Late Effects of Radiation on the Central Nervous System: Role of Vascular Endothelial Damage and Glial Stem Cell Survival

Decoding Patient Heterogeneity Influencing Radiation-Induced Brain Necrosis

PURPOSE

In radiotherapy (RT) for brain tumors, patient heterogeneity masks treatment effects, complicating the prediction and mitigation of radiation-induced brain necrosis. Therefore, understanding this heterogeneity is essential for improving outcome assessments and reducing toxicity.

EXPERIMENTAL DESIGN

We developed a clinically practical pipeline to clarify the relationship between dosimetric features and outcomes by identifying key variables. We processed data from a cohort of 130 patients treated with proton therapy for brain and head and neck tumors, utilizing an expert-augmented Bayesian network to understand variable interdependencies and assess structural dependencies. Critical evaluation involved a three-level grading system for each network connection and a Markov blanket analysis to identify variables directly impacting necrosis risk. Statistical assessments included log-likelihood ratio, integrated discrimination index, net reclassification index, and receiver operating characteristic (ROC).

RESULTS

The analysis highlighted tumor location and proximity to critical structures such as white matter and ventricles as major determinants of necrosis risk. The majority of network connections were clinically supported, with quantitative measures confirming the significance of these variables in patient stratification (log-likelihood ratio = 12.17; P = 0.016; integrated discrimination index = 0.15; net reclassification index = 0.74). The ROC curve area was 0.66, emphasizing the discriminative value of nondosimetric variables.

CONCLUSIONS

Key patient variables critical to understanding brain necrosis post-RT were identified, aiding the study of dosimetric impacts and providing treatment confounders and moderators. This pipeline aims to enhance outcome assessments by revealing at-risk patients, offering a versatile tool for broader applications in RT to improve treatment personalization in different disease sites.

Mitigation of Fetal Radiation Injury from Mid-Gestation Total-body Irradiation by Maternal Administration of Mitochondrial-Targeted GS-Nitroxide JP4-039

Victims of a radiation terrorist event will include pregnant women and unborn fetuses. Mitochondrial dysfunction and oxidative stress are key pathogenic factors of fetal radiation injury. The goal of this preclinical study is to investigate the efficacy of mitigating fetal radiation injury by maternal administration of the mitochondrial-targeted gramicidin S (GS)-nitroxide radiation mitigator JP4-039. Pregnant female C57BL/6NTac mice received 3 Gy total-body irradiation (TBI) at mid-gestation embryonic day 13.5 (E13.5). Using novel time-and-motion-resolved 4D in utero magnetic resonance imaging (4D-uMRI), we found TBI caused extensive injury to the fetal brain that included cerebral hemorrhage, loss of cerebral tissue, and hydrocephalus with excessive accumulation of cerebrospinal fluid (CSF). Histopathology of the fetal mouse brain showed broken cerebral vessels and elevated apoptosis. Further use of novel 4D Oxy-wavelet MRI capable of probing in vivo mitochondrial function in intact brain revealed a significant reduction of mitochondrial function in the fetal brain after 3 Gy TBI. This was validated by ex vivo Oroboros mitochondrial respirometry. One day after TBI (E14.5) maternal administration of JP4-039, which passes through the placenta, significantly reduced fetal brain radiation injury and improved fetal brain mitochondrial respiration. Treatment also preserved cerebral brain tissue integrity and reduced cerebral hemorrhage and cell death. JP4-039 administration following irradiation resulted in increased survival of pups. These findings indicate that JP4-039 can be deployed as a safe and effective mitigator of fetal radiation injury from mid-gestational in utero ionizing radiation exposure.

Systemic Anti-Inflammatory Agents in the Prevention of Chemoradiation-Induced Mucositis: A Review of Randomised Controlled Trials

Mucositis is a pathological condition characterised by inflammation and ulceration of the mucous membranes lining the alimentary canal, particularly in the mouth (oral mucositis) and the gastrointestinal tract. It is a common side effect of cancer treatments, including chemotherapy and radiotherapy, and it is sometimes responsible for treatment interruptions. Preventing mucositis throughout the alimentary tract is therefore crucial. However, current interventions mainly target either oral or gastrointestinal side effects. This review aimed to investigate the use of systemically administered anti-inflammatory agents to prevent mucositis in cancer patients undergoing cancer treatment. PubMed, Ovid, Scopus, Web of Science, WHO ICTRP and ClinicalTrials.gov were screened to identify eligible randomised controlled trials (RCTs). The published literature on anti-inflammatory agents provides mixed evidence regarding the degree of efficacy in preventing/reducing the severity of mucositis in most anticancer treatments; however, sample size continued to be a significant limitation, alongside others discussed. Our review yielded a list of several anti-inflammatory agents that exhibit potential mucositis-preventive effects in cancer patients undergoing cancer treatment, which can be used to inform clinical practice.

Electrophysiological Changes on Laryngeal Motor Neuropathways Cause Voice Disorders for Postradiotherapy Patients with Nasopharyngeal Carcinoma

OBJECTIVE

This study explored electrophysiological changes in the laryngeal motor neuropathway and determined whether lesions in the laryngeal motor cortex (LMC) and its descending tract contribute to voice deterioration and peripheral nerve palsy in patients with nasopharyngeal carcinoma (NPC) postradiotherapy (RT).

STUDY DESIGNS

Prospective cohort study.

METHODS

Twenty-two patients with NPC at 2 to 4years post-RT (8 female and 14 male), 22 patients with NPC at 8 to 10years post-RT (8 female and 14 male), and 22 healthy individuals (9 female and 13 male) were selected to test their magnetic evoked potentials (MEP), motor nerve conduction, and voice quality using transcranial magnetic stimulation, laryngeal electromyography, and the XION DiVAS acoustic analysis software. Three groups were matched according to approximate age. Multiple comparisons were performed among the three groups.

RESULTS

The voice quality of post-RT patients with NPC deteriorated compared to that of healthy individuals. Bilateral LMC and their corticonuclear tracts to the bilateral ambiguous nuclei of post-RT patients with NPC were impaired according to multigroup comparisons of MEP amplitudes, latencies, and resting motor thresholds. The vagus and recurrent laryngeal nerves (RLN) of post-RT patients with NPC were impaired according to multigroup comparisons of the amplitude and latencies of the compound muscle action potential and latencies of f-waves.

CONCLUSIONS

The voice quality of patients with NPC deteriorated after RT. The pathogenesis of post-RT voice deterioration may involve radiation-induced injuries to the vagus, RLN, and bilateral LMC. Furthermore, radiation-induced injuries to the bilateral LMC may contribute to vagus and RLN palsies. These findings support the use of transcranial approaches to treating voice disorders and peripheral nerve palsies in post-RT patients with NPC.

TRIAL REGISTRATION

ChiCTR2100054425; Electrophysiological Study of Vocal-Fold Mobility Disorders After Radiotherapy for NPC Patients via Magnetic Evoked Potential and Their Correlation with Voice Quality Assessment; https://www.chictr.org.cn/bin/project/edit?pid=144429.

Mitigation of Fetal Irradiation Injury from Mid-Gestation Total Body Radiation with Mitochondrial-Targeted GS-Nitroxide JP4-039

Victims of a radiation terrorist event will include pregnant women and unborn fetuses. Mitochondrial dysfunction and oxidative stress are key pathogenic factors of fetal irradiation injury. The goal of this preclinical study is to investigate the efficacy of mitigating fetal irradiation injury by maternal administration of the mitochondrial-targeted gramicidin S (GS)- nitroxide radiation mitigator, JP4-039. Pregnant female C57BL/6NTac mice received 3 Gy total body ionizing irradiation (TBI) at mid-gestation embryonic day 13.5 (E13.5). Using novel time- and-motion-resolved 4D in utero magnetic resonance imaging (4D-uMRI), we found TBI caused extensive injury to the fetal brain that included cerebral hemorrhage, loss of cerebral tissue, and hydrocephalus with excessive accumulation of cerebrospinal fluid (CSF). Histopathology of the fetal mouse brain showed broken cerebral vessels and elevated apoptosis. Further use of novel 4D Oxy-wavelet MRI capable of probing in vivo mitochondrial function in intact brain revealed significant reduction of mitochondrial function in the fetal brain after 3Gy TBI. This was validated by ex vivo Oroboros mitochondrial respirometry. Maternal administration JP4-039 one day after TBI (E14.5), which can pass through the placental barrier, significantly reduced fetal brain radiation injury and improved fetal brain mitochondrial respiration. This also preserved cerebral brain tissue integrity and reduced cerebral hemorrhage and cell death. As JP4-039 administration did not change litter sizes or fetus viability, together these findings indicate JP4-039 can be deployed as a safe and effective mitigator of fetal radiation injury from mid-gestational in utero ionizing radiation exposure.

One Sentence Summary

Mitochondrial-targeted gramicidin S (GS)-nitroxide JP4-039 is safe and effective radiation mitigator for mid-gestational fetal irradiation injury.

Impact of external beam radiation on total shoulder arthroplasty outcomes: a propensity-matched cohort study

BACKGROUND

External beam radiation therapy has a number of deleterious effects on the body, and a number of post-operative complications have been reported for several surgeries including total knee arthroplasty. However, few studies have investigated the impact of external beam radiation therapy for total shoulder arthroplasty (TSA). Our study aimed to assess the systemic and joint complications associated with TSA in patients with prior radiation exposures, as well as evaluate the surgical outcomes of radiation patients compared to non-radiation TSA patients.

MATERIALS AND METHODS

A retrospective cohort analysis was conducted using the TriNetX Analytics Network. A 1:1 propensity score matching function was utilized to create two cohorts with matched baseline characteristics within the TriNetX network. Comparisons of the primary and secondary outcomes between the two cohorts were made using odds ratios. A p value of < 0.05 was determined to be significant.

RESULTS

A total of 75,510 patients that received TSA were identified with 1505 having a history of radiation therapy (RT) and 73,605 with no radiation therapy (non-RT). After propensity matching, both groups contained 1484 patients. RT patients were at higher risk for developing prosthetic joint infection, acute renal failure, altered mental state, cerebrovascular event, DVT, PE, pneumonia, respiratory failure, and UTI compared to non-RT patients at different time points (p < 0.5).

CONCLUSION

Patients with prior history of external beam radiation undergoing TSA had a higher risk of systemic complications and prosthetic joint infection compared to patients without a prior history. These complications suggest a more complicated post-operative management course for these patients.

Leukoencephalopathy in patients with brain metastases who received radiosurgery with or without whole brain radiotherapy

BACKGROUND

Whole brain radiation therapy (WBRT) for brain metastases (BMs) is a common cause of radiation-induced leukoencephalopathy; however the safety of alternative stereotactic radiosurgery (SRS) remains unclear. This study examined the incidence of leukoencephalopathy in patients treated with SRS alone versus WBRT plus SRS for BMs with a focus on the relationship between prognostic factors and leukoencephalopathy.

METHODS

Analysis was performed between 2002 and 2021. The total enrollment was 993 patients with the distribution: WBRT plus SRS (n = 291) and SRS only (n = 702). Leukoencephalopathy was graded from 0 to 3 for changes in white matter indicated by the MRI after WBRT or SRS. Patient characteristics and SRS dosimetric parameters were reviewed to identify factors that contributed to the incidence of leukoencephalopathy or overall survival.

RESULTS

The incidence of leukoencephalopathy was consistently higher in WBRT plus SRS group than in SRS alone group (p < 0.001). Leukoencephalopathy was also associated with a larger total tumor volume (≧28cm³; p = 0.028) and age (> 77 years; p = 0.025). Nonetheless, the SRS integral dose to skull in the subgroup of WBRT plus SRS treatment was not demonstrated significance in development of leukoencephalopathy (p = 0.986 for integral dose 1-2 J, p = 0.776 for integral dose > 2 J).

CONCLUSIONS

This study revealed that SRS is safe for oligo-BMs in terms of leukoencephalopathy development. Patient age and total tumor volume were identified as important factors in assessing the development of leukoencephalopathy. The additional of SRS (even at an integral dose > 2 J) did not increase the incidence of leukoencephalopathy.

Ionizing radiation, cerebrovascular disease, and consequent dementia: A review and proposed framework relevant to space radiation exposure

Space exploration requires the characterization and management or mitigation of a variety of human health risks. Exposure to space radiation is one of the main health concerns because it has the potential to increase the risk of cancer, cardiovascular disease, and both acute and late neurodegeneration. Space radiation-induced decrements to the vascular system may impact the risk for cerebrovascular disease and consequent dementia. These risks may be independent or synergistic with direct damage to central nervous system tissues. The purpose of this work is to review epidemiological and experimental data regarding the impact of low-to-moderate dose ionizing radiation on the central nervous system and the cerebrovascular system. A proposed framework outlines how space radiation-induced effects on the vasculature may increase risk for both cerebrovascular dysfunction and neural and cognitive adverse outcomes. The results of this work suggest that there are multiple processes by which ionizing radiation exposure may impact cerebrovascular function including increases in oxidative stress, neuroinflammation, endothelial cell dysfunction, arterial stiffening, atherosclerosis, and cerebral amyloid angiopathy. Cerebrovascular adverse outcomes may also promote neural and cognitive adverse outcomes. However, there are many gaps in both the human and preclinical evidence base regarding the long-term impact of ionizing radiation exposure on brain health due to heterogeneity in both exposures and outcomes. The unique composition of the space radiation environment makes the translation of the evidence base from terrestrial exposures to space exposures difficult. Additional investigation and understanding of the impact of low-to-moderate doses of ionizing radiation including high (H) atomic number (Z) and energy (E) (HZE) ions on the cerebrovascular system is needed. Furthermore, investigation of how decrements in vascular systems may contribute to development of neurodegenerative diseases in independent or synergistic pathways is important for protecting the long-term health of astronauts.

Rodent Model of Brain Radionecrosis using Clinical LINAC-based Stereotactic Radiosurgery

Purpose

Methods and Materials

Results

Conclusions

Trends in radiation dose for low grade gliomas across the United States

PURPOSE

Adjuvant radiation is often used in patients with low grade gliomas with high-risk characteristics with a recommended dose of 45-54 Gy. We used the National Cancer Database (NCDB) to see which doses were being used, and if any difference was seen in outcome.

METHODS

We queried the NCDB for patients with WHO Grade 2 primary brain tumors treated with surgery and adjuvant radiotherapy. We divided the cohort into dose groups: 45-50 Gy, 50.4-54 Gy, and > 54 Gy. Multivariable logistic regression was used to identify predictors of low and high dose radiation. Propensity matching was used to account for indication bias.

RESULTS

We identified 1437 patients meeting inclusion criteria. Median age was 45 years and 62% of patients were > 40 years old. Nearly half of patients (48%) had astrocytoma subtype and 70% had subtotal resection. The majority of patients (69%) were treated to doses between 50.4 and 54 Gy. Predictors of high dose radiation (> 54 Gy) were increased income, astrocytoma subtype, chemotherapy receipt, and treatment in later year (2014). The main predictors of survival were age > 40, astrocytoma subtype, and insurance type. Patients treated to a dose of > 54 Gy had a median survival of 73.5 months and was not reached in those treated to a lower dose (p = 0.0041).

CONCLUSIONS

This analysis shows that 50.4-54 Gy is the most widely used radiation regimen for the adjuvant treatment of low-grade gliomas. There appeared to be no benefit to higher doses, although unreported factors may impact interpretation of the results.

Mechanisms and Review of Clinical Evidence of Variations in Relative Biological Effectiveness in Proton Therapy

Proton therapy is increasingly being used as a radiation therapy modality. There is uncertainty about the biological effectiveness of protons relative to photon therapies as it depends on several physical and biological parameters. Radiation oncology currently applies a constant and generic value for the relative biological effectiveness (RBE) of 1.1, which was chosen conservatively to ensure tumor coverage. The use of a constant value has been challenged particularly when considering normal tissue constraints. Potential variations in RBE have been assessed in several published reviews but have mostly focused on data from clonogenic cell survival experiments with unclear relevance for clinical proton therapy. The goal of this review is to put in vitro findings in relation to clinical observations. Relevant in vivo pathways determining RBE for tumors and normal tissues are outlined, including not only damage to tumor cells and parenchyma but also vascular damage and immune response. Furthermore, the current clinical evidence of varying RBE is reviewed. The assessment can serve as guidance for treatment planning, personalized dose prescriptions, and outcome analysis.

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.

Sensitization of Endothelial Cells to Ionizing Radiation Exacerbates Delayed Radiation Myelopathy in Mice

Delayed radiation myelopathy is a rare, but significant late side effect from radiation therapy that can lead to paralysis. The cellular and molecular mechanisms leading to delayed radiation myelopathy are not completely understood but may be a consequence of damage to oligodendrocyte progenitor cells and vascular endothelial cells. Here, we aimed to determine the contribution of endothelial cell damage to the development of radiation-induced spinal cord injury using a genetically defined mouse model in which endothelial cells are sensitized to radiation due to loss of the tumor suppressor p53. Tie2Cre; p53FL/+ and Tie2Cre; p53FL/- mice, which lack one and both alleles of p53 in endothelial cells, respectively, were treated with focal irradiation that specifically targeted the lumbosacral region of the spinal cord. The development of hindlimb paralysis was followed for up to 18 weeks after either a 26.7 Gy or 28.4 Gy dose of radiation. During 18 weeks of follow-up, 83% and 100% of Tie2Cre; p53FL/- mice developed hindlimb paralysis after 26.7 and 28.4 Gy, respectively. In contrast, during this period only 8% of Tie2Cre; p53FL/+ mice exhibited paralysis after 28.4 Gy. In addition, 8 weeks after 28.4 Gy the irradiated spinal cord from Tie2Cre; p53FL/- mice showed a significantly higher fractional area positive for the neurological injury marker glial fibrillary acidic protein (GFAP) compared with the irradiated spinal cord from Tie2Cre; p53FL/+ mice. Together, our findings show that deletion of p53 in endothelial cells sensitizes mice to the development of delayed radiation myelopathy indicating that endothelial cells are a critical cellular target of radiation that regulates myelopathy.

Therapeutic approach of adipose-derived mesenchymal stem cells in refractory peptic ulcer

Peptic ulcer is one of the most common gastrointestinal tract disorders worldwide, associated with challenges such as refractory morbidity, bleeding, interference with use of anticoagulants, and potential side effects associated with long-term use of proton pump inhibitors. A peptic ulcer is a defect in gastric or duodenal mucosa extending from muscularis mucosa to deeper layers of the stomach wall. In most cases, ulcers respond to standard treatments. However, in some people, peptic ulcer becomes resistant to conventional treatment or recurs after initially successful therapy. Therefore, new and safe treatments, including the use of stem cells, are highly favored for these patients. Adipose-derived mesenchymal stem cells are readily available in large quantities with minimal invasive intervention, and isolation of adipose-derived mesenchymal stromal stem cells (ASC) produces large amounts of stem cells, which are essential for cell-based and restorative therapies. These cells have high flexibility and can differentiate into several types of cells in vitro. This article will investigate the effects and possible mechanisms and signaling pathways of adipose tissue-derived mesenchymal stem cells in patients with refractory peptic ulcers.

Low-Dosage Bevacizumab Treatment: Effect on Radiation Necrosis After Gamma Knife Radiosurgery for Brain Metastases

Cerebral radiation necrosis (RN), a complication of Gamma Knife radiosurgery, is difficult to treat, although bevacizumab seems to be effective. However, clinical data pertaining to bevacizumab treatment for RN are scarce, and its high price is problematic. This study explored the effectiveness of low-dose bevacizumab for RN caused by Gamma Knife. We retrospectively analyzed 22 patients who suffered cerebral RN post-Gamma Knife, and received bevacizumab treatment because of the poor efficacy of glucocorticoids. Low-dose bevacizumab (3 mg/kg) was administered for two cycles at 2-week intervals. T1- and T2-enhanced magnetic resonance imaging (MRI) images were examined for changes in RN status. We also monitored the dose of glucocorticoid, Karnofsky Performance Status (KPS) score, and adverse drug reactions. The mean volume of RN lesions decreased by 45% on T1-weighted images with contrast enhancement, and by 74% on T2-weighted images. All patients discontinued the use of glucocorticoids. According to the KPS scores, all patients showed an improvement in their symptoms and neurological function. No side effects were observed. Low-dosage bevacizumab at a dose of 3 mg/kg every 2 weeks is effective for treating cerebral RN after Gamma knife for brain metastases.

A Brief Overview of the Preclinical and Clinical Radiobiology of Microbeam Radiotherapy

Microbeam radiotherapy (MRT) is the delivery of spatially fractionated beams that have the potential to offer significant improvements in the therapeutic ratio due to the delivery of micron-sized high dose and dose rate beams. They build on longstanding clinical experience of GRID radiotherapy and more recently lattice-based approaches. Here we briefly overview the preclinical evidence for MRT efficacy and highlight the challenges for bringing this to clinical utility. The biological mechanisms underpinning MRT efficacy are still unclear, but involve vascular, bystander, stem cell and potentially immune responses. There is probably significant overlap in the mechanisms underpinning MRT responses and FLASH radiotherapy that needs to be further defined.

Functional Connectivity Density for Radiation Encephalopathy Prediction in Nasopharyngeal Carcinoma

The diagnostic efficiency of radiation encephalopathy (RE) remains heterogeneous, and prediction of RE is difficult at the pre-symptomatic stage. We aimed to analyze the whole-brain resting-state functional connectivity density (FCD) of individuals with pre-symptomatic RE using multivariate pattern analysis (MVPA) and explore its prediction efficiency. Resting data from NPC patients with nasopharyngeal carcinoma (NPC; consisting of 20 pre-symptomatic RE subjects and 26 non-RE controls) were collected in this study. We used MVPA to classify pre-symptomatic RE subjects from non-RE controls based on FCD maps. Classifier performances were evaluated by accuracy, sensitivity, specificity, and area under the characteristic operator curve. Permutation tests and leave-one-out cross-validation were applied for assessing classifier performance. MVPA was able to differentiate pre-symptomatic RE subjects from non-RE controls using global FCD as a feature, with a total accuracy of 89.13%. The temporal lobe as well as regions involved in the visual processing system, the somatosensory system, and the default mode network (DMN) revealed robust discrimination during classification. Our findings suggest a good classification efficiency of global FCD for the individual prediction of RE at a pre-symptomatic stage. Moreover, the discriminating regions may contribute to the underlying mechanisms of sensory and cognitive disturbances in RE.

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

Exposure to ionizing radiation, mechanical trauma, toxic chemicals or infections, or combinations thereof (i.e., combined injury) can induce organic injury to brain tissues, the structural disarrangement of interactive networks of neurovascular and glial cells, as well as on arrays of the paracrine and systemic destruction. This leads to subsequent decline in cognitive capacity and decompensation of mental health. There is an ongoing need for improvement in mitigating and treating radiation- or combined injury-induced brain injury. Cranial irradiation per se can cause a multifactorial encephalopathy that occurs in a radiation dose- and time-dependent manner due to differences in radiosensitivity among the various constituents of brain parenchyma and vasculature. Of particular concern are the radiosensitivity and inflammation susceptibility of: 1. the neurogenic and oligodendrogenic niches in the subependymal and hippocampal domains; and 2. the microvascular endothelium. Thus, cranial or total-body irradiation can cause a plethora of biochemical and cellular disorders in brain tissues, including: 1. decline in neurogenesis and oligodendrogenesis; 2. impairment of the blood-brain barrier; and 3. ablation of vascular capillary. These changes, along with cerebrovascular inflammation, underlie different stages of encephalopathy, from the early protracted stage to the late delayed stage. It is evident that ionizing radiation combined with other traumatic insults such as penetrating wound, burn, blast, systemic infection and chemotherapy, among others, can exacerbate the radiation sequelae (and vice versa) with increasing severity of neurogenic and microvascular patterns of radiation brain damage.

[Radiotherapy and spinal toxicity: News and perspectives]

Radiation-induced myelopathy is a devastating late effect of radiotherapy. Fortunately, this late effect is exceptional. The clinical presentation of radiation myelopathy is aspecific, typically occurring between 6 to 24 months after radiotherapy, and radiation-induced myelopathy remains a diagnosis of exclusion. Magnetic resonance imaging is the most commonly used imaging tool. Radiation oncologists must be extremely cautious to the spinal cord dose, particularly in stereotactic radiotherapy and reirradiation. Conventionally, a maximum dose of 50Gy is tolerated in normofractionated radiotherapy (1.8 to 2Gy per fraction). Repeat radiotherapies lead to consider cumulative doses above this recommendation to offer individualized reirradiation. Several factors increase the risk of radiation-induced myelopathy, such as concomitant or neurotoxic chemotherapy. The development of predictive algorithms to prevent the risk of radiation-induced myelopathy is promising. However, radiotherapy prescription should be cautious, regarding to ALARA principle (as low as reasonably achievable). As the advent of immunotherapy has improved patient survival data and the concept of oligometastatic cancer is increasing in daily practice, stereotactic treatments and reirradiations will be increasingly frequent indications. Predict the risk of radiation-induced myelopathy is therefore a major issue in the following years, and remains a daily challenge for radiation oncologists.

Stereotactic Radiosurgery for Cavernous Sinus Versus Noncavernous Sinus Dural Arteriovenous Fistulas: Outcomes and Outcome Predictors

BACKGROUND

Dural arteriovenous fistulas (DAVFs) can be categorized based on location.

OBJECTIVE

To compare stereotactic radiosurgery (SRS) outcomes between cavernous sinus (CS) and non-CS DAVFs and to identify respective outcome predictors.

METHODS

This is a retrospective study of DAVFs treated with SRS between 1988 and 2016 at 10 institutions. Patients' variables, DAVF characters, and SRS parameters were included for analyses. Favorable clinical outcome was defined as angiography-confirmed obliteration without radiological radiation-induced changes (RIC) or post-SRS hemorrhage. Other outcomes were DAVFs obliteration and adverse events (including RIC, symptomatic RIC, and post-SRS hemorrhage).

RESULTS

The overall study cohort comprised 131 patients, including 20 patients with CS DAVFs (15%) and 111 patients with non-CS DAVFs (85%). Rates of favorable clinical outcome were comparable between the 2 groups (45% vs 37%, P = .824). Obliteration rate after SRS was higher in the CS DAVFs group, even adjusted for baseline difference (OR = 4.189, P = .044). Predictors of favorable clinical outcome included higher maximum dose (P = .014) for CS DAVFs. Symptomatic improvement was associated with obliteration in non-CS DAVFs (P = .005), but symptoms improved regardless of whether obliteration was confirmed in CS DAVFs. Non-CS DAVFs patients with adverse events after SRS were more likely to be male (P = .020), multiple arterial feeding fistulas (P = .018), and lower maximum dose (P = .041).

CONCLUSION

After SRS, CS DAVFs are more likely to obliterate than non-CS ones. Because these 2 groups have different total predictors for clinical and radiologic outcomes after SRS, they should be considered as different entities.

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.

Ramipril reduces incidence and prolongates latency time of radiation-induced rat myelopathy after photon and carbon ion irradiation

To test the hypothesis that the use of an angiotensin-converting enzyme inhibitor (ACEi) during radiotherapy may be ameliorative for treatment-related normal tissue damage, a pilot study was conducted with the clinically approved (ACE) inhibitor ramipril on the outcome of radiation-induced myelopathy in the rat cervical spinal cord model. Female Sprague Dawley rats were irradiated with single doses of either carbon ions (LET 45 keV/μm) at the center of a 6 cm spread-out Bragg peak (SOBP) or 6 MeV photons. The rats were randomly distributed into 4 experimental arms: (i) photons; (ii) photons + ramipril; (iii) carbon ions and (iv) carbon ions + ramipril. Ramipril administration (2 mg/kg/day) started directly after irradiation and was maintained during the entire follow-up. Complete dose-response curves were generated for the biological endpoint radiation-induced myelopathy (paresis grade II) within an observation time of 300 days. Administration of ramipril reduced the rate of paralysis at high dose levels for photons and for the first time a similar finding for high-LET particles was demonstrated, which indicates that the effect of ramipril is independent from radiation quality. The reduced rate of myelopathy is accompanied by a general prolongation of latency time for photons and for carbon ions. Although the already clinical approved drug ramipril can be considered as a mitigator of radiation-induced normal tissue toxicity in the central nervous system, further examinations of the underlying pathological mechanisms leading to radiation-induced myelopathy are necessary to increase and sustain its mitigative effectiveness.

Radiosurgery to the spinal dorsal root ganglion induces fibrosis and inhibits satellite glial cell activation while preserving axonal neurotransmission

OBJECTIVE

Stereotactic radiosurgery (SRS) has been used to treat trigeminal neuralgia by targeting the cisternal segment of the trigeminal nerve, which in turn triggers changes in the gasserian ganglion. In the lumbar spine, the dorsal root ganglion (DRG) is responsible for transmitting pain sensitivity and is involved in the pathogenesis of peripheral neuropathic pain. Therefore, radiosurgery to the DRG might improve chronic peripheral pain. This study evaluated the clinical and histological effects of high-dose radiosurgery to the DRG in a rodent model.

METHODS

Eight Sprague-Dawley rats received either 40- or 80-Gy SRS to the fifth and sixth lumbar DRGs using the Leksell Gamma Knife Icon. Animals were euthanized 3 months after treatment, and the lumbar spine was dissected and taken for analysis. Simple histology was used to assess collagen deposition and inflammatory response. GFAP, Neu-N, substance P, and internexin were used as a measure of peripheral glial activation, neurogenesis, pain-specific neurotransmission, and neurotransmission in general, respectively. The integrity of the spinothalamic tract was assessed by means of the von Frey test.

RESULTS

The animals did not exhibit any signs of motor or sensory deficits during the experimentation period. Edema, fibrosis, and vascular sclerotic changes were present on the treated, but not the control, side. SRS reduced the expression of GFAP without affecting the expression of Neu-N, substance P, or internexin. The von Frey sensory perception elicited equivalent results for the control side and both radiosurgical doses.

CONCLUSIONS

SRS did not alter sensory or motor function but reduced the activation of satellite glial cells, a pathway for DRG-mediated pain perpetuation. Radiosurgery provoked changes equivalent to the effects of focal radiation on the trigeminal ganglion after SRS for trigeminal neuralgia, suggesting that radiosurgery could be successful in relieving radiculopathic pain.

Suitability of boric acid as a boron drug for boron neutron capture therapy for hepatoma

Hepatoma is the second leading cause of cancer death worldwide. Due to the poor outcomes of patients with late diagnosis, newer treatments for hepatoma are still needed. As an emerging therapy, boron neutron capture therapy (BNCT) may be an effective solution in hepatoma management. In this study, boric acid (BA) was used as the boron drug for in vivo analysis of action mechanism. The N1S1 single liver tumor-bearing rat and the VX2 multifocal liver tumor-bearing rabbit models were used to investigate the retention status of BA in the tumor regions during BNCT. The autoradiographic examination showed BA can localize specifically not only in the hepatoma cells but also in tumor blood vessels. Our findings indicate that superior hepatoma targeting could be achieved in BA-mediated BNCT, which supports BA to be a suitable boron drug for BNCT for hepatoma.

Fractionated carbon ion irradiations of the rat spinal cord: comparison of the relative biological effectiveness with predictions of the local effect model

Background

To determine the relative biological effectiveness (RBE) and α/β-values after fractionated carbon ion irradiations of the rat spinal cord with varying linear energy transfer (LET) to benchmark RBE-model calculations.

Material and methods

The rat spinal cord was irradiated with 6 fractions of carbon ions at 6 positions within a 6 cm spread-out Bragg-peak (SOBP, LET: 16–99 keV/μm). TD₅₀-values (dose at 50% complication probability) were determined from dose-response curves for the endpoint radiation induced myelopathy (paresis grade II) within 300 days after irradiation. Based on TD₅₀-values of 15 MV photons, RBE-values were calculated and adding previously published data, the LET and fractional dose-dependence of the RBE was used to benchmark the local effect model (LEM I and IV).

Results

At six fractions, TD₅₀-values decreased from 39.1 ± 0.4 Gy at 16 keV/μm to 17.5 ± 0.3 Gy at 99 keV/μm and the RBE increased accordingly from 1.46 ± 0.05 to 3.26 ± 0.13. Experimental α/β-ratios ranged from 6.9 ± 1.1 Gy to 44.3 ± 7.2 Gy and increased strongly with LET. Including all available data, comparison with model-predictions revealed that (i) LEM IV agrees better in the SOBP, while LEM I fits better in the entrance region, (ii) LEM IV describes the slope of the RBE within the SOBP better than LEM I, and (iii) in contrast to the strong LET-dependence, the RBE-deviations depend only weakly on fractionation within the measured range.

Conclusions

This study extends the available RBE data base to significantly lower fractional doses and performes detailed tests of the RBE-models LEM I and IV. In this comparison, LEM IV agrees better with the experimental data in the SOBP than LEM I. While this could support a model replacement in treatment planning, careful dosimetric analysis is required for the individual patient to evaluate potential clinical consequences.

Toxicity Profiles of Fractionated Radiotherapy, Contemporary Stereotactic Radiosurgery, and Transsphenoidal Surgery in Nonfunctioning Pituitary Macroadenomas

Background: Here, we compared the toxicity profiles of contemporary stereotactic radiosurgery (SRS), modern fractionated radiotherapy (FRT), and transsphenoidal surgery used to treat nonfunctioning pituitary macroadenomas. Methods: We included the data of patients with nonfunctioning pituitary macroadenomas. To compare treatment outcomes, the patients were categorized groups 1 (those receiving modern FRT), 2 (those receiving contemporary SRS), and 3 (those receiving transsphenoidal surgery). The multivariable Cox proportional hazards regression analysis was performed to yielded adjusted hazard ratios (aHRs) and their 95% CIs for local recurrence in groups 2 and 3 compared with group 1. Results: We included the data of 248 patients with nonfunctioning pituitary macroadenomas. The analytical results revealed no significant differences in second primary brain or head and neck cancer, hypopituitarism, or optic nerve injury between the three cohorts. The multivariable Cox proportional hazards regression analysis revealed that compared with group 1, the aHRs (95% CIs) for stroke risk in groups 2 and 3 were 0.37 (0.14–0.99) and 0.51 (0.31–0.84), respectively. Conclusion: Contemporary SRS and transsphenoidal surgery for nonfunctioning pituitary macroadenoma treatment have equivalent toxicity profiles. However, modern FRT for nonfunctioning pituitary macroadenoma treatment might considerably increase stroke risk.

Hyperbaric Oxygen for Radiation Necrosis of the Brain

INTRODUCTION

Hyperbaric oxygen therapy (HBOT) shows promising results in treating radionecrosis (RN) but there is limited evidence for its use in brain RN. The purpose of this study is to report the outcomes of using HBOT for symptomatic brain RN at a single institution.

METHODS

This was a retrospective review of patients with symptomatic brain RN between 2008 and 2018 and was treated with HBOT. Demographic data, steroid use, clinical response, radiologic response and toxicities were collected. The index time for analysis was the first day of HBOT. The primary endpoint was clinical improvement of a presenting symptom, including steroid dose reduction.

RESULTS

Thirteen patients who received HBOT for symptomatic RN were included. The median time from last brain radiation therapy to presenting symptoms of brain RN was 6 months. Twelve patients (92%) had clinical improvement with median time to symptom improvement of 33 days (range 1-109 days). One patient had transient improvement after HBOT but had recurrent symptomatic RN at 12 months. Of the eight patients with evaluable follow-up MRI, four patients had radiological improvement while four had stable necrosis appearance. Two patients had subsequent deterioration in MRI appearances, one each in the background of initial radiologic improvement and stability. Median survival was 15 months with median follow-up of 10 months. Seven patients reported side effects attributable to HBOT (54%), four of which were otologic in origin.

CONCLUSIONS

HBOT is a safe and effective treatment for brain RN. HBOT showed clinical and radiologic improvement or stability in most patients. Prospective studies to further evaluate the effectiveness and side effects of HBOT are needed.

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).

Neurocognitive Function in Adult Cancer Patients

Impaired neurocognitive function is an increasingly recognized morbidity in patients who have cancer. Cancer treatments, psychosocial stressors, and the malignancy itself can alter brain function. The mechanisms by which this occurs are under active investigation. Although there is a growing appreciation of its prevalence and causes, there remain limited therapeutic options for the treatment of neurocognitive dysfunction in this population. A persistent scientific and clinical effort to understand its mechanisms and impact is critical to the care of oncology patients.

Perfusion Magnetic Resonance Imaging Changes in Normal Appearing Brain Tissue after Radiotherapy in Glioblastoma Patients may Confound Longitudinal Evaluation of Treatment Response

Background

The aim of this study was assess acute and early delayed radiation-induced changes in normal-appearing brain tissue perfusion as measured with perfusion magnetic resonance imaging (MRI) and the dependence of these changes on the fractionated radiotherapy (FRT) dose level.

Patients and methods

Seventeen patients with glioma WHO grade III-IV treated with FRT were included in this prospective study, seven were excluded because of inconsistent FRT protocol or missing examinations. Dynamic susceptibility contrast MRI and contrast-enhanced 3D-T1-weighted (3D-T1w) images were acquired prior to and in average (standard deviation): 3.1 (3.3), 34.4 (9.5) and 103.3 (12.9) days after FRT. Pre-FRT 3D-T1w images were segmented into white- and grey matter. Cerebral blood volume (CBV) and cerebral blood flow (CBF) maps were calculated and co-registered patient-wise to pre-FRT 3D-T1w images. Seven radiation dose regions were created for each tissue type: 0-5 Gy, 5-10 Gy, 10-20 Gy, 20-30 Gy, 30-40 Gy, 40-50 Gy and 50-60 Gy. Mean CBV and CBF were calculated in each dose region and normalised (nCBV and nCBF) to the mean CBV and CBF in 0-5 Gy white- and grey matter reference regions, respectively.

Results

Regional and global nCBV and nCBF in white- and grey matter decreased after FRT, followed by a tendency to recover. The response of nCBV and nCBF was dose-dependent in white matter but not in grey matter.

Conclusions

Our data suggest that radiation-induced perfusion changes occur in normal-appearing brain tissue after FRT. This can cause an overestimation of relative tumour perfusion using dynamic susceptibility contrast MRI, and can thus confound tumour treatment evaluation.

Prophylactic Bevacizumab May Mitigate Radiation Injury: An Experimental Study

BACKGROUND

Stereotactic radiosurgery (SRS) is widely used to treat brain pathologies alone or in concert with other treatment modalities. However, there are some side effects, such as radiation injury characterized by edema and necrosis in peripheral tissues, that must be managed. A new treatment agent against this side effect is bevacizumab, which targets increased vascular endothelial growth factor (VEGF) as a prominent etiologic factor in radiation injury. In this study, we created a rat experimental model to describe the effects of both radiation and the anti-VEGF monoclonal antibody bevacizumab following high-dose SRS, and to compare the effects of prophylactic and delayed-onset bevacizumab treatment.

METHODS

Fifty-four adult male Wistar rats were allocated into 9 groups based on differing Gamma-knife surgery (GKS) doses and bevacizumab treatment protocols. After 12 weeks, the rats' right frontal lobes were examined with hematoxylin and eosin staining and immunohistochemistry analysis via VEGF and CD31 antibodies.

RESULTS

Radiation necrosis occurred to varying degrees in all irradiated animals between 3 and 10 weeks post-SRS. Higher GKS dose (50% isodose of 100 Gy) led earlier necrosis and prophylaxis of bevacizumab at this dose was associated with delayed onset of necrosis. Moreover, prophylactic bevacizumab mitigated the effects of radiation necrosis following GKS at both doses, whereas this effect was not prominent with late initiation of bevacizumab (treatment protocol).

CONCLUSIONS

Our findings show that the onset and degree of radiation injury are affected by the GKS dose and protocol of bevacizumab administration.

Radiation-Induced Myelitis: Initial and Follow-Up MRI and Clinical Features in Patients at a Single Tertiary Care Institution during 20 Years

Myelitis is a rare complication of radiation exposure to the spinal cord and is often a diagnosis of exclusion. A retrospective review of clinical records and serial imaging was performed to identify subjects with documented myelitis and a history of prior radiation. Eleven patients fulfilled the inclusion criteria. All patients had longitudinally extensive cord involvement with homogeneous precontrast T1 hyperintense signal in the adjacent vertebrae, corresponding to the radiation field. T2 signal abnormalities involving the central two-thirds of the cord were seen in 6/11 patients (55%). The degree of cord expansion and contrast enhancement was variable but was seen in 6 (54%) and 5 (45%) patients, respectively. On follow-up, 2 patients developed cord atrophy, while complete resolution was noted in 1. Clinical improvement was noted in 5 patients, with symptom progression in 2 patients. Our results suggest that radiation myelitis is neither universally progressive nor permanent, and some radiographic and clinical improvement may occur.

Bevacizumab Monotherapy Reduces Radiation-induced Brain Necrosis in Nasopharyngeal Carcinoma Patients: A Randomized Controlled Trial

PURPOSE

Studies have shown that addition of bevacizumab to corticosteroids improves outcome against radiation-induced brain necrosis (RN). Here, we aimed to evaluate the effectiveness and safety of bevacizumab monotherapy on RN in nasopharyngeal carcinoma (NPC) patients.

METHODS AND MATERIALS

In this multicenter open-label study, patients with RN were randomly assigned (1:1) into a bevacizumab group (5 mg/kg intravenously every 2 weeks, for 4 cycles) or a corticosteroid group (methylprednisolone 500 mg/day intravenously for 3 consecutive days and then gradually tapered, followed by 10 mg/day oral prednisone, for 2 months in total). Magnetic resonance imaging (MRI) was performed pre- and post-treatment to define the radiographic response. The primary outcome was a 2-month response rate as determined by MRI and clinical symptoms. All of the patients were followed up with for 6 months. The trial was registered at www.clinicaltrials.gov (NCT01621880).

RESULTS

Of 121 patients screened, 112 patients met the entry criteria. Thirty-eight (65.5%) patients in the bevacizumab group showed response, which was significantly higher than that in the corticosteroid group (65.5% vs 31.5%, P < .001). The mean percentage decrease in RN volume seen on T1 post-gadolinium and T2-weighted fluid-attenuated inversion recovery (FLAIR) MRI was 25.5% and 51.8%, respectively, in the bevacizumab group, versus 5.0% and 19.3%, respectively, in the corticosteroid group. Moreover, 36 patients (62.1%) on bevacizumab and 23 patients (42.6%) on corticosteroids demonstrated clinical improvement (P = .039). During the 6-month follow up, fourteen patients on bevacizumab and 13 patients on corticosteroids showed RN recurrence. The most frequent adverse event in the bevacizumab group was hypertension (20.6%).

CONCLUSIONS

Our study indicate that compared with corticosteroids, bevacizumab offers improved symptomatic relief and radiographic response.

Long-Term Outcomes After Stereotactic Radiosurgery for Spine Metastases: Radiation Dose-Response for Late Toxicity

PURPOSE

To document the 5- and 10-year rates of late toxicity and vertebral compression fracture (VCF) in long-term survivors after stereotactic radiosurgery for spine metastases.

METHODS AND MATERIALS

A retrospective review was performed on 562 patients treated with SRS for spine metastases between April 2001 and July 2011. Selecting those with at least 5-year survival after SRS, included were 43 patients who collectively underwent 84 treatments at 54 spine sites. Most were treated with single-fraction stereotactic radiosurgery to a median dose of 16 Gy (range, 12-24 Gy), and 56% of sites had received prior external beam radiation therapy. Late toxicities and VCFs occurring in the absence of tumor progression were recorded. Binary logistic regression was used to identify predictors of late complications.

RESULTS

Nine patients (17% of treatment sites) developed grade ≥2 late toxicities at a median time of 12.8 months (range, 4.2-59.0 months). Actuarial 5- and 10-year rates of grade ≥2 late toxicity were 17% and 17%, respectively. On multivariate analysis, only cumulative biologically effective dose (BED₃) > 200 Gy (or EQD2_2Gy [2-Gy equivalent dose calculated using an α/β ratio of 2] > 130 Gy) was associated with grade ≥2 late toxicity (P = .036). Maximum point BED₃ > 110 Gy (or EQD2_2Gy > 70 Gy) to spinal cord or cauda equina was associated with grade ≥2 late neuropathy (P = .017). Nine VCFs (18%) occurred at a median time of 10.2 months (range, 3.2-57.2 months), with 5- and 10-year VCF rates of 17% and 17%, respectively.

CONCLUSION

Stereotactic radiosurgery for primary treatment and reirradiation of spinal metastases is associated with a moderate risk of late toxicity with 10-year follow-up. Risk of late toxicity significantly increases with cumulative BED₃ > 200 Gy and spinal cord or cauda equina point BED₃ > 110 Gy. Patients remain at moderate risk of VCF up to 5 years after treatment, with a plateau in incidence thereafter up to 10 years.

Exploration of the recurrence in radiation brain necrosis after bevacizumab discontinuation

Objective: The aim of the paper was to investigate the recurrence and its causes of radiation brain necrosis following bevacizumab discontinuation. Methods: This study included 14 patients with radiation brain necrosis (confirmed through imaging) after stereotactic radiotherapy for a primary or metastatic brain tumor and who received bevacizumab treatment from June 2011 through December 2014. The patients received bevacizumab at 5 mg/kg, q3-4w, for at least 3 cycles. The T1 signal intensity from enhanced MRI images was used as the evaluation criteria for the brain necrosis treatment efficacy. Results: brain necrosis improved in 13 of the 14 cases (92.9%). However, during follow-up, 10 of the 13 responsive patients (76.9%) exhibited a recurrence in brain necrosis, and a multiple linear regression analysis shows that brain necrosis recurrence was related to the follow-up time after the initial bevacizumab treatment discontinuation. Conclusion: bevacizumab produced good short-term effects for radiation brain necrosis; however, most of the patients would recurrence after bevacizumab is discontinued. Thus, brain necrosis was irreversible.

Late normal tissue response in the rat spinal cord after carbon ion irradiation

Background

The present work summarizes the research activities on radiation-induced late effects in the rat spinal cord carried out within the “clinical research group ion beam therapy” funded by the German Research Foundation (DFG, KFO 214).

Methods and materials

Dose–response curves for the endpoint radiation-induced myelopathy were determined at 6 different positions (LET 16–99 keV/μm) within a 6 cm spread-out Bragg peak using either 1, 2 or 6 fractions of carbon ions. Based on the tolerance dose TD₅₀ of carbon ions and photons, the relative biological effectiveness (RBE) was determined and compared with predictions of the local effect model (LEM I and IV). Within a longitudinal magnetic resonance imaging (MRI)-based study the temporal development of radiation-induced changes in the spinal cord was characterized. To test the protective potential of the ACE (angiotensin converting enzyme)-inhibitor ramipril™, an additional dose–response experiment was performed.

Results

The RBE-values increased with LET and the increase was found to be larger for smaller fractional doses. Benchmarking the RBE-values as predicted by LEM I and LEM IV with the measured data revealed that LEM IV is more accurate in the high-LET, while LEM I is more accurate in the low-LET region. Characterization of the temporal development of radiation-induced changes with MRI demonstrated a shorter latency time for carbon ions, reflected on the histological level by an increased vessel perforation after carbon ion as compared to photon irradiations. For the ACE-inhibitor ramipril™, a mitigative rather than protective effect was found.

Conclusions

This comprehensive study established a large and consistent RBE data base for late effects in the rat spinal cord after carbon ion irradiation which will be further extended in ongoing studies. Using MRI, an extensive characterization of the temporal development of radiation-induced alterations was obtained. The reduced latency time for carbon ions is expected to originate from a dynamic interaction of various complex pathological processes. A dominant observation after carbon ion irradiation was an increase in vessel perforation preferentially in the white matter. To enable a targeted pharmacological intervention more details of the molecular pathways, responsible for the development of radiation-induced myelopathy are required.

[Cognitive deficits following brain tumor radiation therapy]

Brain radiation is an important treatment option for malignant and benign brain diseases. The possible acute or chronic impact of radiation therapy on cognitive performance is important for daily functioning and quality of life. A detailed evaluation of cognitive impairment is important in the context of how to control disease progression. The susceptibility of the hippocampus to radiation-induced neuronal damage and its important role in memory highlight that therapeutic strategies require precision medicine.

[Repair and time-dose factor: The example of spinal cord irradiation]

The question whether a reirradiation is possible, with either curative of palliative intent, is a frequent issue and a true therapeutic challenge, in particular for a critical organ sensitive to cumulative dose, such as the spinal cord. Preclinical experimental data, based on debatable models that are hardly transferable to patients, suggest that there is a possibility of reirradiation, beyond the classical threshold for dose constraints, taking into account the "time-dose factor". Although the underlying biological mechanisms are however uncertain, scarce clinical data seem to confirm that the tolerance of spinal cord to reirradiation does exist, provided that a particular attention to total dose is given. In the context where modern stereotactic irradiation facilities expand therapeutic perspectives, we review the literature on possibilities of reirradiation, through the example of spinal cord reirradiation.

Radiation-induced brain injury: low-hanging fruit for neuroregeneration

Brain radiation is a fundamental tool in neurooncology to improve local tumor control, but it leads to profound and progressive impairments in cognitive function. Increased attention to quality of life in neurooncology has accelerated efforts to understand and ameliorate radiation-induced cognitive sequelae. Such progress has coincided with a new understanding of the role of CNS progenitor cell populations in normal cognition and in their potential utility for the treatment of neurological diseases. The irradiated brain exhibits a host of biochemical and cellular derangements, including loss of endogenous neurogenesis, demyelination, and ablation of endogenous oligodendrocyte progenitor cells. These changes, in combination with a state of chronic neuroinflammation, underlie impairments in memory, attention, executive function, and acquisition of motor and language skills. Animal models of radiation-induced brain injury have demonstrated a robust capacity of both neural stem cells and oligodendrocyte progenitor cells to restore cognitive function after brain irradiation, likely through a combination of cell replacement and trophic effects. Oligodendrocyte progenitor cells exhibit a remarkable capacity to migrate, integrate, and functionally remyelinate damaged white matter tracts in a variety of preclinical models. The authors here critically address the opportunities and challenges in translating regenerative cell therapies from rodents to humans. Although valiant attempts to translate neuroprotective therapies in recent decades have almost uniformly failed, the authors make the case that harnessing human radiation-induced brain injury as a scientific tool represents a unique opportunity to both successfully translate a neuroregenerative therapy and to acquire tools to facilitate future restorative therapies for human traumatic and degenerative diseases of the central nervous system.

Management of Cerebral Radiation Necrosis: A Retrospective Study of 12 Patients

BACKGROUND

Cerebral radiation necrosis (RN) is a severe complication of radiotherapy for cerebral pathologies. This study discusses the radiographic and pathological features of 12 patients with RN and investigates the management strategy.

METHODS

Eleven patients with brain tumors, and one with cerebral cavernous angioma, treated by surgical resection or Gamma Knife alone before radiotherapy developed RN during follow-up. Surgical resection for the cerebral RN was performed in nine patients, and the other three patients received medical treatment. The clinical features, magnetic resonance imaging (MRI), surgical findings, and pathological sections are reviewed.

RESULTS

The diagnosis of RN was confirmed by histological study in all the patients; those with surgical and medical treatment recovered.

CONCLUSION

As a major complication of radiotherapy, from the clinical and neuroradiological points of view, RN may simulate tumor recurrence. Due to the increasing number of patients with RN who will need to be treated in future years, the definite diagnosis and appropriate treatment of RN remain critical.

Analysis of risk and predictors of brain radiation necrosis after radiosurgery

In this study, we examined the factors contributing to brain radiation necrosis and its predictors of patients treated with Cyberknife radiosurgery. A total of 94 patients with primary or metastatic brain tumours having been treated with Cyberknife radiotherapy from Sep. 2006 to Oct. 2011 were collected and retrospectively analyzed. Skull based tracking was used to deliver radiation to 104 target sites. and the prescribed radiation doses ranged from 1200 to 4500 cGy in 1 to 8 fractions with a 60% to 87% isodose line. Radiation necrosis was confirmed by imaging or pathological examination. Associations between cerebral radiation necrosis and factors including diabetes, cardio-cerebrovascular disease, target volume, isodose line, prescribed dosage, number of fractions, combination with whole brain radiation and biologically equivalent dose (BED) were determined by logistic regression. ROC curves were created to measure the predictive accuracy of influence factors and identify the threshold for brain radiation necrosis. Our results showed that radiation necrosis occurred in 12 targets (11.54%). Brain radiation necrosis was associated by BED, combination with whole brain radiotherapy, and fractions (areas under the ROC curves = 0.892±0.0335, 0.650±0.0717, and 0.712±0.0637 respectively). Among these factors, only BED had the capability to predict brain radiation necrosis, and the threshold dose was 7410 cGy. In conclusion, BED is the most effective predictor of brain radiation necrosis, with a dose of 7410 cGy being identified as the threshold.

Stereotactic radiotherapy following surgery for brain metastasis: Predictive factors for local control and radionecrosis

PURPOSE

To evaluate local control and adverse effects after postoperative hypofractionated stereotactic radiosurgery in patients with brain metastasis.

METHODS

We reviewed patients who had hypofractionated stereotactic radiosurgery (7.7Gy×3 prescribed to the 70% isodose line, with 2mm planning target volume margin) following resection from March 2008 to January 2014. The primary endpoint was local failure defined as recurrence within the surgical cavity. Secondary endpoints were distant failure rates and the occurrence of radionecrosis.

RESULTS

Out of 95 patients, 39.2% had metastatic lesions from a non-small cell lung cancer primary tumour. The median Graded Prognostic Assessment score was 3 (48% of patients). One-year local control rates were 84%. Factors associated with improved local control were no cavity enhancement on pre-radiation MRI (P<0.00001), planning target volume less than 12cm³ (P=0.005), Graded Prognostic Assessment score 2 or above (P=0.009). One-year distant cerebral control rates were 56%. Thirty-three percent of patients received whole brain radiation therapy. Histologically proven radionecrosis of brain tissue occurred in 7.2% of cases. The size of the preoperative lesion and the volume of healthy brain tissue receiving 21Gy (V₂₁) were both predictive of the incidence of radionecrosis (P=0.010 and 0.036, respectively).

CONCLUSION

Adjuvant hypofractionated stereotactic radiosurgery to the postoperative cavity in patients with brain metastases results in excellent local control in selected patients, helps delay the use of whole brain radiation, and is associated with a relatively low risk of radionecrosis.