linear quadratic linear model. The M0 and M1-retreat models, respectively, predicted radionecrosis risk after SRS to 1029 nonrecurrent lesions (patients, 262) and second SRS to 149 recurrent lesions (patients, 87). The M1-combo model accounted for the second SRS and time-dependent discounted first SRS dose for recurrent lesions estimated using a modified Gompertzian function.

RESULTS

All 3 models fitted the data well (χ2, 0.039-0.089, and P = 0.999-1.000). The fitted EQD250 was ∼ 103 Gy for the M0 model, ∼ 88 Gy for the M1-retreat model, and ∼ 165 Gy for the M1-combo model. The fitted γ50 exhibited a progressively flatter dose-response curve across the three models, with values of 1.2 per gray for the M0 model, 0.6 per gray for the M1-retreat model, and 0.4 per gray for the M1-combo model. For the brain D0.2cc of 29 and 19 Gy, the steepest to shallowest dose-response or largest change in NTCP values, ie, NTCP29Gy - NTCP19Gy, was observed in the M1-retreat (0.16), M0 (0.14), and M1-combo (0.06) models.

CONCLUSIONS

The model-fitted parameters predicted that recurrent BMs would have a lower threshold dose tolerance and a more gradual dose response to the second SRS than nonrecurrent BMs. This gradual dose-response becomes even more apparent when considering the time-dependent discounted first SRS as a cumulative second SRS. Tailoring SRS retreatment protocols based on NTCP modeling can potentially enhance therapeutic efficacy.

Gross tumor volume increase and need for adaptive radiotherapy in pediatric-type diffuse high-grade glioma of the midline structures

INTRODUCTION

Current pediatric-type diffuse high-grade glioma radiotherapy protocols apply a 1.0 cm clinical target volume (CTV) margin around the gross tumor volume (GTV). However, in adults with glioblastoma, large variations in GTV are observed during radiotherapy. The study aimed to map the GTV variation during a 6-week course of radiotherapy using repeated MR-imaging and to evaluate the need for plan adaptation. Also, the relation between GTV increase and time to disease progression (TTP) was assessed.

MATERIAL AND METHODS

Patients with newly diagnosed diffuse midline glioma or diffuse pediatric-type high-grade glioma of the midline structures undergoing a 6-week radiotherapy course, were eligible for inclusion. MRI scans were performed in the pre-treatment phase (MRI0), and at fraction 10 + 20 (rMRI10/rMRI20). On all scans, GTV was delineated. An increase was defined as a >5 % increase of GTV between scans. The need for treatment plan adaptation was based on dosimetric and visual criteria. GTV increase was compared to TTP.

RESULTS

Twenty patients were eligible. In 12/20 patients, a GTV increase was observed at rMR10/rMR20, more specifically in 6/11 pontine and 6/9 non-pontine tumors. Combining dosimetric criteria and visual inspection, 20 plan adaptations in 14 patients were required. The TTP (range: 1.6-17.6 months) was not significantly different between the group with (median 8.1 months) versus without a GTV increase (median 7.6 months; p = 0.66).

CONCLUSION

Repeated imaging demonstrated a GTV increase in 60 % of patients and plan adaptation in 70 %. When applying CTV margins of 1.0 cm, plan adaptation is recommended to ensure adequate radiotherapy treatment.

Advancing glioblastoma therapy: Learning from the past and innovations for the future

Marred by a median survival of only around 12-15 months coupled with poor prognosis and effective therapeutic deprived drug armory, treatment/management of glioblastoma has proved to be a daunting task. Surgical resection, flanked by radiotherapy and chemotherapy with temozolomide, stands as the standard of care; however, this trimodal therapy often manifests limited efficacy due to the heterogeneous and highly infiltrative nature of GBM cells. In addition, the existence of the blood-brain barrier, tumor microenvironment, and the immunosuppressive nature of GBM, along with the encountered resistance of GBM cells towards conventional therapy, also hinders the therapeutic applications of chemotherapeutics in GBM. This review presents key insights into the molecular pathology of GBM, including genetic mutations, signaling pathways, and tumor microenvironment characteristics. Recent innovations such as immunotherapy, oncolytic viral therapies, vaccines, nanotechnology, electric field, and cancer neuroscience, as well as their clinical progress, have been covered. In addition, this compilation also encompasses a discussion on the role of personalized medicine in tailoring treatments based on individual tumor profiles, an approach that is gradually shifting the paradigm in GBM management. Endowed with the learnings imbibed from past failures coupled with the zeal to embrace novel/multidisciplinary approaches, researchers appear to be on the right track to pinpoint more effective and durable solutions in the context of GBM treatment.

Left hippocampus sparing model for glioblastoma radiotherapy by utilizing knowledge-based planning and multi-criteria optimization

PURPOSE

Results of a prospective, randomized controlled trial at our institute demonstrate an association between the dose to the left hippocampus and neurocognitive decline post-radiotherapy for patients with glioblastoma. To minimize the dose to the left hippocampus, a left hippocampus sparing model was created using RapidPlan (RP) and multi-criteria optimization (MCO).

MATERIALS AND METHODS

For 147 patients with newly diagnosed glioblastoma treated with volumetric modulated arc therapy (VMAT), the left and right hippocampus were delineated. Ninety-seven of 147 VMAT plans were used to configure a RP model named HCS1. The remaining 50 VMAT plans were used for the model validation. All 97 plans were replanned with the HCS1 and further optimized using MCO (HCS1+MCO). MCO was used to explore the trade-off between reducing the left hippocampus mean dose and planning objectives for the targets and other organs-at-risk (OAR) for HCS1 plans. These plans were used to create a new model called HCS2. MCO and RP model configuration were done within the Eclipse treatment planning system.

RESULTS

The final HCS2 model decreased the mean dose to the left hippocampus by 26% compared to clinically treated plans without reducing target coverage for 50 validation data. The mean dose to the left hippocampus decreased from 32.65 Gy in clinically treated plans, 30.45 Gy in HCS1-generated plans, and 24.04 Gy in HCS2-generated plans. The mean volume receiving 95% of the prescription dose (V95%) of the planning target volume was 99.08% ± 1.39% in clinically treated plans, 99.03% ± 1.37% in HCS1-generated plans, and 98.80% ± 1.48% in HCS2-generated plans. Mean dose to 0.1 cc of the brainstem improved from 45.91 Gy in clinically treated plans to 39.29 Gy in HCS2-generated plans.

CONCLUSIONS

The RP model and MCO helps to decrease left hippocampus mean dose while maintaining the target volume coverage and OAR sparing comparable to clinically treated plans for glioblastoma patients.

The impact of pituitary adenomas on cognitive performance: a systematic review

Purpose

Increasing evidence suggests that beyond classical endocrine and visual symptoms, patients with pituitary adenoma (PA) may experience neurocognitive impairment, potentially resulting in reduced productivity and diminished quality of life. Prior studies have used diverse cognitive assessment tools across heterogeneous populations, leading to inconsistent findings. To address the variability, our study systematically analyzes the assessment batteries used in previous research, clarifying their corresponding cognitive domains. We seek to provide a more consistent and comprehensive understanding of the neurocognitive implications associated with PAs.

Methods

This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses reporting guideline. Individual patient-level data, including clinical characteristics, tumor subtype, treatment interventions, hormonal status, and psychological outcomes, were systematically collected. Cognitive assessment tools were categorized according to their corresponding cognitive domains to facilitate domain-specific analyses.

Results

This systematic review included 70 studies encompassing a total of 3,842 patients with PA. Of these, 60 studies employed either objective neuropsychological tests or subjective questionnaires to evaluate cognitive function. The most frequently utilized assessment was the Digit Span test, with 42.9% of studies reporting significant impairments in complex attention and executive functioning among patients with PA. Twelve studies focused on structural brain changes as assessed by magnetic resonance imaging, with half documenting volumetric reductions in gray matter. Across the various PA subtypes, a consistent decline in discrete cognitive domains was observed, most notably in memory and executive function. Treatment-related data were provided in 59 studies. Perioperative changes in cognitive performance were described in 14 studies, of which 11 reported post-surgical improvement in at least one cognitive domain. Twenty studies investigated the potential adverse effects of radiotherapy on cognitive function; among them, 16 found no significant differences following treatment. Eight studies examined the association between tumor size and cognitive impairment; seven reported no statistically significant correlation. In contrast, 24 studies identified a significant relationship between hormonal dysregulation and cognitive decline.

Conclusions

The literature contains heterogeneous findings about the cognitive performance, nature of cognitive impairment, and subsequent effects of treatment. Patients with PA may experience cognitive decline in specific areas and are notably affected by hormone levels, while treatment may lead to cognitive recovery. The proposed tiered cognitive evaluation approach can improve assessment consistency in future practice.

Stereotactic and fractionated stereotactic radiosurgery for single and multiple brain metastases: Results of multicenter planning studies

PURPOSE

Stereotactic and fractionated stereotactic radiosurgery (SRS/fSRS) utilization is growing in India, although planning studies are scarce. This study assessed clinical practices for SRS/fSRS treatment planning for brain metastases (BM) using ICRU-91 and explored the impact of planning tools.

METHODS & MATERIALS

Participants from 23 centers received two anonymized CT datasets with predrawn structures for single met (SM) and four BMs (MM) cases via email. Centers used local protocol to create plans. The plans were evaluated for target coverage, normal brain doses, and ICRU-91 dosimetric indices.

RESULTS

Monaco TPS overestimated mean GTV (PTV) by 3.7 (4.2)% and 2.1 (2.0)% for SM and MM respectively. Some institutions had good conformity and target coverage, whereas others had high OAR doses despite inadequate PTV dose coverage. Conformity index (CI) ranged from 1.07 to 1.45 (SM) and 1.06 to 1.25 (MM), and homogeneity index (HI) ranged from 0.07 to 0.28 (SM) and 0.13 to 0.32 (MM). Significant variation in GI and dose prescription isodose line selection was observed among centers.

CONCLUSIONS

There was a significant heterogeneity in the planning parameters noted among different centers. The study emphasized the importance of established planning protocols and comprehensive training for staff involved in SRS/fSRS. Notably, plans with finer MLC width outperformed, yet wider MLC plans achieved ICRU-91 indices comparable to published literature. The importance of our study is underscored by the absence of a national framework for SRS planning in India.

Total brain dose estimation in single-isocenter-multiple-targets (SIMT) radiosurgery via a novel deep neural network with spherical convolutions

BACKGROUND AND PURPOSE

Accurate prediction of normal brain dosimetric parameters is crucial for the quality control of single-isocenter multi-target (SIMT) stereotactic radiosurgery (SRS) treatment planning. Reliable dose estimation of normal brain tissue is one of the great indicators to evaluate plan quality and is used as a reference in clinics to improve potentially SIMT SRS treatment planning quality consistency. This study aimed to develop a spherical coordinate-defined deep learning model to predict the dose to a normal brain for SIMT SRS treatment planning.

METHODS

By encapsulating the human brain within a sphere, 3D volumetric data of planning target volume (PTVs) can be projected onto this geometry as a 2D spherical representation (in azimuthal and polar angles). A novel deep learning model spherical convolutional neural network (SCNN) was developed based on spherical convolution to predict brain dosimetric evaluators from spherical representation. Utilizing 106 SIMT cases, the model was trained to predict brain V50%, V60%, and V66.7%, corresponding to V10Gy and V12Gy, as key dosimetric indicators. The model prediction performance was evaluated using the coefficient of determination (R2), mean absolute error (MAE), and mean absolute percentage error (MAPE).

RESULTS

The SCNN accurately predicted normal brain dosimetric values from the modeled spherical PTV representation, with R2 scores of 0.92 ± 0.05/0.94 ± 0.10/0.93 ± 0.09 for V50%/V60%/V66.7%, respectively. MAEs values were 1.94 ± 1.61 cc/1.23 ± 0.98 cc/1.13 ± 0.99 cc, and MAPEs were 19.79 ± 20.36%/20.79 ± 21.07%/21.15 ± 22.24%, respectively.

CONCLUSIONS

The deep learning model provides treatment planners with accurate prediction of dose to normal brain, enabling improved consistency in treatment planning quality. This method can be extended to other brain-related analyses as an efficient data dimension reduction method.

Dosimetric and radiobiological evaluation of stereotactic radiosurgery using volumetric modulated arc therapy and dynamic conformal arc therapy for multiple brain metastases

This paper presents a clinical comparison of the target dose, normal tissue complication probability (NTCP), and plan quality between volumetric modulated conformal arc therapy (VMAT) against dynamic conformal arc therapy (DCAT) techniques to facilitate clinical decision-making in multiple brain metastases (MBM) treatment. A total of 11 cases having 33 lesions were recruited at the Union Oncology Centre, Union Hospital, Hong Kong SAR. With CT images available, all plans were optimized using both HyperArc (HA) and Brainlab Elements Multiple Brain Metastases (Elements MBM). Target coverage, normal tissue sparing, and dose distribution were compared pairwise between VMAT and DCAT. Results showed that the plans generated using both techniques achieved adequate target coverage to meet up with the oncologist's prescription. With similar levels of NTCP, the normal brain received low doses of radiation using both techniques and the risk of brain necrosis was kept equally low. This indicated that VMAT and DCAT produced similar high-quality treatment plans with low risks of brain necrosis. Meanwhile, VMAT showed better homogeneity which could potentially be more useful for large targets, while DCAT showed better target conformity especially for targets smaller than 1 cc. In general, both HA and Elements MBM demonstrated ability to generate high-quality clinical plans.

Intra-Arterial Super-Selective Delivery of Yttrium-90 for the Treatment of Recurrent Glioblastoma: In Silico Proof of Concept with Feasibility and Safety Analysis

Background: Intra-arterial cerebral infusion (IACI) of radiotherapeutics is a promising treatment for glioblastoma (GBM) recurrence. We investigated the in silico feasibility and safety of Yttrium-90-Poly(vinyl alcohol)-Microbubble (90Y-PVA-MB) IACI in patients with recurrent GBM and compared the results with those of external beam radiation therapy (EBRT). Methods: Contrast-enhanced T1-weighted magnetic resonance imaging (T1W-MRI) was used to delineate the tumor volumes and CT scans were used to automatically segment the organs at risk in nine patients with recurrent GBM. Volumetric Modulated Arc Therapy (VMAT) treatment plans were generated using a clinical treatment planning system. Assuming the relative intensity of each voxel from the MR-T1W as a valid surrogate for the post-IACI 90Y-PVA-MB distribution, a specific 90Y dose voxel kernel was obtained through Monte Carlo (MC) simulations and convolved with the MRI, resulting in a 90Y-PVA-MB-based dose distribution that was then compared with the VMAT plans. Results: The physical dose distribution obtained from the simulation of 1GBq of 90Y-PVA-MBs was rescaled to ensure that 95% of the prescribed dose was delivered to 95% or 99% of the target (i.e., A95% and A99%, respectively). The calculated activities were A95% = 269.2 [63.6-2334.1] MBq and A99% = 370.6 [93.8-3315.2] MBq, while the mean doses to the target were 58.2 [58.0-60.0] Gy for VMAT, and 123.1 [106.9-153.9] Gy and 170.1 [145.9-223.8] Gy for A95% and A99%, respectively. Additionally, non-target brain tissue was spared in the 90Y-PVA-MB treatment compared to the VMAT approach, with a median [range] of mean doses of 12.5 [12.0-23.0] Gy for VMAT, and 0.6 [0.2-1.0] Gy and 0.9 [0.3-1.5] Gy for the 90Y treatments assuming A95% and A99%, respectively. Conclusions: 90Y-PVA-MB IACI using MR-T1W appears to be feasible and safe, as it enables the delivery of higher doses to tumors and lower doses to non-target volumes compared to the VMAT approach.

Pathological Mechanisms of Irradiation-Induced Neurological Deficits in the Developing Brain

Cranial irradiation or radiotherapy (CRT) is one of the essential therapeutic modalities for central nervous system (CNS) tumors, and its efficacy is well known. Nevertheless, CRT is also associated with brain damages such as focal cerebral necrosis, neuroinflammation, cerebral microvascular anomalies, neurocognitive dysfunction, and hormone deficiencies in children. Children's brains are much more sensitive to CRT compared to the adult's brains. Thus, children's brains are also more likely to develop long-term CRT complication, which severely lessens their long-term quality of life after treatment. CRT to the juvenile rat led to a retardation of growth of the cerebellum; both the gray and white matter and neurogenic regions like the subventricular zone and the dentate gyrus in the hippocampus were predominantly vulnerable to CRT. Also, CRT-induced cognitive changes typically manifested as deficits in hippocampal-related functions of learning as well as memory, such as spatial information processing. Fractionated CRT-stimulated cognitive decline and hormone deficiencies were precisely associated with augmented neuronal cell death, blockade of neurogenesis, and stimulation of astrocytes and microglia. Thus, the aim of this review is to highlight the pathological mechanism of CRT-induced neurological deficits in the developing brain.

Study Protocol of a Prospective Phase 2 Study of Chlorophyllin for the Management of Brain Radionecrosis in Patients With Diffuse Glioma (CHROME)

INTRODUCTION

Chlorophyllin (CHL) effectively decreases the side effects of radiotherapy (RT) by scavenging radiation-induced free radicals and reactive oxygen species in preclinical trials. This study aims to assess the efficacy of oral CHL for the treatment of brain radionecrosis in patients with diffuse glioma.

METHODS

This is a phase 2 trial prospective, interventional study. Adults (> 18 years) with a histological diagnosis of diffuse glioma developing radionecrosis will be eligible for the study. Radionecrosis will be identified using standard imaging protocols with magnetic resonance imaging (MRI) with or without positron emission tomography (PET). Patients will be accrued in two strata: symptomatic (stratum A) and asymptomatic (stratum B). Chlorophyllin will be prescribed to all patients using a morning oral dose of 750 mg before breakfast for 3 months. In addition, participants in stratum A will be given a tapering dose of dexamethasone for 1 month, while stratum B will not be receiving any steroids. Imaging with an MRI brain protocol and PET scan will be planned at 1 month and MRI at 3 months after starting CHL. The primary endpoint is the clinical-radiological response at 1 month. Secondary endpoints include response at 3 months, biological responses, survival analysis, and quality-of-life scores. The total sample size is 118 (60 and 58 in stratum A and B, respectively), with one interim analysis planned.

DISCUSSION

Radionecrosis leads to significant morbidity and is usually treated with corticosteroids, which can lead to several side effects from both acute and long-term use. Refractory radionecrosis requires treatment with bevacizumab or surgical resection. Chlorophyllin is a cheap, safe, and readily available phytopharmaceutical drug, which is being investigated in the phase 2 study and, if proven effective, can be considered an alternative for treating radionecrosis.

TRIAL REGISTRATION

Clinical Trial Registry India (CTRI): CTRI/2023/08/056166; ClinicalTrials.gov: NCT06016452.

Case report: A rare case of a long-term survivor of glioblastoma who underwent two courses of hypofractionated radiotherapy as part of her care

Glioblastoma (GB) is a primary brain tumor that is lethal and challenging to treat. The 3-year overall survival (OS) of patients with this diagnosis has stayed the same since 2005. The patient is a 75-year-old woman who presented with progressive aphasia and was diagnosed with GB (WHO grade 4, IDH1/IDH2 wild type, ATRX intact, p53 and PTEN mutant, BRAF non-mutated, O6-methylguanine-DNA methyltransferase promoter methylated) and who underwent surgical resection, hypofractionated radiotherapy (HFRT) using intensity-modulated radiotherapy (IMRT) (4,005 cGy in 15 fractions) alone, and adjuvant temozolomide (TMZ). She was progression-free for approximately 20 months. Although planned, concurrent TMZ was not used during the complete first course of HFRT due to the patient's performance status. After recurrence, another HFRT (35 Gy in 10 fractions) was employed. She was progression-free on imaging for 8 months until a recent follow-up scan showed potential progression versus radiation-related change. At the time of this case report, her care is still ongoing. This represents a rare case of a long-term survivor of GB who has received two courses of HFRT, a treatment option that is usually used in those with predicted shorter survival times.

Real-time dose measurement in minibeam radiotherapy using radioluminescence imaging

PURPOSE

Minibeam radiotherapy (MBRT) uses small parallel beams of radiation to create a highly modulated dose pattern. The aim of this study is to develop an optical radioluminescence imaging (RLI) approach to perform real-time dose measurement for MBRT.

METHODS

MBRT was delivered using an image-guided small animal irradiator equipped with a custom collimator. Five slabs of plastic scintillators with a thicknesses of 0.5, 1, 2, 3 and 10 mm were placed on top of a mouse phantom, to localize and measure the delivered dose. A thin radioluminescence film (Gd2O2S:Tb) was used to obtain the mini beam dose profile that was compared against GafChromic (GC) films measurements. The RLI signal was detected with a CMOS camera placed at 90 deg with respect to the beam axis. Monte Carlo (MC) simulations were also performed using TOPAS for comparison with the experimental results.

RESULTS

The measured peak to valley dose ratio (PVDR) obtained with RLI was 16.7 in line with GC films measurements. The differences between peak and valley dimension were less that 3% with respect to GC measurements. Using RLI performed with the scintillator slabs, it was possible to localize and measure in real-time MBRT delivery on the mouse phantom.

CONCLUSIONS

We proposed a novel method for MBRT dose localization and measurement in real-time based on RLI. The results we obtained are in good agreement with GC film measurements.

Optimising (re-)irradiation for locally recurrent head and neck cancer: impact of dose-escalation, salvage surgery, PEG tube and biomarkers on oncological outcomes-a single centre analysis

INTRODUCTION

Locoregional recurrence (LR) is common in locally advanced head and neck cancer (HNSCC), posing challenges for treatment. We analysed outcome parameters and toxicities for patients being treated with radiotherapy (RT) for LR-HNSCC and investigated patient and disease related prognostic factors in this prognostically unfavourable group.

METHODS

This analysis includes 101 LR-HNSCC patients treated with RT, radio-chemotherapy (RCT) or radio-immunotherapy (RIT) between 2010 and 2018 at a high-volume tertiary centre. Patient characteristics, tumour and treatment details were retrospectively collected. Overall survival (OS), progression-free survival (PFS) and toxicities according to Common Terminology Criteria for Adverse Events (CTCAE) v5.0 were assessed.

RESULTS

62% of patients were radiotherapy-naïve (initial RT group) while 38% were re-irradiated at site of LR (re-RT group). Median OS for initial RT was 24 months, for re-RT 12 months (p < 0.01). In the RCT subgroup, patients with initial RT had significantly longer OS with 35 months compared to re-RT 12 months (p < 0.05). Patients with UICC grade IV tumours and percutaneous endoscopic gastrostomy (PEG) tube had significantly shorter OS in multivariate analysis: initial RT 13 vs. re-RT 32 months and initial RT 12 vs. re-RT 32 months respectively. Salvage surgery before RT at recurrence was a positive prognostic factor for OS (initial RT 35 vs. re-RT 12 months). Other significant factors for longer OS in univariate analysis included low inflammatory status (Glasgow Prognostic Score 0) and radiation doses ≥ 50 Gy. We detected 37 (15%) ≥ CTCAE Grade 3 events for initial RT and 19 (15%) for re-RT patients.

CONCLUSION

In this analysis, we identified key prognostic factors including PEG tube and inflammation status that could guide treatment decision. Our findings suggest salvage surgery as preferred treatment option with postoperative RT at LR. Adverse events due to re-RT were acceptable. A radiation dose of ≥ 50 Gy should be administered to achieve better outcomes.

Fractionated reirradiation of recurrent high-grade gliomas: Safety with higher reirradiation dose and larger targets

Background

The optimal regimen, normal tissue tolerances, and appropriate indications for reirradiation for recurrent high-grade glioma (HGG) are uncertain. The aim of this study was to determine whether higher reirradiation dose was associated with toxicity or survival.

Methods

Patients with HGG treated with fractionated reirradiation at a single institution from 2007 to 2022 were retrospectively reviewed. Metrics evaluated included overall survival (OS), prognostic factors for survival, and treatment-related toxicity.

Results

Two hundred and thirty patients with recurrent HGG were reviewed. Median follow-up was 8.8 months. Median reirradiation dose was 41.4 Gy with 80.4% receiving concurrent systemic therapy. Median cumulative maximum doses to brainstem and optic structures were 77.9 Gy (range: 4.6-146.0 Gy) and 55.1 Gy (3.3-106.3 Gy), respectively. No injuries to these structures were identified. Radiation necrosis (RN) was identified in 9.4%. There were no significant associations between RN and target size, systemic therapy use, or reirradiation dose. Median OS was 10.2 months from reirradiation start. On multivariate analysis, improved OS was associated with better KPS, longer interval between radiotherapy sessions, reirradiation at first recurrence, and reirradiation dose ≥ 41.4 Gy. Median OS for those with IDH wildtype glioblastoma was 8.7 months. On multivariate analysis of an IDH wildtype disease subanalysis, improved OS was associated with longer interval between radiotherapy sessions and higher reirradiation dose.

Conclusions

These data support the safety and efficacy of fractionated reirradiation for recurrent HGG. They suggest higher reirradiation dose may be feasible, including for large treatment volumes and for tumors near the brainstem or optic structures.

Is Bevacizumab a Cost-Effective Regimen for Treating Cerebral Radiation Necrosis in the United States?

BACKGROUND

Bevacizumab has been demonstrated to have superior efficacy in the treatment of cerebral radiation necrosis (CRN), but its high cost may exacerbate the disease burden. This study aimed to assess the cost-effectiveness of bevacizumab in comparison to corticosteroids for treating CRN from the US payers' perspective.

METHODS

Decision tree models were constructed to simulate the process of bevacizumab and corticosteroids in CRN short-term and long-term therapy. Critical clinical data were derived from the NCT01621880 trial. Costs and utility values were obtained from the US official websites and published literature. The main outcomes were total costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER). One-way and probabilistic sensitivity analyses were performed to assess the robustness of the models.

RESULTS

In the short-term and long-term models, bevacizumab added 0.11 (0.46 vs 0.35) and 0.16 (0.54 vs 0.38) QALYs compared with corticosteroids therapy, with corresponding incremental costs of $12,351 and $23,253, respectively. The resultant ICERs were $112,987/QALY and $150,245/QALY for short-term and long-term treatment, respectively. The one-way sensitivity analysis indicated that utility value of nonrecurrence status, body weight, and bevacizumab price per cycle were the most influential factors for ICER of both models. At the willingness-to-pay threshold of $150,000/QALY in the United States, the probabilities of bevacizumab being cost-effective for CRN short and long-term treatment were 63.9% and 49%, respectively.

CONCLUSIONS

Compared with corticosteroids, bevacizumab is an economical alternative for CRN short-term treatment from the US payers' perspective, whereas long-term therapy draws an opposite conclusion.

Clinical Outcomes and Relevance of Composite V12 Gy in Patients With Four or More Brain Metastases Treated With Single Fraction Stereotactic Radiosurgery

AIMS

Tissue V12Gy (total brain volume receiving 12Gy including target) can predict for late toxicity in single target benign disease treated with stereotactic radiosurgery (SRS). The value of this metric remains uncertain for multiple brain metastases. This retrospective cohort study reports the outcomes and evaluates the predictors of toxicity in patients with four or more brain metastases treated with single-fraction SRS.

MATERIALS AND METHODS

Two hundred twenty-six patients with 2160 metastases treated from 2014-21 were retrospectively studied. Symptomatic late toxicity (new/progressive neurological symptoms ≥3 months post SRS) with magnetic resonance imaging (MRI) changes suggestive of treatment effect were analysed. Kaplan-Meier and competing risk analysis was used to assess survival and toxicity respectively.

RESULTS

median number of metastases/patient was 6 (range: 4-41) and median composite tissue V12Gy (inclusive of planning target volume (PTV)) was 11.3 cc (IQR: 6.1 cc-17.1 cc). Sixteen out of the 226 patients developed symptomatic late radiation adverse event (R-AE), and the cumulative incidence was 4.9% at 1 year and 6.9% at 2 years. The total target volume was significantly predictive of the risk of late R-AE. Volume of the largest lesion, V12Gy and V15Gy did not predict for late R-AE, but plotted graphs showed suggestions of linear relationships between dosimetric parameters and late R-AE.

CONCLUSION

Within the limitations of this study, the cumulative incidence of symptomatic toxicity remains acceptable despite routinely accepting a composite tissue V12Gy in excess of 10 cc to treat multiple brain metastases.

ADVANCES IN KNOWLEDGE

V12Gy has limitations as a plan quality metric in multiple brain metastases treated with SRS. There is insufficient evidence to have a defined target limit as <10 cc.

Radiation-Induced Brain Injury: Mechanistic Insights and the Promise of Gut-Brain Axis Therapies

Radiation therapy is widely recognized as an efficacious modality for treating neoplasms located within the craniofacial region. Nevertheless, this approach is not devoid of risks, predominantly concerning potential harm to the neural structures. Adverse effects may encompass focal cerebral necrosis, cognitive function compromise, cerebrovascular pathology, spinal cord injury, and detriment to the neural fibers constituting the brachial plexus. With increasing survival rates among oncology patients, evaluating post-treatment quality of life has become crucial in assessing the benefits of radiation therapy. Consequently, it is imperative to investigate therapeutic strategies to mitigate cerebral complications from radiation exposure. Current management of radiation-induced cerebral damage involves corticosteroids and bevacizumab, with preclinical research on antioxidants and thalidomide. Despite these efforts, an optimal treatment remains elusive. Recent studies suggest the gut microbiota's involvement in neurologic pathologies. This review aims to discuss the causes and existing treatments for radiation-induced cerebral injury and explore gut microbiota modulation as a potential therapeutic strategy.

Predicting radiotoxic effects after BNCT for brain cancer using a novel dose calculation model

PURPOSE

The normal brain is an important dose-limiting organ for brain cancer patients undergoing radiotherapy. This study aims to develop a model to calculate photon isoeffective doses (DIsoE) to normal brain that can explain the incidence of grade 2 or higher somnolence syndrome (SS⩾2) after Boron Neutron Capture Therapy (BNCT).

METHODS

A DIsoE model was constructed to find the reference photon dose that equals the Normal Tissue Complication Probability (NTCP) of the absorbed dose from BNCT. Limb paralysis rates from the rat spinal cord model exposed to conventional or BNCT irradiation were used to determine model parameters. NTCP expressions for both irradiations were constructed based on Lyman's model accordingly. DIsoE values were calculated for BNCT treatments performed in Finland and USA. An equivalent uniform dose (EUD) based on peak and average whole-brain doses and treatment fields was also introduced. Combining DIsoE and EUD models, a dose-response curve for SS⩾2 in BNCT patients was constructed and compared to conventional radiotherapy outcomes.

RESULTS

The DIsoE model reveals higher than expected photon-equivalent doses in the brain, indicating the need to modify standard dose calculation methods. Neither peak dose nor average whole-brain dose alone predicts SS⩾2 development. However, the dose-response curve derived from combining DIsoE and EUD models effectively explains the incidence of SS⩾2 after BNCT.

CONCLUSIONS

The introduced DIsoE and EUD models predict the incidence of somnolence syndrome after BNCT. The first dose-response relationship for SS⩾2 derived entirely from brain tumour patients treated with BNCT, consistent with photon radiotherapy responses, is presented.

An update on the role of focused ultrasound in neuro-oncology

PURPOSE OF REVIEW

Brain tumor treatment presents challenges for patients and clinicians, with prognosis for many of the most common brain tumors being poor. Focused ultrasound (FUS) can be deployed in several ways to circumvent these challenges, including the need to penetrate the blood-brain barrier and spare healthy brain tissue. This article reviews current FUS applications within neuro-oncology, emphasizing ongoing or recently completed clinical trials.

RECENT FINDINGS

Most clinical interest in FUS for neuro-oncology remains focused on exploring BBB disruption to enhance the delivery of standard-of-care therapeutics. More recently, the application of FUS for radiosensitization, liquid biopsy, and sonodynamic therapy is garnering increased clinical attention to assist in tumor ablation, early detection, and phenotypic diagnosis. Preclinical studies show encouraging data for the immunomodulatory effects of FUS, but these findings have yet to be tested clinically.

SUMMARY

FUS is a burgeoning area of neuro-oncology research. Data from several forthcoming large clinical trials should help clarify its role in neuro-oncology care.

Relationship between radiation dose and cerebral microbleed formation in dogs with intracranial tumors

BACKGROUND

Cerebral microbleeds (CMBs) are a possible sequela in human brain tumor patients treated with radiation therapy (RT). No such association is reported in dogs.

OBJECTIVES

To investigate whether CMBs occur in dogs after radiotherapy, and if there is an association between number and dose, and an increase over time.

ANIMALS

Thirty-four client-owned dogs irradiated for primary intracranial neoplasia. ≥2 magnetic resonance imaging (MRI) scans including susceptibility-weighted imaging (SWI) were required.

METHODS

Retrospective, observational, single-center study. Cerebral microbleeds identified on 3 T SWI were counted within the entire brain, and within low- (<20 Gy), intermediate- (20-30 Gy), and high- (>30 Gy) dose regions. A generalized linear mixed-effects model was used to analyze the relationship between the CMBs count and the predictor variables (irradiation dose, time after treatment).

RESULTS

Median follow-up time was 12.6 months (range, 1.8-37.6 months). Eighty-three MR scans were performed. In 4/15 dogs (27%, 95% CI, 10%-52%) CMBs were present at baseline. ≥1 CMBs after RT were identified in 21/34 dogs (62%, 95% CI, 45%-77%). With each month, the number of CMBs increased by 14% (95% CI, 11%-16%; P < .001). The odds of developing CMBs in the high-dose region are 4.7 times (95% CI, 3.9-5.6; P < .001) greater compared with the low-dose region.

CONCLUSION AND CLINICAL IMPORTANCE

RT is 1 possible cause of CMBs formation in dogs. Cerebral microbleeds are most likely to occur in the peritumoral high-dose volume, to be chronic, and to increase in number over time. Their clinical relevance remains unknown.

Surgically targeted radiation therapy versus stereotactic radiation therapy: A dosimetric comparison for brain metastasis resection cavities

PURPOSE

Surgically targeted radiation therapy (STaRT) with Cesium-131 seeds embedded in a collagen tile is a promising treatment for recurrent brain metastasis. In this study, the biological effective doses (BED) for normal and target tissues from STaRT plans were compared with those of external beam radiotherapy (EBRT) modalities.

METHODS

Nine patients (n = 9) with 12 resection cavities (RCs) who underwent STaRT (cumulative physical dose of 60 Gy to a depth of 5 mm from the RC edge) were replanned with CyberKnifeⓇ (CK), Gamma KnifeⓇ (GK), and intensity modulated proton therapy (IMPT) using an SRT approach (30 Gy in 5 fractions). Statistical significance comparing D95% and D90% in BED10Gy (BED10Gy95% and BED10Gy90%) and to RC + 0 to + 5 mm expansion margins, and parameters associated with radiation necrosis risk (V83Gy, V103Gy, V123Gy and V243Gy) to the normal brain were evaluated by a Wilcoxon-signed rank test.

RESULTS

For RC + 0 mm, median BED10Gy 90% for STaRT (90.1 Gy10, range: 64.1-140.9 Gy10) was significantly higher than CK (74.3 Gy10, range:59.3-80.4 Gy10, p = 0.04), GK (69.4 Gy10, range: 59.8-77.1 Gy10, p = 0.005), and IMPT (49.3 Gy10, range: 49.0-49.7 Gy10, p = 0.003), respectively. However, for the RC + 5 mm, the median BED10Gy 90% for STaRT (34.1 Gy10, range: 22.2-59.7 Gy10) was significantly lower than CK (44.3 Gy10, range: 37.8-52.4 Gy10), and IMPT (46.6 Gy10, range: 45.1-48.5 Gy10), respectively, but not significantly different from GK (34.1 Gy10, range: 22.8-47.0 Gy10). The median V243Gy was significantly higher in CK (11.7 cc, range: 4.7-20.1 cc), GK(6.2 cc, range: 2.3-11.9 cc) and IMPT (19.9 cc, range: 11.1-36.6 cc) compared to STaRT (1.1 cc, range: 0.0-7.8 cc) (p < 0.01).

CONCLUSIONS

This comparative analysis suggests a STaRT approach may treat recurrent brain tumors effectively via delivery of higher radiation doses with equivalent or greater BED up to at least 3 mm from the RC edge as compared to EBRT approaches.

Amide proton transfer-weighted CEST MRI for radiotherapy target delineation of glioblastoma: a prospective pilot study

BACKGROUND

Extensive glioblastoma infiltration justifies a 15-mm margin around the gross tumor volume (GTV) to define the radiotherapy clinical target volume (CTV). Amide proton transfer (APT)-weighted imaging could enable visualization of tumor infiltration, allowing more accurate GTV delineation. We quantified the impact of integrating APT-weighted imaging into GTV delineation of glioblastoma and compared two APT-weighted quantification methods-magnetization transfer ratio asymmetry (MTRasym) and Lorentzian difference (LD) analysis-for target delineation.

METHODS

Nine glioblastoma patients underwent an extended imaging protocol prior to radiotherapy, yielding APT-weighted MTRasym and LD maps. From both maps, biological tumor volumes were generated (BTVMTRasym and BTVLD) and added to the conventional GTV to generate biological GTVs (GTVbio,MTRasym and GTVbio,LD). Wilcoxon signed-rank tests were performed for comparisons.

RESULTS

The GTVbio,MTRasym and GTVbio,LD were significantly larger than the conventional GTV (p ≤ 0.022), with a median volume increase of 9.3% and 2.1%, respectively. The GTVbio,MTRasym and GTVbio,LD were significantly smaller than the CTV (p = 0.004), with a median volume reduction of 72.1% and 70.9%, respectively. There was no significant volume difference between the BTVMTRasym and BTVLD (p = 0.074). In three patients, BTVMTRasym delineation was affected by elevated signals at the brain periphery due to residual motion artifacts; this elevation was absent on the APT-weighted LD maps.

CONCLUSION

Larger biological GTVs compared to the conventional GTV highlight the potential of APT-weighted imaging for radiotherapy target delineation of glioblastoma. APT-weighted LD mapping may be advantageous for target delineation as it may be more robust against motion artifacts.

RELEVANCE STATEMENT

The introduction of APT-weighted imaging may, ultimately, enhance visualization of tumor infiltration and eliminate the need for the substantial 15-mm safety margin for target delineation of glioblastoma. This could reduce the risk of radiation toxicity while still effectively irradiating the tumor.

TRIAL REGISTRATION

NCT05970757 (ClinicalTrials.gov).

KEY POINTS

Integration of APT-weighted imaging into target delineation for radiotherapy is feasible. The integration of APT-weighted imaging yields larger GTVs in glioblastoma. APT-weighted LD mapping may be more robust against motion artifacts than APT-weighted MTRasym.

Determinants of cerebral radionecrosis in animal models: A systematic review

BACKGROUND

Radionecrosis is a common complication in radiation oncology, while mechanisms and risk factors have yet to be fully explored. We therefore conducted a systematic review to understand the pathogenesis and identify factors that significantly affect the development.

METHODS

We performed a systematic literature search based on the PRISMA guidelines using PubMed, Ovid, and Web of Science databases. The complete search strategy can be found as a preregistered protocol on PROSPERO (CRD42023361662).

RESULTS

We included 83 studies, most involving healthy animals (n = 72, 86.75 %). High doses of hemispherical irradiation of 30 Gy in rats and 50 Gy in mice led repeatedly to radionecrosis among different studies and set-ups. Higher dose and larger irradiated volume were associated with earlier onset. Fractionated schedules showed limited effectiveness in the prevention of radionecrosis. Distinct anatomical brain structures respond to irradiation in various ways. White matter appears to be more vulnerable than gray matter. Younger age, more evolved animal species, and genetic background were also significant factors, whereas sex was irrelevant. Only 13.25 % of the studies were performed on primary brain tumor bearing animals, no studies on brain metastases are currently available.

CONCLUSION

This systematic review identified various factors that significantly affect the induction of radionecrosis. The current state of research neglects the utilization of animal models of brain tumors, even though patients with brain malignancies constitute the largest group receiving brain irradiation. This latter aspect should be primarily addressed when developing an experimental radionecrosis model for translational implementation.

Patient-specific quality assurance of dynamically-collimated proton therapy treatment plans

BACKGROUND

The dynamic collimation system (DCS) provides energy layer-specific collimation for pencil beam scanning (PBS) proton therapy using two pairs of orthogonal nickel trimmer blades. While excellent measurement-to-calculation agreement has been demonstrated for simple cube-shaped DCS-trimmed dose distributions, no comparison of measurement and dose calculation has been made for patient-specific treatment plans.

PURPOSE

To validate a patient-specific quality assurance (PSQA) process for DCS-trimmed PBS treatment plans and evaluate the agreement between measured and calculated dose distributions.

METHODS

Three intracranial patient cases were considered. Standard uncollimated PBS and DCS-collimated treatment plans were generated for each patient using the Astroid treatment planning system (TPS). Plans were recalculated in a water phantom and delivered at the Miami Cancer Institute (MCI) using an Ion Beam Applications (IBA) dedicated nozzle system and prototype DCS. Planar dose measurements were acquired at two depths within low-gradient regions of the target volume using an IBA MatriXX ion chamber array.

RESULTS

Measured and calculated dose distributions were compared using 2D gamma analysis with 3%/3 mm criteria and low dose threshold of 10% of the maximum dose. Median gamma pass rates across all plans and measurement depths were 99.0% (PBS) and 98.3% (DCS), with a minimum gamma pass rate of 88.5% (PBS) and 91.2% (DCS).

CONCLUSIONS

The PSQA process has been validated and experimentally verified for DCS-collimated PBS. Dosimetric agreement between the measured and calculated doses was demonstrated to be similar for DCS-collimated PBS to that achievable with noncollimated PBS.

Effect of different optimization parameters in single isocenter multiple brain metastases radiosurgery

PURPOSE

Automated treatment planning for multiple brain metastases differs from traditional planning approaches. It is therefore helpful to understand which parameters for optimization are available and how they affect the plan quality. This study aims to provide a reference for designing multi-metastases treatment plans and to define quality endpoints for benchmarking the technique from a scientific perspective.

METHODS

In all, 20 patients with a total of 183 lesions were retrospectively planned according to four optimization scenarios. Plan quality was evaluated using common plan quality parameters such as conformity index, gradient index and dose to normal tissue. Therefore, different scenarios with combinations of optimization parameters were evaluated, while taking into account dependence on the number of treated lesions as well as influence of different beams.

RESULTS

Different scenarios resulted in minor differences in plan quality. With increasing number of lesions, the number of monitor units increased, so did the dose to healthy tissue and the number of interlesional dose bridging in adjacent metastases. Highly modulated cases resulted in 4-10% higher V10% compared to less complex cases, while monitor units did not increase. Changing the energy to a flattening filter free (FFF) beam resulted in lower local V12Gy (whole brain-PTV) and even though the number of monitor units increased by 13-15%, on average 46% shorter treatment times were achieved.

CONCLUSION

Although no clinically relevant differences in parameters where found, we identified some variation in the dose distributions of the different scenarios. Less complex scenarios generated visually more dose overlap; therefore, a more complex scenario may be preferred although differences in the quality metrics appear minor.

Neurologic Changes Induced by Whole-Brain Synchrotron Microbeam Irradiation: 10-Month Behavioral and Veterinary Follow-Up

PURPOSE

Novel radiation therapy approaches have increased the therapeutic efficacy for malignant brain tumors over the past decades, but the balance between therapeutic gain and radiotoxicity remains a medical hardship. Synchrotron microbeam radiation therapy, an innovative technique, deposes extremely high (peak) doses in micron-wide, parallel microbeam paths, whereas the diffusing interbeam (valley) doses lie in the range of conventional radiation therapy doses. In this study, we evaluated normal tissue toxicity of whole-brain microbeam irradiation (MBI) versus that of a conventional hospital broad beam (hBB).

METHODS AND MATERIALS

Normal Fischer rats (n = 6-7/group) were irradiated with one of the two modalities, exposing the entire brain to MBI valley/peak doses of 0/0, 5/200, 10/400, 13/520, 17/680, or 25/1000 Gy or to hBB doses of 7, 10, 13, 17, or 25 Gy. Two additional groups of rats received an MBI valley dose of 10 Gy coupled with an hBB dose of 7 or 15 Gy (groups MBI17* and MBI25*). Behavioral parameters were evaluated for 10 months after irradiation combined with veterinary observations.

RESULTS

MBI peak doses of ≥680 Gy caused acute toxicity and death. Animals exposed to hBB or MBI dose-dependently gained less weight than controls; rats in the hBB25 and MBI25* groups died within 6 months after irradiation. Increasing doses of MBI caused hyperactivity but no other detectable behavioral alterations in our tests. Importantly, no health concerns were seen up to an MBI valley dose of 17 Gy.

CONCLUSIONS

While acute toxicity of microbeam exposures depends on very high peak doses, late toxicity mainly relates to delivery of high MBI valley doses. MBI seems to have a low impact on normal rat behavior, but further tests are warranted to fully explore this hypothesis. However, high peak and valley doses are well tolerated from a veterinary point of view. This normal tissue tolerance to whole-brain, high-dose MBI reveals a promising avenue for microbeam radiation therapy, that is, therapeutic applications of microbeams that are poised for translation to a clinical environment.

Cost-effectiveness analysis of bevacizumab for cerebral radiation necrosis treatment based on real-world utility value in China

BACKGROUND

Bevacizumab shows superior efficacy in cerebral radiation necrosis (CRN) therapy, but its economic burden remains heavy due to the high drug price. This study aims to evaluate the cost-effectiveness of bevacizumab for CRN treatment from the Chinese payers' perspective.

METHODS

A decision tree model was developed to compare the costs and health outcomes of bevacizumab and corticosteroids for CRN therapy. Efficacy and safety data were derived from the NCT01621880 trial, which compared the effectiveness and safety of bevacizumab monotherapy with corticosteroids for CRN in nasopharyngeal cancer patients, and demonstrated that bevacizumab invoked a significantly higher response than corticosteroids (65.5% vs. 31.5%, P < 0.001) with no significant differences in adverse events between two groups. The utility value of the "non-recurrence" status was derived from real-world data. Costs and other utility values were collected from an authoritative Chinese network database and published literature. The primary outcomes were total costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER). The uncertainty of the model was evaluated via one-way and probabilistic sensitivity analyses.

RESULTS

Bevacizumab treatment added 0.12 (0.48 vs. 0.36) QALYs compared to corticosteroid therapy, along with incremental costs of $ 2010 ($ 4260 vs. $ 2160). The resultant ICER was $ 16,866/QALY, which was lower than the willingness-to-pay threshold of $ 38,223/QALY in China. The price of bevacizumab, body weight, and the utility value of recurrence status were the key influential parameters for ICER. Probabilistic sensitivity analysis revealed that the probability of bevacizumab being cost-effectiveness was 84.9%.

CONCLUSION

Compared with corticosteroids, bevacizumab is an economical option for CRN treatment in China.

A bibliometric analysis of radiation-induced brain injury: a research of the literature from 1998 to 2023

BACKGROUND

Radiation-induced brain injury (RIBI) is a debilitating sequela after cranial radiotherapy. Research on the topic of RIBI has gradually entered the public eye, with more innovations and applications of evidence-based research and biological mechanism research in the field of that. This was the first bibliometric analysis on RIBI, assessing brain injury related to radiation articles that were published during 1998-2023, to provide an emerging theoretical basis for the future development of RIBI.

METHODS

Literature were obtained from the Web of Science Core Collection (WOSCC) from its inception to December 31, 2023. The column of publications, author details, affiliated institutions and countries, publication year, and keywords were also recorded.

RESULTS

A total of 2543 journal articles were selected. The annual publications on RIBI fluctuated within a certain range. Journal of Neuro-oncology was the most published journal and Radiation Oncology was the most impactful one. LIMOLI CL was the most prolific author with 37 articles and shared the highest h-index with BARNETT GH. The top one country and institutions were the USA and the University of California System, respectively. Clusters analysis of co-keywords demonstrated that the temporal research trends in this field primarily focused on imaging examination and therapy for RIBI.

CONCLUSION

This study collects, visualizes, and analyzes the literature within the field of RIBI over the last 25 years to map the development process, research frontiers and hotspots, and cutting-edge directions in clinical practice and mechanisms related to RIBI.

Long-Term, Sex-Specific Effects of GCRsim and Gamma Irradiation on the Brains, Hearts, and Kidneys of Mice with Alzheimer's Disease Mutations

Understanding the hazards of space radiation is imperative as astronauts begin voyaging on missions with increasing distances from Earth's protective shield. Previous studies investigating the acute or long-term effects of specific ions comprising space radiation have revealed threats to organs generally considered radioresistant, like the brain, and have shown males to be more vulnerable than their female counterparts. However, astronauts will be exposed to a combination of ions that may result in additive effects differing from those of any one particle species. To better understand this nuance, we irradiated 4-month-old male and female, wild-type and Alzheimer's-like mice with 0, 0.5, or 0.75 Gy galactic cosmic ray simulation (GCRsim) or 0, 0.75, or 2 Gy gamma radiation (wild-type only). At 11 months, mice underwent brain and heart MRIs or behavioral tests, after which they were euthanized to assess amyloid-beta pathology, heart and kidney gene expression and fibrosis, and plasma cytokines. Although there were no changes in amyloid-beta pathology, we observed many differences in brain MRIs and behavior, including opposite effects of GCRsim on motor coordination in male and female transgenic mice. Additionally, several genes demonstrated persistent changes in the heart and kidney. Overall, we found sex- and genotype-specific, long-term effects of GCRsim and gamma radiation on the brain, heart, and kidney.

Use of dose-area product to assess plan quality in robotic radiosurgery

PURPOSE

In robotic stereotactic radiosurgery (SRS), optimal selection of collimators from a set of fixed cones must be determined manually by trial and error. A unique and uniformly scaled metric to characterize plan quality could help identify Pareto-efficient treatment plans.

METHODS

The concept of dose-area product (DAP) was used to define a measure (DAPratio) of the targeting efficiency of a set of beams by relating the integral DAP of the beams to the mean dose achieved in the target volume. In a retrospective study of five clinical cases of brain metastases with representative target volumes (range: 0.5-5.68 ml) and 121 treatment plans with all possible collimator choices, the DAPratio was determined along with other plan metrics (conformity index CI, gradient index R50%, treatment time, total number of monitor units TotalMU, radiotoxicity index f12, and energy efficiency index η50%), and the respective Spearman's rank correlation coefficients were calculated. The ability of DAPratio to determine Pareto efficiency for collimator selection at DAPratio < 1 and DAPratio < 0.9 was tested using scatter plots.

RESULTS

The DAPratio for all plans was on average 0.95 ± 0.13 (range: 0.61-1.31). Only the variance of the DAPratio was strongly dependent on the number of collimators. For each target, there was a strong or very strong correlation of DAPratio with all other metrics of plan quality. Only for R50% and η50% was there a moderate correlation with DAPratio for the plans of all targets combined, as R50% and η50% strongly depended on target size. Optimal treatment plans with CI, R50%, f12, and η50% close to 1 were clearly associated with DAPratio < 1, and plans with DAPratio < 0.9 were even superior, but at the cost of longer treatment times and higher total monitor units.

CONCLUSIONS

The newly defined DAPratio has been demonstrated to be a metric that characterizes the target efficiency of a set of beams in robotic SRS in one single and uniformly scaled number. A DAPratio < 1 indicates Pareto efficiency. The trade-off between plan quality on the one hand and short treatment time or low total monitor units on the other hand is also represented by DAPratio.

Deformation-based morphometry: a sensitive imaging approach to detect radiation-induced brain injury?

BACKGROUND

Radiotherapy is a major therapeutic approach in patients with brain tumors. However, it leads to cognitive impairments. To improve the management of radiation-induced brain sequalae, deformation-based morphometry (DBM) could be relevant. Here, we analyzed the significance of DBM using Jacobian determinants (JD) obtained by non-linear registration of MRI images to detect local vulnerability of healthy cerebral tissue in an animal model of brain irradiation.

METHODS

Rats were exposed to fractionated whole-brain irradiation (WBI, 30 Gy). A multiparametric MRI (anatomical, diffusion and vascular) study was conducted longitudinally from 1 month up to 6 months after WBI. From the registration of MRI images, macroscopic changes were analyzed by DBM and microscopic changes at the cellular and vascular levels were evaluated by quantification of cerebral blood volume (CBV) and diffusion metrics including mean diffusivity (MD). Voxel-wise comparisons were performed on the entire brain and in specific brain areas identified by DBM. Immunohistology analyses were undertaken to visualize the vessels and astrocytes.

RESULTS

DBM analysis evidenced time-course of local macrostructural changes; some of which were transient and some were long lasting after WBI. DBM revealed two vulnerable brain areas, namely the corpus callosum and the cortex. DBM changes were spatially associated to microstructural alterations as revealed by both diffusion metrics and CBV changes, and confirmed by immunohistology analyses. Finally, matrix correlations demonstrated correlations between JD/MD in the early phase after WBI and JD/CBV in the late phase both in the corpus callosum and the cortex.

CONCLUSIONS

Brain irradiation induces local macrostructural changes detected by DBM which could be relevant to identify brain structures prone to radiation-induced tissue changes. The translation of these data in patients could represent an added value in imaging studies on brain radiotoxicity.

Review of the Brain's Behaviour after Injury and Disease for Its Application in an Agent-Based Model (ABM)

The brain is the most complex organ in the human body and, as such, its study entails great challenges (methodological, theoretical, etc.). Nonetheless, there is a remarkable amount of studies about the consequences of pathological conditions on its development and functioning. This bibliographic review aims to cover mostly findings related to changes in the physical distribution of neurons and their connections-the connectome-both structural and functional, as well as their modelling approaches. It does not intend to offer an extensive description of all conditions affecting the brain; rather, it presents the most common ones. Thus, here, we highlight the need for accurate brain modelling that can subsequently be used to understand brain function and be applied to diagnose, track, and simulate treatments for the most prevalent pathologies affecting the brain.

Comparison of Risks of Late Effects From Radiation Therapy in Children Versus Adults: Insights From the QUANTEC, HyTEC, and PENTEC Efforts

Pediatric Normal Tissue Effects in the Clinic (PENTEC) seeks to refine quantitative radiation dose-volume relationships for normal-tissue complication probabilities (NTCPs) in survivors of pediatric cancer. This article summarizes the evolution of PENTEC and compares it with similar adult-focused efforts (eg, Quantitative Analysis of Normal Tissue Effects in the Clinic [QUANTEC] and Hypofractionated Treatment Effects in the Clinic [HyTEC]) with respect to content, oversight, support, scope, and methodology of literature review. It then summarizes key organ-specific findings from PENTEC in an attempt to compare NTCP estimates in children versus adults. In brief, select normal-tissue risks within developing organs and tissues (eg, maldevelopment of musculoskeletal tissue, teeth, breasts, and reproductive organs) are primarily relevant only in children. For some organs and tissues, children appear to have similar (eg, brain for necrosis, optic apparatus, parotid gland, liver), greater (eg, brain for neurocognition, cerebrovascular, breast for lactation), less (ovary), or perhaps slightly less (eg, lung) risks of toxicity versus adults. Similarly, even within the broad pediatric age range (including adolescence), for some endpoints, younger children have greater (eg, hearing and brain for neurocognition) or lesser (eg, ovary, thyroid) risks of radiation-associated toxicities. NTCP comparisons in adults versus children are often confounded by marked differences in treatment paradigms that expose normal tissues to radiation (ie, cancer types, prescribed radiation therapy dose and fields, and chemotherapy agents used). To add to the complexity, it is unclear if age is best analyzed as a continuous variable versus with age groupings (eg, infants, young children, adolescents, young adults, middle-aged adults, older adults). Further work is needed to better understand the complex manner in which age and developmental status affect risk.

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.

Leveraging radiomics and machine learning to differentiate radiation necrosis from recurrence in patients with brain metastases

OBJECTIVE

Radiation necrosis (RN) can be difficult to radiographically discern from tumor progression after stereotactic radiosurgery (SRS). The objective of this study was to investigate the utility of radiomics and machine learning (ML) to differentiate RN from recurrence in patients with brain metastases treated with SRS.

METHODS

Patients with brain metastases treated with SRS who developed either RN or tumor reccurence were retrospectively identified. Image preprocessing and radiomic feature extraction were performed using ANTsPy and PyRadiomics, yielding 105 features from MRI T1-weighted post-contrast (T1c), T2, and fluid-attenuated inversion recovery (FLAIR) images. Univariate analysis assessed significance of individual features. Multivariable analysis employed various classifiers on features identified as most discriminative through feature selection. ML models were evaluated through cross-validation, selecting the best model based on area under the receiver operating characteristic (ROC) curve (AUC). Specificity, sensitivity, and F1 score were computed.

RESULTS

Sixty-six lesions from 55 patients were identified. On univariate analysis, 27 features from the T1c sequence were statistically significant, while no features were significant from the T2 or FLAIR sequences. For clinical variables, only immunotherapy use after SRS was significant. Multivariable analysis of features from the T1c sequence yielded an AUC of 76.2% (standard deviation [SD] ± 12.7%), with specificity and sensitivity of 75.5% (± 13.4%) and 62.3% (± 19.6%) in differentiating radionecrosis from recurrence.

CONCLUSIONS

Radiomics with ML may assist the diagnostic ability of distinguishing RN from tumor recurrence after SRS. Further work is needed to validate this in a larger multi-institutional cohort and prospectively evaluate it's utility in patient care.

Dosimetric parameters predict radiation-induced temporal lobe necrosis in nasopharyngeal carcinoma patients: A systematic review and meta-analysis

This systematic review examines the role of dosimetric parameters in predicting temporal lobe necrosis (TLN) risk in nasopharyngeal carcinoma (NPC) patients treated with three-dimensional conformal RT (3D-CRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). TLN is a serious late complication that can adversely affect the quality of life of NPC patients. Understanding the relationship between dosimetric parameters and TLN can guide treatment planning and minimize radiation-related complications. A comprehensive search identified relevant studies published up to July 2023. Studies reporting on dosimetric parameters and TLN in NPC patients undergoing 3D-CRT, IMRT, and VMAT were included. TLN incidence, follow-up duration, and correlation with dosimetric parameters of the temporal lobe were analyzed. The review included 30 studies with median follow-up durations ranging from 28 to 110 months. The crude incidence of TLN varied from 2.3 % to 47.3 % and the average crude incidence of TLN is approximately 14 %. Dmax and D1cc emerged as potential predictors of TLN in 3D-CRT and IMRT-treated NPC patients. Threshold values of >72 Gy for Dmax and >62 Gy for D1cc were associated with increased TLN risk. However, other factors should also be considered, including host characteristics, tumor-specific features and therapeutic factors. In conclusion, this systematic review highlights the significance of dosimetric parameters, particularly Dmax and D1cc, in predicting TLN risk in NPC patients undergoing 3D-CRT, IMRT, and VMAT. The findings provide valuable insights that can help in developing optimal treatment planning strategies and contribute to the development of clinical guidelines in this field.

Neurocognitive Effects and Necrosis in Childhood Cancer Survivors Treated With Radiation Therapy: A PENTEC Comprehensive Review

PURPOSE

A PENTEC review of childhood cancer survivors who received brain radiation therapy (RT) was performed to develop models that aid in developing dose constraints for RT-associated central nervous system (CNS) morbidities.

METHODS AND MATERIALS

A comprehensive literature search, through the PENTEC initiative, was performed to identify published data pertaining to 6 specific CNS toxicities in children treated with brain RT. Treatment and outcome data on survivors were extracted and used to generate normal tissue complication probability (NTCP) models.

RESULTS

The search identified investigations pertaining to 2 of the 6 predefined CNS outcomes: neurocognition and brain necrosis. For neurocognition, models for 2 post-RT outcomes were developed to (1) calculate the risk for a below-average intelligence quotient (IQ) (IQ <85) and (2) estimate the expected IQ value. The models suggest that there is a 5% risk of a subsequent IQ <85 when 10%, 20%, 50%, or 100% of the brain is irradiated to 35.7, 29.1, 22.2, or 18.1 Gy, respectively (all at 2 Gy/fraction and without methotrexate). Methotrexate (MTX) increased the risk for an IQ <85 similar to a generalized uniform brain dose of 5.9 Gy. The model for predicting expected IQ also includes the effect of dose, age, and MTX. Each of these factors has an independent, but probably cumulative effect on IQ. The necrosis model estimates a 5% risk of necrosis for children after 59.8 Gy or 63.6 Gy (2 Gy/fraction) to any part of the brain if delivered as primary RT or reirradiation, respectively.

CONCLUSIONS

This PENTEC comprehensive review establishes objective relationships between patient age, RT dose, RT volume, and MTX to subsequent risks of neurocognitive injury and necrosis. A lack of consistent RT data and outcome reporting in the published literature hindered investigation of the other predefined CNS morbidity endpoints.

Brain and Brain Stem Necrosis After Reirradiation for Recurrent Childhood Primary Central Nervous System Tumors: A PENTEC Comprehensive Review

PURPOSE

Reirradiation is increasingly used in children and adolescents/young adults (AYA) with recurrent primary central nervous system tumors. The Pediatric Normal Tissue Effects in the Clinic (PENTEC) reirradiation task force aimed to quantify risks of brain and brain stem necrosis after reirradiation.

METHODS AND MATERIALS

A systematic literature search using the PubMed and Cochrane databases for peer-reviewed articles from 1975 to 2021 identified 92 studies on reirradiation for recurrent tumors in children/AYA. Seventeen studies representing 449 patients who reported brain and brain stem necrosis after reirradiation contained sufficient data for analysis. While all 17 studies described techniques and doses used for reirradiation, they lacked essential details on clinically significant dose-volume metrics necessary for dose-response modeling on late effects. We, therefore, estimated incidences of necrosis with an exact 95% CI and qualitatively described data. Results from multiple studies were pooled by taking the weighted average of the reported crude rates from individual studies.

RESULTS

Treated cancers included ependymoma (n = 279 patients; 7 studies), medulloblastoma (n = 98 patients; 6 studies), any CNS tumors (n = 62 patients; 3 studies), and supratentorial high-grade gliomas (n = 10 patients; 1 study). The median interval between initial and reirradiation was 2.3 years (range, 1.2-4.75 years). The median cumulative prescription dose in equivalent dose in 2-Gy fractions (EQD22; assuming α/β value = 2 Gy) was 103.8 Gy (range, 55.8-141.3 Gy). Among 449 reirradiated children/AYA, 22 (4.9%; 95% CI, 3.1%-7.3%) developed brain necrosis and 14 (3.1%; 95% CI, 1.7%-5.2%) developed brain stem necrosis with a weighted median follow-up of 1.6 years (range, 0.5-7.4 years). The median cumulative prescription EQD22 was 111.4 Gy (range, 55.8-141.3 Gy) for development of any necrosis, 107.7 Gy (range, 55.8-141.3 Gy) for brain necrosis, and 112.1 Gy (range, 100.2-117 Gy) for brain stem necrosis. The median latent period between reirradiation and the development of necrosis was 5.7 months (range, 4.3-24 months). Though there were more events among children/AYA undergoing hypofractionated versus conventionally fractionated reirradiation, the differences were not statistically significant (P = .46).

CONCLUSIONS

Existing reports suggest that in children/AYA with recurrent brain tumors, reirradiation with a total EQD22 of about 112 Gy is associated with an approximate 5% to 7% incidence of brain/brain stem necrosis after a median follow-up of 1.6 years (with the initial course of radiation therapy being given with conventional prescription doses of ≤2 Gy per fraction and the second course with variable fractionations). We recommend a uniform approach for reporting dosimetric endpoints to derive robust predictive models of late toxicities following reirradiation.

Comparative analysis of bevacizumab and LITT for treating radiation necrosis in previously radiated CNS neoplasms: a systematic review and meta-analysis

PURPOSE

Radiation necrosis (RN) is a local inflammatory reaction that arises in response to radiation injury and may cause significant morbidity. This study aims to evaluate and compare the efficacy of bevacizumab and laser interstitial thermal therapy (LITT) in treating RN in patients with previously radiated central nervous system (CNS) neoplasms.

METHODS

PubMed, Cochrane, Scopus, and EMBASE databases were screened. Studies of patients with radiation necrosis from primary or secondary brain tumors were included. Indirect meta-analysis with random-effect modeling was performed to compare clinical and radiological outcomes.

RESULTS

Twenty-four studies were included with 210 patients in the bevacizumab group and 337 patients in the LITT group. Bevacizumab demonstrated symptomatic improvement/stability in 87.7% of cases, radiological improvement/stability in 86.2%, and steroid wean-off in 45%. LITT exhibited symptomatic improvement/stability in 71.2%, radiological improvement/stability in 64.7%, and steroid wean-off in 62.4%. Comparative analysis revealed statistically significant differences favoring bevacizumab in symptomatic improvement/stability (p = 0.02), while no significant differences were observed in radiological improvement/stability (p = 0.27) or steroid wean-off (p = 0.90). The rates of adverse reactions were 11.2% for bevacizumab and 14.9% for LITT (p = 0.66), with the majority being grade 2 or lower (72.2% for bevacizumab and 62.5% for LITT).

CONCLUSION

Both bevacizumab and LITT exhibited favorable clinical and radiological outcomes in managing RN. Bevacizumab was found to be associated with better symptomatic control compared to LITT. Patient-, diagnosis- and lesion-related factors should be considered when choosing the ideal treatment modality for RN to enhance overall patient outcomes.

Neurological complications of modern radiotherapy for head and neck cancer

Radiotherapy is one of the mainstay treatment modalities for the management of non-metastatic head and neck cancer (HNC). Notable improvements in treatment outcomes have been observed in the recent decades. Modern radiotherapy techniques, such as intensity-modulated radiotherapy and charged particle therapy, have significantly improved tumor target conformity and enabled better preservation of normal structures. However, because of the intricate anatomy of the head and neck region, multiple critical neurological structures such as the brain, brainstem, spinal cord, cranial nerves, nerve plexuses, autonomic pathways, brain vasculature, and neurosensory organs, are variably irradiated during treatment, particularly when tumor targets are in close proximity. Consequently, a diverse spectrum of late neurological sequelae may manifest in HNC survivors. These neurological complications commonly result in irreversible symptoms, impair patients' quality of life, and contribute to a substantial proportion of non-cancer deaths. Although the relationship between radiation dose and toxicity has not been fully elucidated for all complications, appropriate application of dosimetric constraints during radiotherapy planning may reduce their incidence. Vigilant surveillance during the course of survivorship also enables early detection and intervention. This article endeavors to provide a comprehensive review of the various neurological complications of modern radiotherapy for HNC, summarize the current incidence data, discuss methods to minimize their risks during radiotherapy planning, and highlight potential strategies for managing these debilitating toxicities.

Predicting neuropsychological late effects in pediatric brain tumor survivors using the Neurological Predictor Scale and the Pediatric Neuro-Oncology Rating of Treatment Intensity

OBJECTIVE

The Neurological Predictor Scale (NPS) quantifies cumulative exposure to tumor- and treatment-related neurological risks. The Pediatric Neuro-Oncology Rating of Treatment Intensity (PNORTI) measures the intensity of different treatment modalities, but research is needed to establish whether it is associated with late effects. This study evaluated the predictive validity of the NPS and PNORTI for neuropsychological outcomes in pediatric brain tumor survivors.

METHOD

A retrospective chart review was completed of pediatric brain tumor survivors (PBTS) (n = 161, Mage = 13.47, SD = 2.80) who were at least 2 years from the end of tumor-directed treatment. Attention, intellectual functioning, perceptual reasoning, processing speed, verbal reasoning, and working memory were analyzed in relation to the NPS and PNORTI.

RESULTS

NPS scores ranged from 1 to 11 (M = 5.57, SD = 2.27) and PNORTI scores ranged from 1 (n = 101; 62.7%) to 3 (n = 18; 11.2%). When controlling for age, sex, SES factors, and time since treatment, NPS scores significantly predicted intellectual functioning [F(7,149) = 12.86, p < .001, R2 = .38] and processing speed [F(7,84) = 5.28, p < .001, R2 = .31]. PNORTI scores did not significantly predict neuropsychological outcomes.

CONCLUSIONS

The findings suggest that the NPS has value in predicting IF and processing speed above-and-beyond demographic variables. The PNORTI was not associated with neuropsychological outcomes. Future research should consider establishing clinical cutoff scores for the NPS to help determine which survivors are most at risk for neuropsychological late effects and warrant additional assessment.

Evaluation of specific RBE in different cells of hippocampus under high-dose proton irradiation in rats

The study aimed to determine the specific relative biological effectiveness (RBE) of various cells in the hippocampus following proton irradiation. Sixty Sprague-Dawley rats were randomly allocated to 5 groups receiving 20 or 30 Gy of proton or photon irradiation. Pathomorphological neuronal damage in the hippocampus was assessed using Hematoxylin-eosin (HE) staining. The expression level of NeuN, Nestin, Caspase-3, Olig2, CD68 and CD45 were determined by immunohistochemistry (IHC). The RBE range established by comparing the effects of proton and photon irradiation at equivalent biological outcomes. Proton20Gy induced more severe damage to neurons than photon20Gy, but showed no difference compared to photon30Gy. The RBE of neuron was determined to be 1.65. Similarly, both proton20Gy and proton30Gy resulted in more inhibition of oligodendrocytes and activation of microglia in the hippocampal regions than photon20Gy and photon30Gy. However, the expression of Olig2 was higher and CD68 was lower in the proton20Gy group than in the photon30Gy group. The RBE of oligodendrocyte and microglia was estimated to be between 1.1 to 1.65. For neural stem cells (NSCs) and immune cells, there were no significant difference in the expression of Nestin and CD45 between proton and photon irradiation (both 20 and 30 Gy). Therefore, the RBE for NSCs and immune cell was determined to be 1.1. These findings highlight the varying RBE values of different cells in the hippocampus in vivo. Moreover, the actual RBE of the hippocampus may be higher than 1.1, suggesting that using as RBE value of 1.1 in clinical practice may underestimate the toxicities induced by proton radiation.

Characterization of cerebral radiation necrosis following the treatment of sinonasal malignancies

Objectives

Our study aims to determine the incidence and potential risk factors for cerebral radiation necrosis (CRN) following treatment of sinonasal malignancies.

Methods

One hundred thirty-two patients diagnosed with sinonasal malignancies over an 18-year period were identified at two institutions. Forty-six patients meeting inclusion criteria and treated with radiation therapy were included for analysis. Demographic and clinical-pathologic characteristics were collected and reviewed. Post-treatment magnetic resonance imaging (MRI) at least 1 year following treatment was reviewed to determine presence or absence of CRN.

Results

CRN was identified on MRI in 8 of 46 patients (17.4%) following radiation treatment. Patients with a history of reirradiation were more likely to develop CRN (50% vs. 10.5%, p < .05). The BEDs of radiation were also higher in CRN patients compared to non-CRN patients, but this difference was not significant (p > .05). CRN patients had a higher proportion of tumors with skull base involvement than non-CRN patients (100% vs. 57.9%, p = .037). Demographics, comorbidities, pathology, primary tumor subsite, chemotherapy use, and stage of disease demonstrated no significant increase in risk of CRN.

Conclusions

Reirradiation and tumor skull base involvement were significant risk factors associated with CRN. Higher average total prescribed and BEDs of radiation were seen in the CRN groups, but these differences were not statistically significant. Gender, comorbidities, tumor subsite, tumor location, and treatment type were not significantly different between groups.

Level of evidence

Level 3.

Prospective Analysis of Radiation-Induced Contrast Enhancement and Health-Related Quality of Life After Proton Therapy for Central Nervous System and Skull Base Tumors

PURPOSE

Intracerebral radiation-induced contrast enhancement (RICE) can occur after photon as well as proton beam therapy (PBT). This study evaluated the incidence, characteristics, and risk factors of RICE after PBT delivered to, or in direct proximity to, the brain and its effect on health-related quality of life (HRQoL).

METHODS AND MATERIALS

Four hundred twenty-one patients treated with pencil beam scanning PBT between 2017 and 2021 were included. Follow-up included clinical evaluation and contrast-enhanced magnetic resonance imaging at 3, 6, and 12 months after treatment completion and annually thereafter. RICE was graded according to Common Terminology Criteria for Adverse Events version 4, and HRQoL parameters were assessed via European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ)-C30 questionnaires.

RESULTS

The median follow-up was 24 months (range, 6-54), and median dose to 1% relative volume of noninvolved central nervous system (D1%CNS) was 54.3 Gy relative biologic effectiveness (RBE; range, 30-76 Gy RBE). The cumulative RICE incidence was 15% (n = 63), of which 10.5% (n = 44) were grade 1, 3.1% (n = 13) were grade 2, and 1.4% (n = 6) were grade 3. No grade 4 or 5 events were observed. Twenty-six of 63 RICE (41.3%) had resolved at the latest follow-up. The median onset after PBT and duration of RICE in patients in whom the lesions resolved were 11.8 and 9.0 months, respectively. On multivariable analysis, D1%CNS > 57.6 Gy RBE, previous in-field radiation, and diabetes mellitus were identified as significant risk factors for RICE development. Previous radiation was the only factor influencing the risk of symptomatic RICE. After PBT, general HRQoL parameters were not compromised. In a matched cohort analysis of 54/50 patients with and without RICE, no differences in global health score or functional and symptom scales were seen.

CONCLUSIONS

The overall incidence of clinically relevant RICE after PBT is very low and has no significant negative effect on long-term patient QoL.

Prognosis versus Actual Outcomes in Stereotactic Radiosurgery of Brain Metastases: Reliability of Common Prognostic Parameters and Indices

This study aims to evaluate the clinical outcome of stereotactic radiosurgery as the sole treatment for brain metastases and to assess prognostic factors influencing survival. A total of 108 consecutive patients with 213 metastases were retrospectively analyzed. Treatment was determined with close-meshed MRI follow-up. Various prognostic factors were assessed, and several prognostic indices were compared regarding their reliability to estimate overall survival. Median overall survival was 15 months; one-year overall survival was 50.5%. Both one- and two-year local controls were 90.9%. The rate of new metastases after SRS was 49.1%. Multivariate analysis of prognostic factors revealed that the presence of extracranial metastases, male sex, lower KPI, and progressive extracranial disease were significant risk factors for decreased survival. Of all evaluated prognostic indices, the Basic Score for Brain Metastases (BSBMs) showed the best correlation with overall survival. A substantial survival advantage was found for female patients after SRS when compared to male patients (18 versus 9 months, p = 0.003). SRS of brain metastasis is a safe and effective treatment option when frequent monitoring for new metastases with MRI is performed. Common prognostic scores lack reliable estimation of survival times. Female sex should be considered as an additional independent positive prognostic factor influencing survival.

A systematic review and meta-analysis of radiotherapy and particle beam therapy for skull base chondrosarcoma: TRP-chondrosarcoma 2024

Introduction

Chondrosarcoma is a rare malignant bone tumor. Particle beam therapy (PT) can concentrate doses to targets while reducing adverse events. A meta-analysis based on a literature review was performed to examine the efficacy of PT and photon radiotherapy for skull base chondrosarcoma.

Methods

The meta-analysis was conducted using 21 articles published from 1990 to 2022.

Results

After PT, the 3- and 5-year overall survival (OS) rates were 94.1% (95% confidence interval [CI]: 91.0-96.2%) and 93.9% (95% CI: 90.6-96.1%), respectively, and the 3- and 5-year local control rates were 95.4% (95% CI: 92.0-97.4%) and 90.1% (95% CI: 76.8-96.0%), respectively. Meta-regression analysis revealed a significant association of PT with a superior 5-year OS rate compared to three-dimensional conformal radiotherapy (p < 0.001). In the studies used in the meta-analysis, the major adverse event of grade 2 or higher was temporal lobe necrosis (incidence 1-18%, median 7%).

Conclusion

PT for skull base chondrosarcoma had a good outcome and may be a valuable option among radiotherapy modalities. However, high-dose postoperative irradiation of skull base chondrosarcoma can cause adverse events such as temporal lobe necrosis.