Radiation-Induced Large Vessel Cerebral Vasculopathy in Pediatric Patients With Brain Tumors Treated With Proton Radiation Therapy

Evolving Role of Proton Radiation Therapy in Clinical Practice

With the expansion of proton radiation therapy centers across the United States and a gradually expanding body of academic evidence supporting its use, more patients are receiving-and asking about-proton therapy than ever before. Here, we outline, for nonradiation oncologists, the theoretical benefits of proton therapy, the clinical evidence to date, the controversies affecting utilization, and the numerous randomized trials currently in progress. We also discuss the challenges of researching and delivering proton therapy, including the cost of constructing and maintaining centers, barriers with insurance approval, clinical situations in which proton therapy may be approached with caution, and the issue of equitable access for all patients. The purpose of this review is to assist practicing oncologists in understanding the evolving role of proton therapy and to help nonradiation oncologists guide patients regarding this technology.

Vascular complications in craniopharyngioma-resected paediatric patients: a single-center experience

Background

Craniopharyngioma (CP), although slow growing and histologically benign, has high morbidity, mostly related to hypothalamus-pituitary dysfunction and electrolyte imbalance. Increased risk of vascular complications has been described. However, data are still poor, especially in the paediatric population. The aim of our study was to evaluate the occurrence, timing, and predisposing factors of deep venous thrombosis (DVT) and other vascular alterations in neurosurgical paediatric CP patients.

Materials and Methods

In a single-centre, retrospective study, we investigated 19 CP patients (11 males, 8 females, mean age 10.5 ± 4.3 years), who underwent neurosurgery between December 2016 and August 2022, referred to Meyer Children's Hospital IRCCS in Florence.

Results

Five patients (26.3%) presented vascular events, which all occurred in connection with sodium imbalances. Three DVT (two with associated pulmonary embolism, in one case leading to death) developed in the post-operative period, most frequently at 7-10 days. Elevated D-dimers, a reduced partial activated thrombin time and a prolonged C-reactive protein increase were highly related to thrombotic vascular events. One case of posterior cerebral artery pseudoaneurysm was described soon after neurosurgery, requiring vascular stenting. Superficial vein thrombophlebitis was a late complication in one patient with other predisposing factors.

Conclusion

CP patients undergoing neurosurgery are at risk of developing DVT and vascular alterations, thus careful follow-up is mandatory. In our study, we found that the phase of transition from central diabetes insipidus to a syndrome of inappropriate antidiuretic hormone secretion may be a period of significant risk for DVT occurrence. Careful vascular follow-up is mandatory in CP-operated patients.

Review of Cerebral Radiotherapy-Induced Vasculopathy in Pediatric and Adult Patients

Radiation therapy (RT) causes radiation-induced vasculopathy, which requires clinicians to identify and manage this side effect in pediatric and adult patients. This article reviews previous findings about the pathophysiology of RT-induced vascular injury, including endothelial cell injury, oxidative stress, inflammatory cytokines, angiogenic pathways, and remodeling. The vasculopathy is categorized into ischemic vasculopathy, hemorrhagic vasculopathy, carotid artery injury, and other malformations (cavernous malformations and aneurysms) in populations of pediatric and adult patients separately. The prevention and management of this RT-induced side effect are also discussed. The article summarizes the distribution and risk factors of different types of RT-induced vasculopathy. This will help clinicians identify high-risk patients with corresponding vasculopathy subtypes to deduce prevention and treatment strategies accordingly.

The incidence of radiation-induced moyamoya among pediatric brain tumor patients who received photon radiation versus those who received proton beam therapy: a systematic review

Cranial irradiation is associated with several adverse events such as endocrinopathy, growth retardation, neurocognitive impairment, secondary malignancies, cerebral vasculopathy, and potential stroke. The better side effects profile of proton beam therapy compared with that of photon radiation therapy is due to its physical properties, mainly the sharp dose fall-off after energy deposition in the Bragg peak. Despite the better toxicity profile of proton beam therapy, the risk of  moyamoya syndrome still exists. We conducted a systematic review of the existing literature on moyamoya syndrome after receiving cranial radiation therapy for pediatric brain tumors to investigate the incidence of moyamoya syndrome after receiving photon versus proton radiation therapy. In this review, we report that the incidence of moyamoya syndrome after receiving proton beam therapy is almost double that of photon-induced moyamoya syndrome. Patients who received proton beam therapy for the management of pediatric brain tumors are more likely to develop moyamoya syndrome at the age of less than 5 years. Meanwhile, most patients with proton-induced moyamoya are more likely to be diagnosed within the first 2 years after the completion of their proton beam therapy.

Case report of intracranial large vessel occlusion in glioblastoma multiforme patient after radiation therapy

INTRODUCTION

Vasculopathy of the large arteries is a prominent complication of radiotherapy. Radiation-induced cerebral vasculopathy can cause arterial stenosis/occlusion, cerebral hemorrhage, and aneurysm formation. We report a cases of glioblastoma multiforme (GBM) with occlusive radiation vasculopathy (ORV).

CASE PRESENTATION

This 28-year-old patient who suffered from GBM had surgery for cytoreduction and received postoperative CCRT. We adopted the radiotherapy and oncology group radiation guideline. This patient had cerebrovascular accident episodes without any known risk. Therefore, ORV was highly suspected and vascular stenosis was confirmed using magnetic resonance angiography (MRA) or digital subtraction angiography. Extracranial-intracranial bypass was performed and patency was confirmed. The patient had not suffered from recurrent symptoms of transient ischemic attack or ischemic stroke for 1.5 years.

DISCUSSION

This is the first article to report bypass surgery for GBM patients. Although the median survival rate of GBM is approximately 15 months, the short survival time may be sufficient for occlusive vasculopathy to occur. Regular follow-up magnetic resonance imaging assessments are recommended, as is MRA as a screening tool for the early diagnosis of ORV.The Stenting versus Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial focused on atherosclerotic intracranial arterial stenosis, revealing that aggressive medical management was superior to stenting for secondary stroke prevention; however, it did not mention radiation-induced vasculopathy. Bypass surgery has yielded some positive outcomes. In the absence of contraindications, antiplatelet or anticoagulation agents could be added, and bypass surgery could be performed because there was no stent in the distal intracranial arteries.

CONCLUSION

MRA is a potential screening tool for ORV in GBM patients and bypass surgery could be performed to improve brain perfusion. Bypass surgery could help patient with occlusive radiation vasculopathy.

Late Radiation-Induced Carotid Artery Stenosis and Stroke in Pediatric Patient Treated With Proton Radiation Therapy for Skull-Base Chordoma

Radiation vasculopathy is a well-recognized late complication of radiation therapy. We present a case of a stroke 29 years after high-dose proton radiation therapy for skull-base chordoma due to occlusion of bilateral internal carotid arteries.

Tissue Reactions and Mechanism in Cardiovascular Diseases Induced by Radiation

The long-term survival rate of cancer patients has been increasing as a result of advances in treatments and precise medical management. The evidence has accumulated that the incidence and mortality of non-cancer diseases have increased along with the increase in survival time and long-term survival rate of cancer patients after radiotherapy. The risk of cardiovascular disease as a radiation late effect of tissue damage reactions is becoming a critical challenge and attracts great concern. Epidemiological research and clinical trials have clearly shown the close association between the development of cardiovascular disease in long-term cancer survivors and radiation exposure. Experimental biological data also strongly supports the above statement. Cardiovascular diseases can occur decades post-irradiation, and from initiation and development to illness, there is a complicated process, including direct and indirect damage of endothelial cells by radiation, acute vasculitis with neutrophil invasion, endothelial dysfunction, altered permeability, tissue reactions, capillary-like network loss, and activation of coagulator mechanisms, fibrosis, and atherosclerosis. We summarize the most recent literature on the tissue reactions and mechanisms that contribute to the development of radiation-induced cardiovascular diseases (RICVD) and provide biological knowledge for building preventative strategies.

Radiation and the nervous system

Radiation therapy is widely used for benign and malignant brain tumours as it is effective and well tolerated. However, damage to the surrounding healthy nervous system tissue leads to a variety of complications both in the short term and long term, ranging from mild and self-limiting to irreversible and fatal. Radiation neurotoxicity is due to a combination of early inflammation and oligodendroglial damage followed later by brain tissue necrosis, white matter damage, accelerated vascular disease and the development of secondary tumours. This article explains the basic principles of radiation physics, the different modalities used in clinical practice, how radiotherapy is planned and delivered and the scientific basis of radiation damage. The main body of the article focuses on the clinical features of radiation toxicity in the brain, spinal cord, cranial and peripheral nerves with an emphasis on the distinction between early and delayed complications.

Risk of secondary malignant neoplasms in children following proton therapy vs. photon therapy for primary CNS tumors: A systematic review and meta-analysis

Background

Central nervous system tumors are now the most common primary neoplasms seen in children, and radiation therapy is a key component in management. Secondary malignant neoplasms (SMNs) are rare, but dreaded complications. Proton beam therapy (PBT) can potentially minimize the risk of SMNs compared to conventional photon radiation therapy (RT), and multiple recent studies with mature data have reported the risk of SMNs after PBT. We performed this systematic review and meta-analysis to characterize and compare the incidence of SMNs after proton and photon-based radiation for pediatric CNS tumors.

Methods

A systematic search of literature on electronic (PubMed, Cochrane Central, and Embase) databases was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. We included studies reporting the incidence and nature of SMNs in pediatric patients with primary CNS tumors. The crude incidence of SMNs and all secondary neoplasms were separately extracted, and the random-effects model was used for pooled analysis and subgroup comparison was performed between studies using photons vs. protons.

Results

Twenty-four studies were included for analysis. A total of 418 SMNs were seen in 38,163 patients. The most common SMN were gliomas (40.6%) followed by meningiomas (38.7%), sarcomas (4.8%), and thyroid cancers (4.2%). The median follow-up was 8.8 years [3.3–23.2].The median latency to SMN for photons and protons were 11.9 years [5-23] and 5.9 years [5-6.7], respectively. The pooled incidence of SMNs was 1.8% (95% CI: 1.1%–2.6%, I² = 94%) with photons and 1.5% (95% CI: 0%–4.5%, I² = 81%) with protons. The pooled incidence of all SNs was not different [photons: 3.6% (95% CI: 2.5%–4.8%, I² = 96%) vs. protons: 1.5% (95% CI: 0–4.5%, I² = 80%); p = 0.21].

Conclusion

We observed similar rates of SMN with PBT at 1.5% compared to 1.8% with photon-based RT for pediatric CNS tumors. We observed a shorter latency to SMN with PBT compared to RT. With increasing use of pencil beam scanning PBT and VMAT, further studies are warranted to evaluate the risk of secondary cancers in patients treated with these newer modalities.

Image-based data mining applies to data collected from children

PURPOSE

Image-based data mining (IBDM) is a novel voxel-based method for analyzing radiation dose responses that has been successfully applied in adult data. Because anatomic variability and side effects of interest differ for children compared to adults, we investigated the feasibility of IBDM for pediatric analyses.

METHODS

We tested IBDM with CT images and dose distributions collected from 167 children (aged 10 months to 20 years) who received proton radiotherapy for primary brain tumors. We used data from four reference patients to assess IBDM sensitivity to reference selection. We quantified spatial-normalization accuracy via contour distances and deviations of the centers-of-mass of brain substructures. We performed dose comparisons with simplified and modified clinical dose distributions with a simulated effect, assessing their accuracy via sensitivity, positive predictive value (PPV) and Dice similarity coefficient (DSC).

RESULTS

Spatial normalizations and dose comparisons were insensitive to reference selection. Normalization discrepancies were small (average contour distance < 2.5 mm, average center-of-mass deviation < 6 mm). Dose comparisons identified differences (p < 0.01) in 81% of simplified and all modified clinical dose distributions. The DSCs for simplified doses were high (peak frequency magnitudes of 0.9-1.0). However, the PPVs and DSCs were low (maximum 0.3 and 0.4, respectively) in the modified clinical tests.

CONCLUSIONS

IBDM is feasible for childhood late-effects research. Our findings may inform cohort selection in future studies of pediatric radiotherapy dose responses and facilitate treatment planning to reduce treatment-related toxicities and improve quality of life among childhood cancer survivors.

Recent Updates on Radiation Therapy for Pediatric Optic Pathway Glioma

Optic pathway glioma (OPG) is a rare tumor located in optic nerve, optic tract, or optic chiasm. Treatment options for OPG include surgery, radiation therapy (RT), and chemotherapy. Although RT may provide favorable long-term outcomes in manner of either adjuvant or salvage aim, chemotherapy-first approach is increasingly performed due to possible late effects of RT. Proton beam RT may allow normal tissue sparing of radiation exposure compared to conventional X-ray treatment. Therefore, proton beam RT is expected to reduce complications from RT. This review discusses the recent updates on oncologic outcomes of OPG, late toxicities following RT, and compares the outcomes between X-ray treatment and proton beam RT.

Review: Neurological Complications From Therapies for Pediatric Brain Tumors

Surgery, chemotherapy and radiation have been the mainstay of pediatric brain tumor treatment over the past decades. Recently, new treatment modalities have emerged for the management of pediatric brain tumors. These therapies range from novel radiotherapy techniques and targeted immunotherapies to checkpoint inhibitors and T cell transfer therapies. These treatments are currently investigated with the goal of improving survival and decreasing morbidity. However, compared to traditional therapies, these novel modalities are not as well elucidated and similarly has the potential to cause significant short and long-term sequelae, impacting quality of life. Treatment complications are commonly mediated through direct drug toxicity or vascular, infectious, or autoimmune mechanisms, ranging from immune effector cell associated neurotoxicity syndrome with CART-cells to neuropathy with checkpoint inhibitors. Addressing treatment-induced complications is the focus of new trials, specifically improving neurocognitive outcomes. The aim of this review is to explore the pathophysiology underlying treatment related neurologic side effects, highlight associated complications, and describe the future direction of brain tumor protocols. Increasing awareness of these neurologic complications from novel therapies underscores the need for quality-of-life metrics and considerations in clinical trials to decrease associated treatment-induced morbidity.

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.

Delineation atlas of the Circle of Willis and the large intracranial arteries for evaluation of doses to neurovascular structures in pediatric brain tumor patients treated with radiation therapy

BACKGROUND

Survivors of pediatric brain tumors are susceptible to neurovascular disease after radiotherapy, with dose to the chiasm or Circle of Willis (CW) as risk factors. The aims of this study were to develop a delineation atlas of neurovascular structures, to investigate the doses to these structures in relation to tumor location and to investigate potential dose surrogates for the CW dose.

MATERIAL AND METHODS

An atlas of the CW, the large intracranial arteries and the suprasellar cistern (SC) was developed and validated. Thirty proton plans from previously treated pediatric brain tumor patients were retrieved and grouped according to tumor site: 10 central, 10 lateralized, and 10 posterior fossa tumors. Based on the atlas, neurovascular structures were delineated and dose metrics (mean dose (D_mean) and maximal dose (D_max)) to these structures and the already delineated chiasm were evaluated. The agreement between dose metrics to the CW vs. chiasm/SC was investigated. The minimal Hausdorff distance (HD_min) between the target and SC was correlated with the SC D_mean.

RESULTS

The median D_mean/D_max to the CW were 53 Gy(RBE)/55 Gy(RBE) in the central tumors, 18 Gy(RBE)/25 Gy(RBE) in the lateralized tumors and 30 Gy(RBE)/49 Gy(RBE) in the posterior fossa tumors. There was a good agreement between the D_max/D_mean to the CW and the SC for all cases (R²=0.99), while in the posterior fossa group, the CW D_max was underestimated when using the chiasm as surrogate (R²=0.76). Across all patients, cases with HD_min < 10 mm between the target and the SC received the highest SC D_mean.

CONCLUSION

The pattern of dose to neurovascular structures varied with the tumor location. For all locations, SC doses could be used as a surrogate for CW doses. A minimal distance larger than 10 mm between the target and the SC indicated a potential for neurovascular dose sparing.

Neuroblastoma

The survival of patients with high-risk neuroblastoma has improved significantly with the use of intensive multimodality treatment regimens, including chemotherapy, surgery, radiation therapy, myeloablative chemotherapy followed by stem cell rescue, and immunotherapy. This report summarizes the current treatment strategies used in the COG and SIOP for children with neuroblastoma. The improved global collaboration and the adoption of a uniform International Neuroblastoma Risk Group Staging System will help facilitate comparison of homogeneous pretreatment cohorts across clinical trials. Future research strategies regarding the indications for and dosages of radiation therapy to the primary and metastatic sites, and the integration of meta-iodobenzyl guanidine therapy into the multimodal treatment program, are discussed.

Topographic variability of the normal circle of Willis anatomy on a paediatric population

Long-term sequelae are major limitations of radiation therapy use, especially for childhood brain tumour. Circle of Willis irradiation strongly increases the long-term risk of stroke, but to establish dose-response relationship, anticipating long-term effects of new techniques, requires to perform accurate and reproducible dosimetric estimations in large cohorts of patients having received radiotherapy decades ago. For the accuracy of retrospective dose reconstruction, the topographic variability of the Circle of Willis arteries is crucial. In order to improve retrospective dosimetric studies and dose-volume estimates to the typical Circle of Willis arteries, we aim to study the inter-individual topographic variability of these structures. Thirty-eight time of flight MRI sequences of children aged 2–17 years in both genders were investigated. A region growth algorithm was used for the segmentation of the cerebral arteries. A rigid registration in a common skull was performed following the anatomy of skull base foramina. The Posterior clinoid processes of the sella turcica were used as reference landmark (R0), and 5 key landmarks were chosen in each segmented Circle of Willis, then distances between the 5 landmarks and R0 were calculated for each of the 38 subjects. The distance between R0 and each landmark of the Circle of Willis followed a normal distribution, the average values ranging from 13.6 to 17.0 mm, and the standard deviations ranged from 2.6 to 3.0 mm, i.e. less than a fifth of the average value. The perimeter of the Circle of Willis was longer in older subjects, this increase being isotropic. Our study shows a remarkably low topographic variability of the typical Circle of Willis. An important result, allowing reliable anthropomorphic phantoms-based retrospective estimations of the radiation doses delivered to these arterial structures during radiotherapy treatment.

Spectrum of neuroimaging findings post-proton beam therapy in a large pediatric cohort

PURPOSE

Proton beam therapy (PBT) is now well established for the treatment of certain pediatric brain tumors. The intrinsic properties of PBT are known to reduce long-term negative effects of photon radiotherapy (PRT). To better understand the intracranial effects of PBT, we analyzed the longitudinal imaging changes in a cohort of children with brain tumors treated by PBT with clinical and radiotherapy dose correlations.

MATERIALS AND METHODS

Retrospective imaging review of 46 patients from our hospital with brain tumors treated by PBT. The imaging findings were correlated with clinical and dose parameters.

RESULTS

Imaging changes were assessed by reviewing serial magnetic resonance imaging (MRI) scans following PBT over a follow-up period ranging from 1 month to 7 years. Imaging changes were observed in 23 patients undergoing PBT and categorized as pseudoprogression (10 patients, 43%), white matter changes (6 patients, 23%), parenchymal atrophy (6 patients, 23%), and cerebral large vessel arteriopathy (5 patients, 25%). Three patients had more than one type of imaging change. Clinical symptoms attributable to PBT were observed in 13 (28%) patients.

CONCLUSION

In accordance with published literature, we found evidence of varied intracranial imaging changes in pediatric brain tumor patients treated with PBT. There was a higher incidence (10%) of large vessel cerebral arteriopathy in our cohort than previously described in the literature. Twenty-eight percent of patients had clinical sequelae as a result of these changes, particularly in the large vessel arteriopathy subgroup, arguing the need for angiographic and perfusion surveillance to pre-empt any morbidities and offer potential neuro-protection.

Recognizing Radiation-induced Changes in the Central Nervous System: Where to Look and What to Look For

Radiation therapy (RT) continues to play a central role as an effective therapeutic modality for a variety of tumors and vascular malformations in the central nervous system. Although the planning and delivery techniques of RT have evolved substantially during the past few decades, the structures surrounding the target lesion are inevitably exposed to radiation. A wide variety of radiation-induced changes may be observed at posttreatment imaging, which may be confusing when interpreting images. Histopathologically, radiation can have deleterious effects on the vascular endothelial cells as well as on neuroglial cells and their precursors. In addition, radiation induces oxidative stress and inflammation, leading to a cycle of further cellular toxic effects and tissue damage. On the basis of the time of expression, radiation-induced injury can be divided into three phases: acute, early delayed, and late delayed. Acute and early delayed injuries are usually transient and reversible, whereas late delayed injuries are generally irreversible. The authors provide a comprehensive review of the timeline and expected imaging appearances after RT, including the characteristic imaging features after RT with concomitant chemotherapy. Specific topics discussed are imaging features that help distinguish expected posttreatment changes from recurrent disease, followed by a discussion on the role of advanced imaging techniques. Knowledge of the RT plan, the amount of normal structures included, the location of the target lesion, and the amount of time elapsed since RT is highly important at follow-up imaging, and the reporting radiologist should be able to recognize the characteristic imaging features after RT and differentiate these findings from tumor recurrence. ^©RSNA, 2020.

Systematic review of the incidence and risk factors for cerebral vasculopathy and stroke after cranial proton and photon radiation for childhood brain tumors

Background

The aim of our study is to determine the incidence, timing, and risk factors for cerebral vasculopathy after cranial proton and photon radiation for pediatric brain tumors.

Methods

We performed a single-institution retrospective review of a cohort of children treated with proton radiation for brain tumors. MRA and/or MRI were reviewed for evidence of cerebral vascular stenosis and infarcts. Twenty-one similar studies (17 photon, 4 proton) were identified by systematic literature review.

Results

For 81 patients with median follow-up of 3 years, the rates of overall and severe vasculopathy were 9.9% and 6.2% respectively, occurring a median of 2 years post radiation. Dose to optic chiasm greater than 45 Gy and suprasellar location were significant risk factors. Results were consistent with 4 prior proton studies (752 patients) that reported incidence of 5% to 6.7%, 1.5 to 3 years post radiation. With significantly longer follow-up (3.7-19 years), 9 studies (1108 patients) with traditional photon radiation reported a higher rate (6.3%-20%) and longer time to vasculopathy (2-28 years). Significant risk factors were neurofibromatosis type 1 (NF-1; rate 7.6%-60%) and suprasellar tumors (9%-20%). In 10 studies with photon radiation (1708 patients), the stroke rate was 2% to 18.8% (2.3-24 years post radiation).

Conclusions

Childhood brain tumor survivors need screening for vasculopathy after cranial radiation, especially with higher dose to optic chiasm, NF-1, and suprasellar tumors. Prospective studies are needed to identify risk groups, and ideal modality and timing, for screening of this toxicity.

Pencil beam scanning proton therapy for the treatment of craniopharyngioma complicated with radiation-induced cerebral vasculopathies: A dosimetric and linear energy transfer (LET) evaluation

BACKGROUND AND PURPOSE

This study analyses the dosimetric and dose averaged Linear Energy transfer (LETd) correlation in paediatric craniopharyngioma (CP) patients with and without radiation-induced cerebral vasculopathies (RICVs) treated with pencil beam scanning (PBS) proton therapy (PT).

MATERIAL AND METHODS

We reviewed a series of 16 CP patients treated with PT to a median dose of 54 Gy(RBE). Two (12.5%) index patients presented RICVs 14 and 24 months (median, 19) after PT. Organs at risks (OARs) as bilateral internal carotid arteries (ICAs) and circle of Willis were contoured based on CTs and MRIs pre- and post-PT. Dosimetry was reviewed and LETd distributions were calculated; LETd metric for PTVs and OARs were analysed. For a sub-cohort, dosimetric and LETd values robustness due to range uncertainties were computed.

RESULTS

For the two index patients, no correlation was observed between RICVs and OARs doses. However for those patients mean(maximum) LETd values in the affected OARs were up to 4.0 ± 0.4 (7.8 ± 0.1)keV/μm; those LETd values were significantly higher (p = 0.02) than the mean(maximum) LETd values for the rest of the cohort (mean: 3.1 ± 0.3, maximum: 4.8 ± 1.0 keV/μm). This was due to asymmetric field arrangement, thus resulting in marked asymmetric LETd distributions. For such arrangement, maximum LETd values variations in vascular structures due to range uncertainties were up to 1.2 keV/μm, whilst for the symmetric one they were up to 0.7 keV/μm.

CONCLUSIONS

For children with and without RICVs, quantitative analysis showed a significant correlation with LETd average/maximum values in vascular structures, whilst no correlation was found on dosimetric parameters.

Radiation-induced accelerated aging of the brain vasculature in young adult survivors of childhood brain tumors

Background

Cranial radiotherapy may damage the cerebral vasculature. The aim of this study was to understand the prevalence and risk factors of cerebrovascular disease (CVD) and white matter hyperintensities (WMHs) in childhood brain tumors (CBT) survivors treated with radiotherapy.

Methods

Seventy CBT survivors who received radiotherapy were enrolled in a cross-sectional study at a median 20 years after radiotherapy cessation. The prevalence of and risk factors for CVD were investigated using MRI, MRA, and laboratory testing. Tumors, their treatment, and stroke-related data were retrieved from patients’ files.

Results

Forty-four individuals (63%) had CVD at a median age of 27 years (range, 16-43 years). The prevalence rates at 20 years for CVD, small-vessel disease, and large-vessel disease were 52%, 38%, and 16%, respectively. Ischemic infarcts were diagnosed in 6 survivors, and cerebral hemorrhage in 2. Lacunar infarcts were present in 7, periventricular or deep WMHs in 34 (49%), and mineralizing microangiopathy in 21 (30%) survivors. Multiple pathologies were detected in 44% of the participants, and most lesions were located in a high-dose radiation area. Higher blood pressure was associated with CVD and a presence of WMHs. Higher cholesterol levels increased the risk of ischemic infarcts and WMHs, and lower levels of high-density lipoprotein and higher waist circumference increased the risk of lacunar infarcts.

Conclusions

Treating CBTs with radiotherapy increases the risk of early CVD and WMHs in young adult survivors. These results suggest an urgent need for investigating CVD prevention in CBT patients.

Vascular complications in pediatric craniopharyngioma patients: a case-based update

PURPOSE

Craniopharyngiomas remain a challenging entity for neurosurgeons because of their deep-seated, midline location, and intimate relationship with critical neurovascular structures. With high long-term survival rates, patients with craniopharyngioma are likely to experience significant late morbidity related to both disease and therapy.

METHOD AND RESULTS

In this paper, we present two cases of late vascular complications after multi-modal treatment of craniopharyngioma.

CONCLUSION

Available data suggests that pediatric patients with craniopharyngioma represent a particularly vulnerable group.

Evaluation and treatment of children with radiation-induced cerebral vasculopathy

OBJECTIVE

Stenoocclusive cerebral vasculopathy is an infrequent delayed complication of ionizing radiation. It has been well described with photon-based radiation therapy but less so following proton-beam radiotherapy. The authors report their recent institutional experience in evaluating and treating children with radiation-induced cerebral vasculopathy.

METHODS

Eligible patients were age 21 years or younger who had a history of cranial radiation and subsequently developed vascular narrowing detected by MR arteriography that was significant enough to warrant cerebral angiography, with or without ischemic symptoms. The study period was January 2011 to March 2019.

RESULTS

Thirty-one patients met the study inclusion criteria. Their median age was 12 years, and 18 (58%) were male. Proton-beam radiation therapy was used in 20 patients (64.5%) and photon-based radiation therapy was used in 11 patients (35.5%). Patients were most commonly referred for workup as a result of incidental findings on surveillance tumor imaging (n = 23; 74.2%). Proton-beam patients had a shorter median time from radiotherapy to catheter angiography (24.1 months [IQR 16.8-35.4 months]) than patients who underwent photon-based radiation therapy (48.2 months [IQR 26.6-61.1 months]; p = 0.04). Eighteen hemispheres were revascularized in 15 patients. One surgical patient suffered a contralateral hemispheric infarct 2 weeks after revascularization; no child treated medically (aspirin) has had a stroke to date. The median follow-up duration was 29.2 months (IQR 21.8-54.0 months) from the date of the first catheter angiogram to last clinic visit.

CONCLUSIONS

All children who receive cranial radiation therapy from any source, particularly if the parasellar region was involved and the child was young at the time of treatment, require close surveillance for the development of vasculopathy. A structured and detailed evaluation is necessary to determine optimal treatment.

Occlusive radiation cerebral vasculopathy implies medical complexity: a case report

Background

Cranial irradiation is one of the main treatment modalities for central nervous system tumors. It carries many complications, one being occlusive radiation vasculopathy of large vessels. It is an underrecognized etiology for stroke, especially in the younger population. The pathophysiological process is controversial, but there is much literature supporting the theory of its being a secondary form of moyamoya disease.

Case presentation

A 31-year-old Caucasian man with a history of pineal blastoma at the age of 3 years, which was treated with resection, radiotherapy, and chemotherapy, presented to our institution with right M1 stroke. Further assessment by computed tomographic perfusion study with acetazolamide demonstrated steal phenomenon of the right middle cerebral artery territory (type III response) with a small internal region of matched cerebral blood volume defect (that is, infarct core). Coincidentally, he was found to have multiple brain masses consistent with meningiomas. Occlusive radiation vasculopathy was the most likely culprit of the patient’s stroke. The patient was treated medically with “baby” acetylsalicylic acid and clopidogrel for 3 months, then continued only on baby acetylsalicylic acid.

Conclusion

Late-onset occlusive radiation vasculopathy is a potentially severe iatrogenic manifestation of radiotherapy that requires a high index of suspicion as an etiology of stroke in young population, especially those with coexistent meningioma that might be a strong indicator for occlusive radiation vasculopathy as the stroke culprit. We reviewed the available literature to better understand the pathogenesis, clinical presentation, and treatment options of occlusive radiation vasculopathy. Applying perfusion studies with acetazolamide measures the cerebrovascular reserve in patients with occlusive radiation vasculopathy, which could help in determining the appropriate available treatment option.

Selective Neural Deletion of the Atg7 Gene Reduces Irradiation-Induced Cerebellar White Matter Injury in the Juvenile Mouse Brain by Ameliorating Oligodendrocyte Progenitor Cell Loss

Radiotherapy is an effective tool for treating brain tumors, but irradiation-induced toxicity to the normal brain tissue remains a major problem. Here, we investigated if selective neural autophagy related gene 7 (Atg7) deletion has a persistent effect on irradiation-induced juvenile mouse brain injury. Ten-day-old Atg7 knockout under a nestin promoter (KO) mice and wild-type (WT) littermates were subjected to a single dose of 6 Gy whole-brain irradiation. Cerebellar volume, cell proliferation, microglia activation, inflammation, and myelination were evaluated in the cerebellum at 5 days after irradiation. We found that neural Atg7 deficiency partially prevented myelin disruption compared to the WT mice after irradiation, as indicated by myelin basic protein staining. Irradiation induced oligodendrocyte progenitor cell (OPC) loss in the white matter of the cerebellum, and Atg7 deficiency partly prevented this. The mRNA expression of oligodendrocyte and myelination-related genes (Olig2, Cldn11, CNP, and MBP) was higher in the cerebellum in Atg7 KO mice compared with WT littermates. The total cerebellar volume was significantly reduced after irradiation in both Atg7 KO and WT mice. Atg7-deficient cerebellums were in a regenerative state before irradiation, as judged by the increased OPC-related and neurogenesis-related transcripts and the increased numbers of microglia; however, except for the OPC parameters these were the same in both genotypes after irradiation. Finally, there was no significant change in the number of astrocytes in the cerebellum after irradiation. These results suggest that selective neural Atg7 deficiency reduces irradiation-induced cerebellar white matter injury in the juvenile mouse brain, secondary to prevention of OPC loss.

Current status of proton therapy outcome for paediatric cancers of the central nervous system - Analysis of the published literature

INTRODUCTION

The most common solid tumours that develop in children are cancers of the central nervous system. Due to the increased rate of survival over the past decades, greater focus has been placed on the minimisation of long term side effects. In childhood cancer survivors, over 60% report one or more radiation-related late toxicities while half of these adverse events are graded as life-threatening or severe. Proton therapy enables high conformity with the planning target volume and a reduction in dose to areas beyond the target. Owing to the unique nature of dose delivery with proton therapy a reduction of low doses to normal tissues is achievable, and is believed to allow for a decrease in long-term treatment-related side effects. This paper aims to review the published literature around the effectiveness of proton therapy for the treatment of paediatric cancers of the central nervous system, with a focus on treatment outcomes and treatment-related toxicities.

METHODS

A search strategy utilising the Medline database was created with the intent of including all articles reporting on proton therapy, paediatric cancers, CNS tumours and treatment outcomes. The final search strategy included the following limitations: limited to humans, English, published from 2000 onwards. The final article count total was 74.

RESULTS AND CONCLUSIONS

Proton therapy for the treatment of paediatric cancers of the central nervous system was found to provide survival and tumour control outcomes comparable to photon therapy. Reduced incidence of severe acute and late toxicities was also reported with the use of proton therapy. This includes reduced severity of endocrine, neurological, IQ and QoL deficits. Currently, extensive follow-up of proton patient populations still needs to be made to determine incidences of late-onset toxicities and secondary malignancies. Current evidence surrounding proton therapy use in paediatric patients supports its effectiveness and potential benefits in reducing the incidence of severe toxicities in later life.

Imaging findings in radiation therapy complications of the central nervous system

Radiation therapy is a useful treatment for tumors and vascular malformations of the central nervous system. Radiation therapy is associated with complications, including leukoencephalopathy, radiation necrosis, vasculopathy, and optic neuropathy. Secondary tumors are also often seen long after radiation therapy. Secondary tumors are often benign tumors, such as hemangiomas and meningiomas, but sometimes malignant gliomas and soft tissue sarcomas emerge. We review the imaging findings of complications that may occur after brain radiation therapy.

An Integrative Survival Analysis with Identification of Prognostic Factors in the Patients with Coexisting Glioma and Intracranial Aneurysm

OBJECTIVE

This study aimed to perform an integrative clinical and survival analysis for patients with coexisting glioma and intracranial aneurysm and to assess the influence of prognostic factors on overall survival (OS).

METHODS

A systematic literature search on PubMed and Web of Science was performed for literature in English published from 1951 to August 2017. Detailed information including clinical characteristics, treatments, critical events, and time to events for survival analysis was extracted from the included articles. Clinical characteristics of included patients were reviewed, and survival analysis was performed to identify prognostic factors of OS.

RESULTS

A total of 56 cases from 38 articles published in English-language journals were included in this study, and relative details were selected for integrative analysis. Univariate analysis demonstrated that age (<47/≥47 years), ruptured aneurysm (yes/no), glioma type (glioblastoma multiforme [GBM]/no GBM), World Health Organization (WHO) grade (low/high), and radiotherapy (yes/no) had a statistically significant correlation with OS (log-rank P = 0.004, P = 0.037, P = 0.004, P < 0.001, and P < 0.001, respectively). Further, multivariate analysis revealed that WHO grade (hazard ratio [HR], 22.383; 95% confidence interval [CI], 1.795-279.151; P = 0.016) and receiving radiotherapy (HR, 0.054; 95% CI, 0.009-0.333; P = 0.002) were the independent prognostic factors for OS.

CONCLUSIONS

This integrative survival analysis revealed that WHO grade and receiving radiotherapy were independent prognostic factors for OS, and patients with low-grade glioma and receiving radiotherapy had longer survival than counter groups. Nevertheless, similar clinical studies which should be larger samples, multicenter, and collaborative are needed further.