Cerebral radiation necrosis: a review of the pathobiology, diagnosis and management considerations

Successful treatment of quadriparesis from radiation myelopathy with bevacizumab in a patient with metastatic breast cancer

Radiation myelopathy (RM) is rare condition defined as injury to the spinal cord by ionising radiation. Due to improved survival in patients with advanced malignancies, there is a renewed interest in recognition and treatment of RM. There are very few reports on treatment of RM. A 64-year-old woman with metastatic oestrogen receptor, progesterone receptor weakly positive and human epidermal growth factor 2 negative breast, stereotactic radiosurgeries to brain metastases and a history of reradiation to the cervical spinal cord presented with neck pain, arm weakness, hyperreflexia and gait ataxia. RM was suspected and the patient was started on high dose corticosteroid therapy. However, the patient's condition deteriorated and she developed quadriparesis. A timely treatment with an antivascular endothelial growth factor antibody, bevacizumab reversed her neurological deficits and preserved her walking ability. Our case illustrates a prompt diagnosis and successful treatment of RM with bevacizumab.

Intracranial arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) has evolved over the last 10 years. It is now possible to see that obliteration continues for up to 10 years and that the final obliteration rate may be between 85% and 90%. Improved imaging has made the treatment more efficient and has reduced the complications. It is possible to treat larger AVMs in a single session than was previously thought possible without increases in the complication rates. In addition, treatments of larger lesions can be staged. The use of 3D rotating angiography produces remarkable images which can be imported into GammaPlan. On the other hand efforts are ongoing to avoid the need for digital subtraction angiography, which would make the treatment a lot more comfortable.

Treatment of Radiation-Induced Brain Necrosis

Radiation-induced brain necrosis (RBN) is a serious complication of intracranial as well as skull base tumors after radiotherapy. In the past, due to the lack of effective treatment, radiation brain necrosis was considered to be progressive and irreversible. With better understanding in histopathology and neuroimaging, the occurrence and development of RBN have been gradually clarified, and new treatment methods are constantly emerging. In recent years, some scholars have tried to treat RBN with bevacizumab, nerve growth factor, and gangliosides and have achieved similar results. Some cases of brain necrosis can be repairable and reversible. We aimed to summarize the incidence, pathogenesis, and treatment of RBN.

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases

INTRODUCTIO

Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

PATIENTS AND METHODS

We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

RESULTS

We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

CONCLUSION

SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.

Current emerging MRI tools for radionecrosis and pseudoprogression diagnosis

PURPOSE OF REVIEW

This review aims to cover current MRI techniques for assessing treatment response in brain tumors, with a focus on radio-induced lesions.

RECENT FINDINGS

Pseudoprogression and radionecrosis are common radiological entities after brain tumor irradiation and are difficult to distinguish from real progression, with major consequences on daily patient care. To date, shortcomings of conventional MRI have been largely recognized but morphological sequences are still used in official response assessment criteria. Several complementary advanced techniques have been proposed but none of them have been validated, hampering their clinical use. Among advanced MRI, brain perfusion measures increase diagnostic accuracy, especially when added with spectroscopy and susceptibility-weighted imaging. However, lack of reproducibility, because of several hard-to-control variables, is still a major limitation for their standardization in routine protocols. Amide Proton Transfer is an emerging molecular imaging technique that promises to offer new metrics by indirectly quantifying intracellular mobile proteins and peptide concentration. Preliminary studies suggest that this noncontrast sequence may add key biomarkers in tumor evaluation, especially in posttherapeutic settings.

SUMMARY

Benefits and pitfalls of conventional and advanced imaging on posttreatment assessment are discussed and the potential added value of APT in this clinicoradiological evolving scenario is introduced.

Central Nervous System Complications Among Oncology Patients

Cancer treatment related injury to the central nervous system (CNS) is well-recognized in the setting of brain-directed radiation therapies and conventional and novel systemic anticancer therapies. Late-delayed treatment-induced CNS complications frequently result in permanent neurologic disability. Therapeutic options are supportive with limited clinical benefit, whereby alteration or discontinuation of the overall antineoplastic treatment plan is frequently necessary to prevent further neurologic injury. Better identification of patients at high risk for developing late CNS toxicities, neuroprotective strategies with modification of existing antineoplastic treatment regimens, and research efforts directed at earlier recognition and improved treatment of central neurologic complications are paramount.

Risk Factors for Radiation Necrosis in Patients Undergoing Cranial Stereotactic Radiosurgery

Simple Summary

Radiation necrosis is a known complication after stereotactic radiosurgery of intracranial tumors. We evaluated 388 patients who underwent stereotactic radiosurgery at our institution. The most common tumors were metastases (47.2%), followed by vestibular schwannomas (32.2%) and meningiomas (13.4%). 15.7% developed radiation necrosis after a median of 8 months. According to our data, larger tumor diameter (HR 1.065) and higher radiation dose (HR 1.302) were associated with an increased risk of radiation necrosis independently of tumor type. Advanced age was shown to be a risk factor for radiation necrosis only in cases with metastasis (HR 1.066). The data from this study suggest that the development of radiation necrosis is dependent on size and dose, not on the type of the neoplasm.

Abstract

Purpose: single-staged stereotactic radiosurgery (SRS) is an established part of the multimodal treatment in neuro-oncology. Radiation necrosis after high-dose irradiation is a known complication, but there is a lack of evidence about the risk factors. The aim of this study was to evaluate possible risk factors for radiation necrosis in patients undergoing radiosurgery. Methods: patients treated with radiosurgery between January 2004 and November 2020 were retrospectively analyzed. The clinical data, imaging and medication were gathered from electronic patient records. The largest diameter of the tumors was measured using MRI scans in T1 weighted imaging with gadolinium and the edema in T2 weighted sequences. The diagnosis of a radiation necrosis was established analyzing imaging criteria combined with clinical course or pathologically confirmed by subsequent surgical intervention. Patients developing radiation necrosis detected after SRS were compared to patients without evidence of an overshooting irradiation reaction. Results: 388 patients were included retrospectively, 61 (15.7%) of whom developed a radiation necrosis. Median follow-up was 24 (6–62) months with a radiation necrosis after 8 (6–12) months. The most frequent tumors were metastases in 47.2% of the cases, followed by acoustic neuromas in 32.2% and meningiomas in 13.4%. Seventy-three (18.9%) patients already underwent one or more previous radiosurgical procedures for different lesions. The mean largest diameter of the tumors amounted to 16.3 mm (±6.1 mm). The median—80%—isodose administered was 16 (14–25) Gy. Of the radiation necroses, 25 (43.1%) required treatment, in 23 (39.7%) thereof, medical treatment was applied and in 2 (3.4%) cases, debulking surgery was performed. In this study, significantly more radiation necroses arose in patients with higher doses (HR 1.3 [CI 1.2; 1.5], p < 0.001) leading to a risk increment of over 180% between a radiation isodose of 14 and 20 Gy. The maximum diameter was a second significant risk factor (p = 0.028) with an HR of 1065 for every 1 mm increase in multivariate analysis. Conclusion: large diameter and high doses were reliable independent risk factors leading to more frequent radiation necroses, regardless of tumor type in patients undergoing radiosurgery. Alternative therapeutic procedures may be considered in lesions with large volume and an expected high radiation doses due to the increased risk of developing radiation necrosis.

Tumor habitat analysis by magnetic resonance imaging distinguishes tumor progression from radiation necrosis in brain metastases after stereotactic radiosurgery

OBJECTIVES

The identification of viable tumor after stereotactic radiosurgery (SRS) is important for future targeted therapy. This study aimed to determine whether tumor habitat on structural and physiologic MRI can distinguish viable tumor from radiation necrosis of brain metastases after SRS.

METHOD

Multiparametric contrast-enhanced T1- and T2-weighted imaging, apparent diffusion coefficient (ADC), and cerebral blood volume (CBV) were obtained from 52 patients with 69 metastases, showing enlarging enhancing masses after SRS. Voxel-wise clustering identified three structural MRI habitats (enhancing, solid low-enhancing, and nonviable) and three physiologic MRI habitats (hypervascular cellular, hypovascular cellular, and nonviable). Habitat-based predictors for viable tumor or radiation necrosis were identified by logistic regression. Performance was validated using the area under the curve (AUC) of the receiver operating characteristics curve in an independent dataset with 24 patients.

RESULTS

None of the physiologic MRI habitats was indicative of viable tumor. Viable tumor was predicted by a high-volume fraction of solid low-enhancing habitat (low T2-weighted and low CE-T1-weighted values; odds ratio [OR] 1.74, p <.001) and a low-volume fraction of nonviable tissue habitat (high T2-weighted and low CE-T1-weighted values; OR 0.55, p <.001). Combined structural MRI habitats yielded good discriminatory ability in both development (AUC 0.85, 95% confidence interval [CI]: 0.77-0.94) and validation sets (AUC 0.86, 95% CI:0.70-0.99), outperforming single ADC (AUC 0.64) and CBV (AUC 0.58) values. The site of progression matched with the solid low-enhancing habitat (72%, 8/11).

CONCLUSION

Solid low-enhancing and nonviable tissue habitats on structural MRI can help to localize viable tumor in patients with brain metastases after SRS.

KEY POINTS

• Structural MRI habitats helped to differentiate viable tumor from radiation necrosis. • Solid low-enhancing habitat was most helpful to find viable tumor. • Providing spatial information, the site of progression matched with solid low-enhancing habitat.

Exosomes Derived From Adipose-Derived Mesenchymal Stem Cells Ameliorate Radiation-Induced Brain Injury by Activating the SIRT1 Pathway

Objective

Studies have shown that the therapeutic effects of mesenchymal stem cells (MSCs) are mediated in a paracrine manner, mainly through extracellular vesicles such as exosomes. Here, we designed a study to investigate whether exosomes derived from adipose-derived mesenchymal stem cells (ADMSC-Exos) had protective effects in a rat model of radiation-induced brain injury and in microglia.

Methods

Male adult Sprague-Dawley (SD) rats were randomly divided into three groups: the control group, the radiation group (30 Gy), and the radiation + exosomes group (30 Gy + 100 ug exosomes). Meanwhile, microglia were divided into four groups: the control group, the radiation group (10 Gy), the radiation + exosomes group (10 Gy + 4 ug exosomes), and radiation + exosomes + EX527 group (10 Gy + 4 ug exosomes + 100 nM EX527). Tissue samples and the levels of oxidative stress and inflammatory factors in each group were compared.

Results

Statistical analysis showed that after irradiation, ADMSC-Exos intervention in vivo significantly reduced the levels of caspase-3, malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α), interleukin-4 (IL-4), and promoted the recovery of superoxide dismutase (SOD), catalase (CAT), IL-4, and IL-10. Moreover, ADMSC-Exos intervention inhibited microglial infiltration and promoted the expression of SIRT1. Furthermore, the results in vitro showed that the above effects of ADMSC-Exos could be reversed by SIRT-1 inhibitor EX527.

Conclusion

This study demonstrated that ADMSC-Exos exerted protective effects against radiation-induced brain injury by reducing oxidative stress, inflammation and microglial infiltration via activating the SIRT1 pathway. ADMSC-Exos may serve as a promising therapeutic tool for radiation-induced brain injury.

Bevacizumab vs laser interstitial thermal therapy in cerebral radiation necrosis from brain metastases: a systematic review and meta-analysis

PURPOSE

Radiation necrosis (RN) represents a serious post-radiotherapy complication in patients with brain metastases. Bevacizumab and laser interstitial thermal therapy (LITT) are viable treatment options, but direct comparative data is scarce. We reviewed the literature to compare the two treatment strategies.

METHODS

PubMed, EMBASE, Scopus, and Cochrane databases were searched. All studies of patients with RN from brain metastases treated with bevacizumab or LITT were included. Treatment outcomes were analyzed using indirect meta-analysis with random-effect modeling.

RESULTS

Among the 18 studies included, 143 patients received bevacizumab and 148 underwent LITT. Both strategies were equally effective in providing post-treatment symptomatic improvement (P = 0.187, I² = 54.8%), weaning off steroids (P = 0.614, I² = 25.5%), and local lesion control (P = 0.5, I² = 0%). Mean number of lesions per patient was not statistically significant among groups (P = 0.624). Similarly, mean T1-contrast-enhancing pre-treatment volumes were not statistically different (P = 0.582). Patterns of radiological responses differed at 6-month follow-ups, with rates of partial regression significantly higher in the bevacizumab group (P = 0.001, I² = 88.9%), and stable disease significantly higher in the LITT group (P = 0.002, I² = 81.9%). Survival rates were superior in the LITT cohort, and statistical significance was reached at 18 months (P = 0.038, I² = 73.7%). Low rates of adverse events were reported in both groups (14.7% for bevacizumab and 12.2% for LITT).

CONCLUSION

Bevacizumab and LITT can be safe and effective treatments for RN from brain metastases. Clinical and radiological outcomes are mostly comparable, but LITT may relate with superior survival benefits in select patients. Further studies are required to identify the best patient candidates for each treatment group.

Long-term metabolic evolution of brain metastases with suspected radiation necrosis following stereotactic radiosurgery: longitudinal assessment by F-DOPA PET

BACKGROUND

The evolution of radiation necrosis (RN) varies depending on the combination of radionecrotic tissue and active tumor cells. In this study, we characterized the long-term metabolic evolution of RN by sequential PET/CT imaging with 3,4-dihydroxy-6-[18F]-fluoro-l-phenylalanine (F-DOPA) in patients with brain metastases following stereotactic radiosurgery (SRS).

METHODS

Thirty consecutive patients with 34 suspected radionecrotic brain metastases following SRS repeated F-DOPA PET/CT every 6 months or yearly in addition to standard MRI monitoring. Diagnoses of local progression (LP) or RN were confirmed histologically or by clinical follow-up. Semi-quantitative parameters of F-DOPA uptake were extracted at different time points, and their diagnostic performances were compared with those of corresponding contrast-enhanced MRI.

RESULTS

Ninety-nine F-DOPA PET scans were acquired over a median period of 18 (range: 12-66) months. Median follow-up from the baseline F-DOPA PET/CT was 48 (range 21-95) months. Overall, 24 (70.6%) and 10 (29.4%) lesions were classified as RN and LP, respectively. LP occurred after a median of 18 (range: 12-30) months from baseline PET. F-DOPA tumor-to-brain ratio (TBR) and relative standardized uptake value (rSUV) increased significantly over time in LP lesions, while remaining stable in RN lesions. The parameter showing the best diagnostic performance was rSUV (accuracy = 94.1% for the optimal threshold of 1.92). In contrast, variations of the longest tumor dimension measured on contrast-enhancing MRI did not distinguish between RN and LP.

CONCLUSION

F-DOPA PET has a high diagnostic accuracy for assessing the long-term evolution of brain metastases following SRS.

Frameless Stereotactic Radiosurgery With Linear Accelerator (LINAC)-Based Technology for Brain Metastases: Outcomes Analysis in 141 Patients

Objectives Brain metastases (BM) are the most common intracranial tumors in adults. Surgery and frame-based stereotactic radiosurgery (SRS) are well-described treatment options. Frameless SRS is an emerging BM treatment option offering fewer side effects. The aim of this study was to describe the therapeutic outcomes and toxicity of frameless SRS with linear accelerator (LINAC)-based technology for BM treatment in our institution. Materials and methods We performed a retrospective study including all adult patients treated with frameless SRS with LINAC-based technology for BM between October 2010 and July 2016. Patients were followed routinely with MRI scans at three-month intervals. Primary endpoints were progression-free survival, local control, overall survival, and toxicity related to the treatment. All survival times were computed with the Kaplan-Meier method. All cumulative incidences were computed using competing risk analyses. Results A total of 194 metastatic lesions in 141 patients were treated in a 69-month interval. At the time of analysis, 33 patients were still alive, with a median follow-up time of 25.1 months. The overall median survival was 8.7 months. The median progression-free survival was 5.3 months. Local recurrence as a first event was 25% and 38% at one and two years, respectively, while distant brain recurrence as a first event was 18% and 21%. Death before any brain event occurred in 31% of patients. The cumulative incidence of radiation necrosis as a first brain event was 2% at one and two years. Conclusions The treatment of BM with LINAC-based frameless SRS in our institution had an overall and progression-free survival comparable with the literature for frameless SRS and for conventional frame-based SRS while being less invasive and more comfortable for the patient. In our study, frameless SRS with LINAC technology seems to be safe for BM treatment with minimal rates of radiation necrosis.

Laser interstitial thermal therapy for treatment of cerebral radiation necrosis

Radiation necrosis is a well described complication after radiosurgical treatment of intracranial pathologies - best recognized after the treatment of patients with arteriovenous malformations and brain metastases but possibly also affecting patients treated with radiosurgery for meningioma. The pathophysiology of radiation necrosis is still not well understood but is most likely a secondary local tissue inflammatory response to brain tissue injured by radiation. Radiation necrosis in brain metastases patients may present radiographically and behave clinically like recurrent tumor. Differentiation between radiation necrosis and recurrent tumor has been difficult based on radiographic changes alone. Biopsy or craniotomy therefore remains the gold standard method of diagnosis. For symptomatic patients, corticosteroids are first-line therapy, but patients may fail medical management due to intolerance of chronic steroids or persistence of symptoms. In these cases, open surgical resection has been shown to be successful in management of surgically amenable lesions but may be suboptimal in patients with deep-seated lesions or extensive prior cranial surgical history, both carrying high risk for peri-operative morbidity. Laser interstitial thermal therapy has emerged as a viable, alternative surgical option. In addition to allowing access to tissue for diagnosis, thermal treatment of the lesion can also be delivered precisely and accurately under real-time imaging guidance. This review highlights the pertinent studies that have shaped the impetus for use of laser interstitial thermal therapy in the treatment of radiation necrosis, reviewing indications, outcomes, and nuances toward successful application of this technology in patients with suspected radiation necrosis.

Bevacizumab Treatment of Radiation-Induced Brain Necrosis: A Systematic Review

BACKGROUND

Radiation brain necrosis (RBN) is a serious complication in patients receiving radiotherapy for intracranial disease. Many studies have investigated the efficacy and safety of bevacizumab in patients with RBN. In the present study, we systematically reviewed the medical literature for studies reporting the efficacy and safety of bevacizumab, as well as for studies comparing bevacizumab with corticosteroids.

MATERIALS AND METHODS

We searched PubMed, Cochrane library, EMBASE, and ClinicalTrials.gov from their inception through 1 March, 2020 for studies that evaluated the efficacy and safety of bevacizumab in patients with RBN. Two investigators independently performed the study selection, data extraction, and data synthesis.

RESULTS

Overall, the present systematic review included 12 studies (eight retrospective, two prospective, and two randomized control trials [RCTs]) involving 236 patients with RBN treated who were treated with bevacizumab. The two RCTs also had control arms comprising patients with RBN who were treated with corticosteroids/placebo (n=57). Radiographic responses were recorded in 84.7% (200/236) of patients, and radiographic progression was observed in 15.3% (36/236). Clinical improvement was observed in 91% (n=127) of responding patients among seven studies (n=113). All 12 studies reported volume reduction on T1 gadolinium enhancement MRI (median: 50%, range: 26%-80%) and/or T2 FLAIR MRI images (median: 59%, range: 48%-74%). In total, 46 responding patients (34%) had recurrence. The two RCTs revealed significantly improved radiographic response in patients treated with bevacizumab (Levin et al.: p = 0.0013; Xu et al.: p < 0.001). Both also showed clinical improvement (Levin et al.: NA; Xu et al.: p = 0.039) and significant reduction in edema volume on both T1 gadolinium enhancement MRI (Levin et al.: p=0.0058; Xu et al.: p=0.027) and T2 FLAIR MRI (Levin et al.: p=0.0149; Xu et al.: p < 0.001). Neurocognitive improvement was significantly better after 2 months of treatment in patients receiving bevacizumab than in those given corticosteroids, as assessed by the MoCA scale (p = 0.028). The recurrence rate and side effects of the treatments showed no significant differences.

CONCLUSIONS

Patients with RBN respond to bevacizumab, which can improve clinical outcomes and cognitive function. Bevacizumab appears to be more efficacious than corticosteroid-based treatment. The safety profile was comparable to that of the corticosteroids.

The Definition and Delineation of the Target Area of Radiotherapy Based on the Recurrence Pattern of Glioblastoma After Temozolomide Chemoradiotherapy

Radiotherapy is an important treatment for glioblastoma (GBM), but there is no consensus on the target delineation for GBM radiotherapy. The Radiation Therapy Oncology Group (RTOG) and European Organisation for Research and Treatment of Cancer (EORTC) each have their own rules. Our center adopted a target volume delineation plan based on our previous studies. This study focuses on the recurrence pattern of GBM patients whose target delineations did not intentionally include the T2/fluid-attenuated inversion recovery (FLAIR) hyperintensity area outside of the gross tumor volume (GTV). We prospectively collected 162 GBM cases and retrospectively analysed the clinical data and continuous dynamic magnetic resonance images (MRI) of 55 patients with recurrent GBM. All patients received concurrent radiotherapy and chemotherapy with temozolomide (TMZ). The GTV that we defined includes the postoperative T1-weighted MRI enhancement area and resection cavity. Clinical target volume 1 (CTV1) and CTV2 were defined as GTVs with 1 and 2 cm margins, respectively. Planning target volume 1 (PTV1) and PTV2 were defined as CTV1 and CTV2 plus a 3 mm margin with prescribed doses of 60 and 54 Gy, respectively. The first recurrent contrast-enhanced T1-weighted MRI was introduced into the Varian Eclipse radiotherapy planning system and fused with the original planning computed tomography (CT) images to determine the recurrence pattern. The median follow-up time was 15.8 months. The median overall survival (OS) and progression-free survival (PFS) were 17.7 and 7.0 months, respectively. Among the patients, 44 had central recurrences, two had in-field recurrences, one had marginal recurrence occurred, 11 had distant recurrences, and three had subependymal recurrences. Five patients had multiple recurrence patterns. Compared to the EORTC protocol, target delineation that excludes the adjacent T2/FLAIR hyperintensity area reduces the brain volume exposed to high-dose radiation (P = 0.000) without an increased risk of marginal recurrence. Therefore, it is worthwhile to conduct a clinical trial investigating the feasibility of intentionally not including the T2/FLAIR hyperintensity region outside of the GTV.

Bevacizumab for radiation necrosis following radiotherapy of brain metastatic disease: a systematic review & meta-analysis

Background

Radiotherapy is the mainstay of brain metastasis (BM) management. Radiation necrosis (RN) is a serious complication of radiotherapy. Bevacizumab (BV), an anti-vascular endothelial growth factor monoclonal antibody, has been increasingly used for RN treatment. We systematically reviewed the medical literature for studies reporting the efficacy and safety of bevacizumab for treatment of RN in BM patients.

Materials and methods

PubMed, Medline, EMBASE, and Cochrane library were searched with various search keywords such as “bevacizumab” OR “anti-VEGF monoclonal antibody” AND “radiation necrosis” OR “radiation-induced brain necrosis” OR “RN” OR “RBN” AND “Brain metastases” OR “BM” until 1st Aug 2020. Studies reporting the efficacy and safety of BV treatment for BM patients with RN were retrieved. Study selection and data extraction were carried out by independent investigators. Open Meta Analyst software was used as a random effects model for meta-analysis to obtain mean reduction rates.

Results

Two prospective, seven retrospective, and three case report studies involving 89 patients with RN treated with BV were included in this systematic review and meta-analysis. In total, 83 (93%) patients had a recorded radiographic response to BV therapy, and six (6.7%) had experienced progressive disease. Seven studies (n = 73) reported mean volume reductions on gadolinium-enhanced T1 (mean: 47.03%, +/− 24.4) and T2-weighted fluid-attenuated inversion recovery (FLAIR) MRI images (mean: 61.9%, +/− 23.3). Pooling together the T1 and T2 MRI reduction rates by random effects model revealed a mean of 48.58 (95% CI: 38.32–58.85) for T1 reduction rate and 62.017 (95% CI: 52.235–71.799) for T2W imaging studies. Eighty-five patients presented with neurological symptoms. After BV treatment, nine (10%) had stable symptoms, 39 (48%) had improved, and 34 (40%) patients had complete resolution of their symptoms. Individual patient data was available for 54 patients. Dexamethasone discontinuation or reduction in dosage was observed in 30 (97%) of 31 patients who had recorded dosage before and after BV treatment. Side effects were mild.

Conclusions

Bevacizumab presents a promising treatment strategy for patients with RN and brain metastatic disease. Radiographic response and clinical improvement was observed without any serious adverse events. Further class I evidence would be required to establish a bevacizumab recommendation in this group of patients.

The individual risk of symptomatic radionecrosis after brain metastasis radiosurgery is predicted by a continuous function of the V12Gy

Introduction

Brain metastases are frequently treated with stereotactic radiosurgery (SRS). Radionecrosis (RN) is the late side effect in up to 24% of patients, being symptomatic in 8-10%. Fixed values of the radiosurgical volume receiving 12 Gy or more (V12Gy) are used to roughly predict the global risk. The aim of this retrospective study is to fine-tune the model of individual risk prediction for symptomatic radionecrosis and identify modulating factors.

Materials and methods

Data of patients treated with SRS for ≤3 BM of solid tumours at CHU-UCL-Namur were retrospectively reviewed. Doses ranging from 15 to 24 Gy were prescribed to the 70% isodose in function of the lesion diameter. Treatment was administered with a stereotactic linear accelerator. Follow-up magnetic resonance imaging was performed 3-monthly for 18 months and 6-monthly thereafter. RN was prospectively diagnosed and confirmed by the tumour board. V12Gy, previous or salvage whole-brain radiotherapy (WBRT), smoking history, diabetes, postoperative SRS, diagnosis-specific graded prognostic assessment score, cerebral lobe location and relative location (superficial versus deep) were retrieved. Univariate and multivariate analyses were performed to assess their predictive values and derive a model.

Results

128 patients with 220 lesions were analysed. The risk of RN was predicted by a continuous function of the V12Gy (p = 0.005). No other factor had a significant impact, particularly WBRT that did not increase the risk.

Conclusion

The risk of symptomatic RN is predicted on an individual basis by a model in function of the V12Gy and must be confirmed in a prospective study.

Imaging Glioblastoma Posttreatment: Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis

Radiographic monitoring of posttreatment glioblastoma is important for clinical trials and determining next steps in management. Evaluation for tumor progression is confounded by the presence of treatment-related radiographic changes, making a definitive determination less straight-forward. The purpose of this article was to describe imaging tools available for assessing treatment response in glioblastoma, as well as to highlight the definitions, pathophysiology, and imaging features typical of true progression, pseudoprogression, pseudoresponse, and radiation necrosis.

The Role of Laser Interstitial Thermal Therapy in Surgical Neuro-Oncology: Series of 100 Consecutive Patients

BACKGROUND

Laser interstitial thermal therapy (LITT) is an adjuvant treatment for intracranial lesions that are treatment refractory or in deep or eloquent brain. Initial studies of LITT in surgical neuro-oncology are limited in size and follow-up.

OBJECTIVE

To present our series of LITT in surgical neuro-oncology to better evaluate procedural safety and outcomes.

METHODS

An exploratory cohort study of all patients receiving LITT for brain tumors by a single senior neurosurgeon at a single center between 2013 and 2018. Primary outcomes included extent of ablation (EOA), time to recurrence (TTR), local control at 1-yr follow-up, and overall survival (OS). Secondary outcomes included complication rate. Outcomes were compared by tumor subtype. Predictors of outcomes were identified.

RESULTS

A total of 91 patients underwent 100 LITT procedures; 61% remain alive with 72% local control at median 7.2 mo follow-up. Median TTR and OS were 31.9 and 16.9 mo, respectively. For lesion subtypes, median TTR (months, not applicable [N/A] if <50% rate observed), local control rates at 1-yr follow-up, and median OS (months) were the following: dural-based lesions (n = 4, N/A, 75%, 20.7), metastases (n = 45, 55.9, 77.4%, 16.9), newly diagnosed glioblastoma (n = 11, 31.9, 83.3%, 32.3), recurrent glioblastoma (n = 14, 5.6, 24.3%, 7.3), radiation necrosis (n = 20, N/A, 67.2%, 16.4), and other lesions (n = 6, 12.3, 80%, 24.4). TTR differed by tumor subtype (P = .02, log-rank analysis). EOA predicted local control (P = .009, multivariate proportional hazards regression); EOA > 85% predicted longer TTR (P = .006, log-rank analysis). Complication rate was 4%.

CONCLUSION

Our series of LITT in surgical neuro-oncology, 1 of the largest to date, further evidences its safety and outcomes profile.

Management and Surveillance of Short- and Long-Term Sequelae of Radiation Therapy for the Treatment of Pediatric Brain Tumors

Radiation therapy (RT) is a mainstay for the treatment of pediatric brain tumors. As improvements in and sophistication of this modality continue to increase the survival of patients, the long-term sequelae of RT pose significant challenges in the clinical management of this patient population as they transition into adulthood. In this special edition, we review the short- and long-term effects of RT for the treatment of pediatric brain tumors and the necessary surveillance required for follow-up.

Proton Resonance Frequency Shift Thermometry: A Review of Modern Clinical Practices

Magnetic resonance imaging (MRI) has become a popular modality in guiding minimally invasive thermal therapies, due to its advanced, nonionizing, imaging capabilities and its ability to record changes in temperature. A variety of MR thermometry techniques have been developed over the years, and proton resonance frequency (PRF) shift thermometry is the current clinical gold standard to treat a variety of cancers. It is used extensively to guide hyperthermic thermal ablation techniques such as high-intensity focused ultrasound (HIFU) and laser-induced thermal therapy (LITT). Essential attributes of PRF shift thermometry include excellent linearity with temperature, good sensitivity, and independence from tissue type. This noninvasive temperature mapping method gives accurate quantitative measures of the temperature evolution inside biological tissues. In this review, the current status and new developments in the fields of MR-guided HIFU and LITT are presented with an emphasis on breast, prostate, bone, uterine, and brain treatments. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Treatment-induced brain tissue necrosis: a clinical challenge in neuro-oncology

Cancer therapy-induced adverse effects on the brain are a major challenge in neuro-oncology. Brain tissue necrosis (treatment necrosis [TN]) as a consequence of brain directed cancer therapy remains an insufficiently characterized condition with diagnostic and therapeutic difficulties and is frequently associated with significant patient morbidity. A better understanding of the underlying mechanisms, improvement of diagnostic tools, development of preventive strategies, and implementation of evidence-based therapeutic practices are pivotal to improve patient management. In this comprehensive review, we address existing challenges associated with current TN-related clinical and research practices and highlight unanswered questions and areas in need of further research with the ultimate goal to improve management of patients affected by this important neuro-oncological condition.

Computational feasibility of simulating changes in blood flow through whole-organ vascular networks from radiation injury

Vasculature is necessary to the healthy function of most tissues. In radiation therapy, injury of the vasculature can have both beneficial and detrimental effects, such as tumor starvation, cardiac fibrosis, and white-matter necrosis. These effects are caused by changes in blood flow due to the vascular injury. Previously, research has focused on simulating the radiation injury of vasculature in small volumes of tissue, ignoring the systemic effects of local damage on blood flow. Little is known about the computational feasibility of simulating the radiation injury to whole-organ vascular networks. The goal of this study was to test the computational feasibility of simulating the dose deposition to a whole-organ vascular network and the resulting change in blood flow. To do this, we developed an amorphous track-structure model to transport radiation and combined this with existing methods to model the vasculature and blood flow rates. We assessed the algorithm's computational scalability, execution time, and memory usage. The data demonstrated it is computationally feasible to calculate the radiation dose and resulting changes in blood flow from 2 million protons to a network comprising 8.5 billion blood vessels (approximately the number in the human brain) in 87 hours using a 128-node cluster. Furthermore, the algorithm demonstrated both strong and weak scalability, meaning that additional computational resources can reduce the execution time further. These results demonstrate, for the first time, that it is computationally feasible to calculate radiation dose deposition in whole-organ vascular networks. These findings provide key insights into the computational aspects of modeling whole-organ radiation damage. Modeling the effects radiation has on vasculature could prove useful in the study of radiation effects on tissues, organs, and organisms.

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases

INTRODUCTIO

Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

PATIENTS AND METHODS

We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

RESULTS

We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

CONCLUSION

SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.

Radionecrosis and cellular changes in small volume stereotactic brain radiosurgery in a porcine model

Stereotactic radiosurgery (SRS) has proven an effective tool for the treatment of brain tumors, arteriovenous malformation, and functional conditions. However, radiation-induced therapeutic effect in viable cells in functional SRS is also suggested. Evaluation of the proposed modulatory effect of irradiation on neuronal activity without causing cellular death requires the knowledge of radiation dose tolerance at very small tissue volume. Therefore, we aimed to establish a porcine model to study the effects of ultra-high radiosurgical doses in small volumes of the brain. Five minipigs received focal stereotactic radiosurgery with single large doses of 40–100 Gy to 5–7.5 mm fields in the left primary motor cortex and the right subcortical white matter, and one animal remained as unirradiated control. The animals were followed-up with serial MRI, PET scans, and histology 6 months post-radiation. We observed a dose-dependent relation of the histological and MRI changes at 6 months post-radiation. The necrotic lesions were seen in the grey matter at 100 Gy and in white matter at 60 Gy. Furthermore, small volume radiosurgery at different dose levels induced vascular, as well as neuronal cell changes and glial cell remodeling.

A Comparison of Ramipril and Bevacizumab to Mitigate Radiation-Induced Brain Necrosis: An Experimental Study

BACKGROUND

Bevacizumab, an anti-vascular endothelial growth factor (VEGF) antibody, is a new treatment approach for radionecrosis. In our study, we compared the prophylactic and therapeutic usage of a promising agent, ramipril (an angiotensin-converting enzyme inhibitor), with that of bevacizumab for reducing radiation-induced brain injury after high-dose stereotactic radiosurgery (SRS).

METHODS

A total of 60 Wistar rats were used. The rats were irradiated with a single dose of 50 Gy using a Leksell Gamma Knife device. Bevacizumab and ramipril were administered in the prophylactic protocol (starting the first day of SRS) and in the therapeutic protocol (starting the fourth week of SRS). Their usage was continued until 12 weeks, and the right frontal lobes of the rats were examined histologically (hematoxylin and eosin stain) and immunohistochemically (hypoxia-inducible factor [HIF]-1α, VEGF, and CD31 antibody expression).

RESULTS

The expression of VEGF, HIF-1α, and CD31 had significantly increased at 12 weeks after SRS compared with the control group. The addition of bevacizumab or ramipril to SRS significantly mitigated the histological severity of radiation injury and the expression of VEGF, HIF-1α, and CD31. However, the prophylactic use of bevacizumab and ramipril seemed to be more effective than therapeutic administration. Our results also revealed that the greatest benefit was achieved with the use of prophylactic administration of bevacizumab compared with other treatment protocols.

CONCLUSIONS

Ramipril might be a promising agent for patients with radionecrosis. Clinical studies are required to investigate the effective and safe doses of ramipril, which is an inexpensive, well-tolerated drug that can cross the blood-brain barrier.

A Radiomics Model for Predicting the Response to Bevacizumab in Brain Necrosis after Radiotherapy

PURPOSE

Bevacizumab is considered a promising therapy for brain necrosis after radiotherapy, while some patients fail to derive benefit or even worsen. Hence, we developed and validated a radiomics model for predicting the response to bevacizumab in patients with brain necrosis after radiotherapy.

EXPERIMENTAL DESIGN

A total of 149 patients (with 194 brain lesions; 101, 51, and 42 in the training, internal, and external validation sets, respectively) receiving bevacizumab were enrolled. In total, 1,301 radiomic features were extracted from the pretreatment MRI images of each lesion. In the training set, a radiomics signature was constructed using the least absolute shrinkage and selection operator algorithm. Multivariable logistic regression analysis was then used to develop a radiomics model incorporated in the radiomics signature and independent clinical predictors. The performance of the model was assessed by its discrimination, calibration, and clinical usefulness with internal and external validation.

RESULTS

The radiomics signature consisted of 18 selected features and showed good discrimination performance. The model, which integrates the radiomics signature, the interval between radiotherapy and diagnosis of brain necrosis, and the interval between diagnosis of brain necrosis and treatment with bevacizumab, showed favorable calibration and discrimination in the training set (AUC 0.916). These findings were confirmed in the validation sets (AUC 0.912 and 0.827, respectively). Decision curve analysis confirmed the clinical utility of the model.

CONCLUSIONS

The presented radiomics model, available as an online calculator, can serve as a user-friendly tool for individualized prediction of the response to bevacizumab in patients with brain necrosis after radiotherapy.

Outcomes and patterns of radiation associated brain image changes after proton therapy for head and neck skull base cancers

BACKGROUND AND PURPOSE

To characterize patterns and outcomes of brain MR image changes after proton therapy (PT) for skull base head and neck cancer (HNC).

MATERIAL AND METHODS

Post-treatment MRIs ≥6 months were reviewed for radiation-associated image changes (RAIC) in 127 patients. All patients had received at least a point dose of 40 Gy(RBE) to the brain. The MRIs were rigidly registered to planning CTs and RAIC lesions were contoured both on T1 weighted (post-contrast) and T2 weighted sequences, and dose-volume parameters extracted. Probability of RAIC was calculated using multistate survival analysis. Univariate/multivariate analyses were performed using Cox Regression. Recursive partitioning analysis was used to investigate dose-volume correlates of RAIC development.

RESULTS

17.3% developed RAIC. All RAIC events were asymptomatic and occurred in the temporal lobe (14), frontal lobe (6) and cerebellum (2). The median volume of the contrast enhanced RAIC lesion was 0.5 cc at their maximum size. The RAIC resolved or improved in 45.5% of the patients and were stable or progressed in 36.4%. The 3-year actuarial rate of developing RAIC was 14.3%. RAIC was observed in 63% of patients when V_{67 Gy(RBE)} of the brain ≥0.17 cc.

CONCLUSION

Small RAIC lesions after PT occurred in 17.3% of the patients; the majority in nasopharyngeal or sinonasal cancer. The estimated dose-volume correlations confirm the importance of minimizing focal high doses to brain when achievable.

Identification and Management of Progressive Enhancement After Radiation Therapy for Brain Metastases: Results from a Neurosurgical Survey

OBJECTIVE

There is a lack of consensus regarding diagnosis, timing, and method of intervention for progressive enhancement on surveillance imaging after stereotactic radiosurgery (SRS) treatment of brain metastases. We sought to characterize current practices among neurosurgeons in identifying and treating infield tumor recurrence (TR) or radiation necrosis (RN) after SRS for brain metastases.

METHODS

A voluntary survey was distributed electronically to preidentified neurosurgeons. Results were analyzed using descriptive statistics and χ² analysis.

RESULTS

A total of 120 participants completed the survey from 72 U.S. and 17 international centers. Most (69.2%) agreed that growth over ≥2 surveillance scans spaced ≥90 days apart identified irreversible progression after SRS for brain metastases. Respondents were evenly divided on the need for tissue biopsy to distinguish between TR and RN. Preferred treatment modality and time frame to initiate treatment of suspected RN differed among neurosurgeons based on SRS case volume for brain metastases (P = 0.002 and P = 0.02, respectively). Neurosurgeons who used magnetic resonance-guided laser interstitial thermal therapy (LITT) for brain metastases were more likely to prefer LITT for suspected RN, whereas those with minimal LITT experience preferred steroids (P < 0.0001). Neurosurgeons in the United States were more likely to prefer LITT for RN (37.3%) compared with international counterparts (0%).

CONCLUSIONS

Our survey of practicing neurosurgeons highlights areas of controversy in distinguishing between TR and RN and preferred management of suspected RN.

Integration of immuno-oncology with stereotactic radiosurgery in the management of brain metastases

AIM

Brain metastases traditionally carried a poor prognosis with treatment being a combination of surgery, whole-brain radiation therapy, and glucocorticoids; however, this treatment paradigm carried a significant amount of morbidity. In recent years, stereotactic radiosurgery (SRS), which involves the delivery of a highly conformal dose of radiation over a single session, has been shown to be an effective alternative to WBRT with excellent rates of local control and improved quality of life; however, a survival benefit has not been demonstrated. Recent developments have challenged the traditional view of the central nervous system being "immunologically privileged" which has led to a greater focus on treating these patients with systemic therapies. Immune checkpoint inhibitors (ICI) have been shown to improve survival in multiple malignancies. As a result, there has been increased utilization in combining these therapies in this setting.

METHODS

We conducted a literature search of medical databases (e.g. PubMed) for articles involving the use of immune checkpoint inhibitors and stereotactic radiosurgery in managing brain metastases.

RESULTS

Published evidence utilizing SRS and ICI is largely limited to single institution and retrospective in nature with the most common histology being melanoma.

CONCLUSION

Combination therapy with SRS and ICI appears to improve survival in patients with brain metastases. The available data are largely retrospective; therefore, ongoing and planned prospective studies are needed to further validate these findings.

Acute and chronic hemorrhage from radiation-induced cavernous malformation associated with late-delayed radiation necrosis in long surviving glioma patients: A case report

Although radiation therapy is a standard treatment strategy for patients with glioma, its delayed complications are not clearly understood. Radiation-induced cavernous malformation (RICM) is one of the complications in the delayed phase following radiation therapy, which usually occurs in children. Herein we present three cases of RICM with radiation necrosis in long surviving adult glioma patients, 2 with oligoastrocytoma and one with anaplastic ependymoma. Two of three patients had received an obvious overdose of radiation by additional stereotactic radiation therapy. Repeated episodes of either acute or chronic hemorrhages from RICM worsened the neurological symptoms in all cases. The interval between the last irradiation and the occurrence of symptoms was 45-173 months. The presence of hypointense rim on FLAIR or T2* on magnetic resonance imaging, which resembles the appearance of sporadic cavernous malformations, could be helpful in differentiating RICM from tumor recurrence. Surgical resection was effective in alleviating the symptoms. Microscopically, RICM is a vascular lesion with vulnerable vessels, which are observed in the center of the radiation necrosis. Repeated hemorrhages from these vessels cause either gradual or sudden worsening of neurological symptoms. Therefore, radiation overdose, which results in radiation injury, should be avoided in low grade glioma patients, who could potentially survive for a long period.

MR Perfusion and MR Spectroscopy of Brain Neoplasms

Advances in imaging techniques, such as MR perfusion and spectroscopy, are increasingly indispensable in the management and treatment plans of brain neoplasms: from diagnosing, molecular/genetic typing and grading neoplasms, augmenting biopsy results and improving accuracy, to ultimately directing and monitoring treatment and response. New developments in treatment methods have resulted in new diagnostic challenges for conventional MR imaging, such as pseudoprogression, where MR perfusion has the widest current application. MR spectroscopy is showing increasing promise in noninvasively determining genetic subtypes and, potentially, susceptibility to molecular targeted therapies.

Ultra-Low-Dose Bevacizumab For Cerebral Radiation Necrosis: A Prospective Phase II Clinical Study

OBJECTIVE

To investigate the treatment efficacy of ultra-low-dose bevacizumab for cerebral radiation necrosis.

METHODS

Patients with cerebral radiation necrosis after stereotactic radiotherapy (SRT) confirmed by imaging were included. Bevacizumab (1 mg/kg, once every three weeks, for at least three continuous treatments) was administered. The primary endpoints included change in cerebral necrosis symptoms, volume of intracranial edema, and changes in MRI signals. The secondary endpoints were adverse reactions of bevacizumab treatment.

RESULTS

In total, 21 patients were included in this study, all of whom received SRT between December 2016 and February 2019, developed cerebral radiation necrosis, and were treated with bevacizumab. Twenty patients were symptomatic from radiation necrosis, and the symptoms were alleviated in 18 patients (90%). Twenty patients had intracranial edema, and the grade of edema index (EI) was improved in 19 patients (95%). The intensity of the intracranial-enhanced MRI signals was significantly reduced in 20 patients (95.24%). The adverse reactions of bevacizumab treatment were mild, and no adverse reactions more severe than grade 2 were found.

CONCLUSION

The preliminary results showed that ultra-low-dose bevacizumab had high efficacy for treating cerebral radiation necrosis, and could be a valid alternative to the standard-dose bevacizumab.

CLINICAL REGISTRY

Chinese clinical trial registry (ChiCTR-IOD-16009803).

Brain MR findings in patients treated with particle therapy for skull base tumors

Nowadays, hadrontherapy is increasingly used for the treatment of various tumors, in particular of those resistant to conventional radiotherapy. Proton and carbon ions are characterized by physical and biological features that allow a high radiation dose to tumors, minimizing irradiation to adjacent normal tissues. For this reason, radioresistant tumors and tumors located near highly radiosensitive critical organs, such as skull base tumors, represent the best target for this kind of therapy. However, also hadrontherapy can be associated with radiation adverse effects, generally referred as acute, early-delayed and late-delayed. Among late-delayed effects, the most severe form of injury is radiation necrosis. There are various underlying mechanisms involved in the development of radiation necrosis, as well as different clinical presentations requiring specific treatments. In most cases, radiation necrosis presents as a single focal lesion, but it can be multifocal and involve a single or multiple lobes simulating brain metastasis, or it can also involve both cerebral hemispheres. In every case, radiation necrosis results always related to the extension of radiation delivery field. Multiple MRI techniques, including diffusion, perfusion imaging, and spectroscopy, are important tools for the radiologist to formulate the correct diagnosis. The aim of this paper is to illustrate the possible different radiologic patterns of radiation necrosis that can be observed in different MRI techniques in patients treated with hadrontherapy for tumors involving the skull base. The images of exemplary cases of radiation necrosis are also presented.

Conventional MRI radiomics in patients with suspected early- or pseudo-progression

Background

After radiochemotherapy, 30% of patients with early worsening MRI experience pseudoprogression (Psp) which is not distinguishable from early progression (EP). We aimed to assess the diagnostic value of radiomics in patients with suspected EP or Psp.

Methods

Radiomics features (RF) of 76 patients (53 EP and 23 Psp) retrospectively identified were extracted from conventional MRI based on four volumes-of-interest. Subjects were randomly assigned into training and validation groups. Classification model (EP versus Psp) consisted of a random forest algorithm after univariate filtering. Overall (OS) and progression-free survivals (PFS) were predicted using a semi-supervised principal component analysis, and forecasts were evaluated using C-index and integrated Brier scores (IBS).

Results

Using 11 RFs, radiomics classified patients with 75.0% and 76.0% accuracy, 81.6% and 94.1% sensitivity, 50.0% and 37.5% specificity, respectively, in training and validation phases. Addition of MGMT promoter status improved accuracy to 83% and 79.2%, and specificity to 63.6% and 75%. OS model included 14 RFs and stratified low- and high-risk patients both in the training (hazard ratio [HR], 3.63; P = .002) and the validation (HR, 3.76; P = .001) phases. Similarly, PFS model stratified patients during training (HR, 2.58; P = .005) and validation (HR, 3.58; P = .004) phases using 5 RF. OS and PFS forecasts had C-index of 0.65 and 0.69, and IBS of 0.122 and 0.147, respectively.

Conclusions

Conventional MRI radiomics has promising diagnostic value, especially when combined with MGMT promoter status, but with moderate specificity. In addition, our results suggest a potential for predicting OS and PFS.

Imaging Glioblastoma Posttreatment: Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis

Radiographic monitoring of posttreatment glioblastoma is important for clinical trials and determining next steps in management. Evaluation for tumor progression is confounded by the presence of treatment-related radiographic changes, making a definitive determination less straight-forward. The purpose of this article was to describe imaging tools available for assessing treatment response in glioblastoma, as well as to highlight the definitions, pathophysiology, and imaging features typical of true progression, pseudoprogression, pseudoresponse, and radiation necrosis.

Cerebral Radiation Necrosis: Incidence, Pathogenesis, Diagnostic Challenges, and Future Opportunities

PURPOSE OF REVIEW

Cerebral radiation necrosis (CRN) is a major dose-limiting adverse event of radiotherapy. The incidence rate of RN varies with the radiotherapy modality, total dose, dose fractionation, and the nature of the lesion being targeted. In addition to these known and controllable features, there is a stochastic component to the occurrence of CRN-the genetic profile of the host or the lesion and their role in the development of CRN.

RECENT FINDINGS

Recent studies provide some insight into the genetic mechanisms underlying radiation-induced brain injury. In addition to these incompletely understood host factors, the diagnostic criteria for CRN using structural and functional imaging are also not clear, though multiple structural and functional imaging modalities exist, a combination of which may prove to be the ideal diagnostic imaging approach. As the utilization of novel molecular therapies and immunotherapy increases, the incidence of CNR is expected to increase and its diagnosis will become more challenging. Tissue biopsies can be insensitive and suffer from sampling biases and procedural risks. Liquid biopsies represent a promising, accurate, and non-invasive diagnostic strategy, though this modality is currently in its infancy. A better understanding of the pathogenesis of CRN will expand and optimize the diagnosis and management of CRN by better utilizing existing treatment options including bevacizumab, pentoxifylline, hyperbaric oxygen therapy, and laser interstitial thermal therapy.

Management for Different Glioma Subtypes: Are All Low-Grade Gliomas Created Equal?

Following the identification of key molecular alterations that provided superior prognostication and led to the updated 2016 World Health Organization (WHO) Central Nervous System (CNS) Tumor Classification, the understanding of glioma behavior has rapidly evolved. Mutations in isocitrate dehydrogenase (IDH) 1 and 2 are present in the majority of adult grade 2 and 3 gliomas, and when used in conjunction with 1p/19q codeletion for classification, the prognostic distinction between grade 2 versus grade 3 is diminished. As such, the previously often used term of "low-grade glioma," which referred to grade 2 gliomas, has now been replaced by the phrase "lower-grade glioma" to encompass both grade 2 and 3 tumors. Additional molecular characterization is ongoing to even further classify this heterogeneous group of tumors. With such a colossal shift in the understanding of lower-grade gliomas, management of disease is being redefined in the setting of emerging molecular-genetic biomarkers. In this article, we review recent progress and future directions regarding the surgical, radiotherapeutic, chemotherapeutic, and long-term management of adult lower-grade gliomas.

Successful treatment of brain radiation necrosis resulting from triple-negative breast cancer with Endostar and short-term hyperbaric oxygen therapy: a case report

Radiation necrosis (RN) is one of the complications of radiotherapy. Angiogenesis is a key factor underlying the development of RN, and Endostar, a safe and well-tolerated recombinant human endostatin, has been used to treat a variety of tumors. Thus far, however, no definitive reports on the use of Endostar for RN treatment have been reported. Here, we report the successful treatment of one patient with symptomatic brain radiation necrosis (BRN) using Endostar in combination with short-term hyperbaric oxygen therapy (HBO). One triple-negative breast cancer patient with recurrent brain metastatic lesions after standard chemoradiotherapy was referred to a specialty center outside our hospital for stereotaxic radiotherapy. Two months later, the patient showed deteriorating clinical symptoms, and magnetic resonance imaging (MRI) showed radiation necrosis with significant surrounding edema. The patient had a poor response to mannitol and steroids. After diagnosing this patient with BRN, we began short-term HBO therapy and intravenously administered Endostar for 4 cycles. The patient responded well to this strategy, showing rapidly and dramatically improved MRI findings and clinical symptoms. No tumor progression was observed at 10 months after treatment. Endostar in combination with short-term HBO therapy had marked effects on symptomatic BRN. However, additional large-scale, double-blinded, controlled trials are necessary to confirm the clinical effect of Endostar in combination with a short-term HBO therapy regimen on BRN.

Clinical Management of Blood⁻Brain Barrier Disruptions after Active Raster-Scanned Carbon Ion Re-Radiotherapy in Patients with Recurrent Head-and-Neck Cancer

Purpose: The aim of the current evaluation was to assess central nervous system necrosis (CNSN) after re-irradiation with carbon ions (CR) in two-hundred seventeen (n = 217) patients with recurrent head-and-neck cancer (HNC). Methods: Thirty-six (n = 36) patients with CNSN were assessed retrospectively regarding clinical symptoms and radiographic response. Results: CNSN were classified according to clinical management in line with the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. At a median follow-up of 25.3 months (range 3.3–79.9 months), the median time interval until occurrence of grade I, II, and III CNSN was 9.2 months (range 2.8–75.0 months), 10.2 months (range 2.3–60.5 months), and 16.6 months (range 8.7–32.5 months), respectively. In one patient with an adenocarcinoma infiltrating the frontal lobe, an extensive CNSN grade IV was suspected but the patient declined surgical intervention. Radiographic response after treatment of CNSN grade I, II, and III, defined as ≥25% reduction of the T2 alteration on Magnetic Resonance Imaging (MRI), was observed in 4 (16.0%), 5 (29.4%), and 4 (80%) patients, respectively. Conclusion: CNSN occurred late and frequent after re-irradiation with carbon ions in patients with HNC infiltrating the base of skull. The clinical outcome with adequate treatment was encouraging but correct diagnosis of CNSN remains challenging.

The Role of Standard and Advanced Imaging for the Management of Brain Malignancies From a Radiation Oncology Standpoint

Radiation therapy (RT) plays a critical role in the overall management of many central nervous system (CNS) tumors. Advances in RT treatment planning, with techniques such as intensity modulated radiation therapy, volumetric modulated arc therapy, and stereotactic radiosurgery, now allow the delivery of highly conformal dose with great precision. These techniques rely on high-resolution 3-dimensional anatomical imaging modalities such as computed tomography or magnetic resonance imaging (MRI) scans to accurately and reliably define CNS targets and normal tissue avoidance structures. The integration of cross-sectional imaging into radiation oncology has directly translated into improvements in the therapeutic window of RT, and the union between radiation oncology and imaging is only expected to grow stronger. In addition, advanced imaging modalities including diffusion, perfusion, and spectroscopic MRIs as well as positron emission tomography (PET) scans with novel tracers are being utilized to provide additional insight into tumor biology and behavior beyond anatomy. Together, these standard and advanced imaging modalities hold significant potential to improve future RT delivery and response assessment. In this review, we will discuss the current utilization of standard/advanced imaging for CNS tumors from a radiation oncology perspective as well as the implications of novel MRI and PET modalities currently under investigation.

Longitudinal advanced MRI case report of white matter radiation necrosis

Radiation necrosis mostly occurs in and near the radiation field. We used magnetic resonance imaging to study radiation-induced necrosis of atypical onset, severity, and extent following stereotactic radiosurgery for a symptomatic arteriovenous malformation. Susceptibility-sensitive imaging, T₁-relaxation, myelin water imaging, and magnetic resonance spectroscopy were acquired three times up to 52 months postradiosurgery. Increasing water content outside the radiation field, contralateral neuronal loss, and gliosis were detected over time. Our findings suggest that radiation-induced vasculopathic changes spread more diffusely than previously described. An autoimmune response to brain antigens could underlie white matter changes outside the initial radiation field.

Antihepatotoxic benefits of Poria cocos polysaccharides on acetaminophen-lesioned livers in vivo and in vitro

In our previous study, preliminary data indicates that Poria cocos polysaccharides (PCP) shows beneficial hepatoprotection against acetaminophen (APAP)-induced liver injury in mice. However, biological molecular mechanism warrants to be further discussed. In current study, a number of biochemical tests and immunoassays were subjected to respective PCP-dosed mice in vivo and liver cells in vitro. As a result, PCP-treated mice showed reduced contents of inflammatory cytokines (tumor necrosis factor [TNF]-β and TNFsR-I), enzymological molecules (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase [LDL]), and heat shock protein 90 (Hsp90) after APAP exposure. Additionally, immunostaining assays exhibited that lowered-positive cells of cleaved-caspase-3, cleaved-poly ADP ribose polymerase, and Hsp90-labeled cells in PCP-treated livers were observed, and increased cluster of differentiation 29 (CD29), CD73-positive cells in the spleen were detected. Further, PCP-treated mouse liver cells resulted in increased cell growth, reduced LDL level. Increased proliferating cell nuclear antigen (PCNA), P38 mitogen-activated protein kinase (MAPK)-labeled cells and decreased Hsp90-positive cells in APAP-exposed liver cells were observed dose-dependently after PCP cotreatments. Collectively, our present experimental findings elucidate that PCP beneficially play hepatoprotective effects against APAP-lesioned liver cells in vivo and in vitro, potentially through the molecular mechanisms of suppressing cell death, reducing hepatocellular inflammatory stress and Hsp90 bioactivity.

Diagnosis and Management of Radiation Necrosis in Patients With Brain Metastases

The use of radiotherapy, either in the form of stereotactic radiosurgery (SRS) or whole-brain radiotherapy (WBRT), remains the cornerstone for the treatment of brain metastases (BM). As the survival of patients with BM is being prolonged, due to improved systemic therapy (i.e., for better extra-cranial control) and increased use of SRS (i.e., for improved intra-cranial control), patients are clinically manifesting late effects of radiotherapy. One of these late effects is radiation necrosis (RN). Unfortunately, symptomatic RN is notoriously hard to diagnose and manage. The features of RN overlap considerably with tumor recurrence, and misdiagnosing RN as tumor recurrence may lead to deleterious treatment which may cause detrimental effects to the patient. In this review, we will explore the pathophysiology of RN, risk factors for its development, and the strategies to evaluate and manage RN.