Effects of Radiation on Cerebral Vasculature: A Review:

Diffusion and Perfusion MRI Predicts Response Preceding and Shortly After Radiosurgery to Brain Metastases: A Pilot Study

BACKGROUND AND PURPOSE

To determine the ability of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to predict long-term response of brain metastases prior to and within 72 hours of stereotactic radiosurgery (SRS).

METHODS

In this prospective pilot study, multiple b-value DWI and T1-weighted DCE-MRI were performed in patients with brain metastases before and within 72 hours following SRS. Diffusion-weighted images were analyzed using the monoexponential and intravoxel incoherent motion (IVIM) models. DCE-MRI data were analyzed using the extended Tofts pharmacokinetic model. The parameters obtained with these methods were correlated with brain metastasis outcomes according to modified Response Assessment in Neuro-Oncology Brain Metastases criteria.

RESULTS

We included 25 lesions from 16 patients; 16 patients underwent pre-SRS MRI and 12 of 16 patients underwent both pre- and early (within 72 hours) post-SRS MRI. The perfusion fraction (f) derived from IVIM early post-SRS was higher in lesions demonstrating progressive disease than in lesions demonstrating stable disease, partial response, or complete response (q = .041). Pre-SRS extracellular extravascular volume fraction, v_e , and volume transfer coefficient, K^trans , derived from DCE-MRI were higher in nonresponders versus responders (q = .041).

CONCLUSIONS

Quantitative DWI and DCE-MRI are feasible imaging methods in the pre- and early (within 72 hours) post-SRS evaluation of brain metastases. DWI- and DCE-MRI-derived parameters demonstrated physiologic changes (tumor cellularity and vascularity) and offer potentially useful biomarkers that can predict treatment response. This allows for initiation of alternate therapies within an effective time window that may help prevent disease progression.

Ruptured de novo Aneurysm following Gamma Knife Surgery for Arteriovenous Malformation: Case Report

Stereotactic radiosurgery is a well-known treatment tool for arteriovenous malformations (AVMs). The method has high validity and minimal invasiveness, but late-onset problems involving tumor formation and vasculopathy induced by radiation have been reported. We present a rare case of a radiation-induced ruptured de novo aneurysm following Gamma Knife surgery (GKS) for an AVM. A 17-year-old, right-handed male underwent GKS for AVM at the left parietal lobe. After 3 years, a follow-up angiogram showed a residual AVM at the angular gyrus. Then, a 2nd GKS was performed for the residual lesion. Six years after the 1st GKS, the AVM disappeared on the angiogram. Seven years later, he suffered a sudden onset of headache. A left carotid angiogram revealed a ruptured aneurysm at the M2-M3 junction of the middle cerebral artery parietal branch. Coil embolization was performed, and the aneurysm was occluded. The patient was discharged without any neurologic deficits.

Bypass surgery to treat symptomatic fusiform dilation of the internal carotid artery following craniopharyngioma resection: report of 2 cases

Fusiform dilation of the internal carotid artery (FDICA) is an infrequent vascular complication following resection of suprasellar lesions in the pediatric population, and its course appears to be benign without apparent clinical symptoms. However, data correlating symptomatic FDICA with bypass surgery are scarce. The authors here report 2 symptomatic cases that were treated using internal maxillary artery bypass more than 5 years after total removal of a craniopharyngioma at an outside institution. Both cases of FDICA were resected to relieve the mass effect and to expose the craniopharyngioma. The postoperative course was uneventful, and radiological imaging revealed graft conduit patency. To the authors' knowledge, this is the first reported use of extracranial to intracranial bypass to treat FDICA following removal of a suprasellar lesion. Their findings suggest that bypass surgery is a useful therapeutic approach for symptomatic cases of FDICA and total removal of recurrent craniopharyngioma. Moreover, the indications for surgical intervention and treatment modalities are discussed in the context of previous relevant cases.

Flow Induced Microvascular Network Formation of Therapeutic Relevant Arteriovenous (AV) Loop-Based Constructs in Response to Ionizing Radiation

BACKGROUND The arteriovenous (AV) loop model enables axial vascularization to gain a functional microcirculatory system in tissue engineering constructs in vivo. These constructs might replace surgical flaps for the treatment of complex wounds in the future. Today, free flaps are often exposed to high-dose radiation after defect coverage, according to guideline-oriented treatment plans. Vascular response of AV loop-based constructs has not been evaluated after radiation, although it is of particular importance. It is further unclear whether the interposed venous AV loop graft is crucial for the induction of angiogenesis. MATERIAL AND METHODS We exposed the grafted vein to a single radiation dose of 2 Gy prior to loop construction to alter intrinsic and angio-inductive properties specifically within the graft. Vessel loops were embedded in a fibrin-filled chamber for 15 days and radiation-induced effects on flow-mediated vascularization were assessed by micro-CT and two-dimensional histological analysis. RESULTS Vessel amount was significantly impaired when an irradiated vein graft was used for AV loop construction. However, vessel growth and differentiation were still present. In contrast to vessel density, which was homogeneously diminished in constructs containing irradiated veins, vessel diameter was primarily decreased in the more peripheral regions. CONCLUSIONS Vascular luminal sprouts were significantly diminished in irradiated venous grafts, suggesting that the interposing vein constitutes a vital part of the AV loop model and is essential to initiate flow-mediate angiogenesis. These results add to the current understanding of AV loop-based neovascularization and suggest clinical implications for patients requiring combined AV loop-based tissue transfer and adjuvant radiotherapy.

Cardiovascular Complications of Cranial and Neck Radiation

OPINION STATEMENT

Cancer survivors who receive head and neck radiation are at increased risk for cerebrovascular events. This is mediated via damage to the hypothalamus-pituitary axis leading to the metabolic syndrome and extracranial arterial injury leading to carotid artery stenosis. Head and neck radiation can also lead to intracranial injury that can present as moyamoya, especially in children. Survivors require lifelong periodic follow-up for the development of pan-hypopituitarism or its individual components as well as for dyslipidemia and obesity. Aggressive control of traditional cardiovascular risk factors is recommended to reduce cardiovascular morbidity and mortality. There are no specific guidelines for the surveillance and management of asymptomatic carotid artery disease in cancer survivors. However, regular detailed examination for carotid bruits and neurological symptoms is recommended. Treatment of significant radiation-induced carotid artery disease has not been specifically studied and is based upon recommendations for patients with atherosclerotic carotid stenosis. Carotid endarterectomy can be difficult in radiation patients due to anatomic concerns and the risk of post-operative cranial nerve injury and wound complications but should be considered in patients with suitable anatomy and neck architecture. Carotid artery stenting, while successful, may be associated with greater long-term mortality and neurologic complications. Regardless of the strategy employed, radiation patients are at increased risk for restenosis and should undergo routine surveillance even after revascularization.

Angiographic, hemodynamic, and histological changes in an animal model of brain arteriovenous malformations treated with Gamma Knife radiosurgery

OBJECT

Brain arteriovenous malformations (AVMs) are a major cause of stroke. Many AVMs are effectively obliterated by stereotactic radiosurgery, but such treatment for lesions larger than 3 cm is not as effective. Understanding the responses to radiosurgery may lead to new biological enhancements to this treatment modality. The aim of the present study was to investigate the hemodynamic, morphological, and histological effects of Gamma Knife surgery (GKS) in an animal model of brain AVM.

METHODS

An arteriovenous fistula was created by anastomosing the left external jugular vein to the side of the common carotid artery in 64 male Sprague-Dawley rats (weight 345 ± 8.8 g). Six weeks after AVM creation, 32 rats were treated with a single dose of GKS (20 Gy); 32 animals received sham radiation. Eight irradiated and 8 control animals were studied at each specified time point (1, 3, 6, and 12 weeks) for hemodynamic, morphological, and histological characterization.

RESULTS

Two AVMs showed partial angiographic obliteration at 6 weeks. Angiography revealed complete obliteration in 3 irradiated rats at 12 weeks. Blood flow in the ipsilateral proximal carotid artery (p < 0.001) and arterialized jugular vein (p < 0.05) was significantly lower in the irradiated group than in the control group. The arterialized vein's external diameter was significantly smaller in GKS-treated animals at 6 (p < 0.05) and 12 (p < 0.001) weeks. Histological changes included subendothelial cellular proliferation and luminal narrowing in GKS-treated animals. Neither luminal obliteration nor thrombus formation was identified at any of the time points in either irradiated or nonirradiated animals.

CONCLUSIONS

GKS produced morphological, angiographic, and histological changes in the model of AVM as early as 6 weeks after treatment. These results support the use of this model for studying methods to enhance radiation response in AVMs.

Bevacizumab for symptomatic radiation-induced tumor enlargement in pediatric low grade gliomas

BACKGROUND

Radiation therapy (RT)-induced effects in children treated for low grade glioma (LGG) can result in worsening of neurologic symptoms and clinical and radiographic deterioration. Treatment for radiation-induced tumor enlargement is based on symptom control and usually involves steroids.

PROCEDURE

We conducted a retrospective review of children with LGG treated with RT who developed symptomatic radiation-induced tumor enlargement and were managed with bevacizumab. Charts were abstracted for onset and duration of RT changes, toxicity and doses of dexamethasone and bevacizumab. Tumor volumes prior to RT, at maximal size following RT, after bevacizumab administration, and at follow-up were evaluated.

RESULTS

Five children were treated with bevacizumab for symptomatic radiation-induced tumor enlargement following RT for LGG at a median of 4.2 months (range, 1-11 months) after completion of RT. The median increase in volume of tumor was 195.4% (range, 115.5-309%) compared to the pre-RT volume. Bevacizumab 5-10 mg/kg was administered IV q 2-4 weeks as primary treatment (n = 1) or to assist in weaning patients off steroids (n = 4). All children on high dose steroids (n = 4) were weaned off or to physiologic doses of hydrocortisone. Two children developed avascular necrosis after prolonged steroid use and while on bevacizumab. Radiographically, all children showed significant improvement and are now a median of 31 months (range, 18-50 months) from the completion of radiation without requiring additional tumor-related therapy.

CONCLUSIONS

Bevacizumab can play an important role in children with symptomatic radiation changes following LGG treatment, allowing patients to avoid or minimize the toxicity of long-term steroid use. Pediatr Blood Cancer 2015;62:240-245. © 2014 Wiley Periodicals, Inc.

Radiosurgery inhibition of the Notch signaling pathway in a rat model of arteriovenous malformations

Object

Notch signaling has been suggested to promote the development and maintenance of arteriovenous malformations (AVMs), but whether radiosurgery inhibits Notch signaling pathways in AVMs is unknown. The aim of this study was to examine molecular changes of Notch signaling pathways following radiosurgery and to explore mechanisms of radiosurgical obliteration of “nidus” vessels in a rat model of AVMs.

Methods

One hundred eleven rats received common carotid artery–to–external jugular vein anastomosis to form an arteriovenous fistula (AVF) model. Six weeks postoperatively, dilated small vessels and capillaries formed a nidus. The rats with AVFs received 25-Gy radiosurgery. The expression of Notch1 and Notch4 receptors and their ligands, Delta-like1 and Delta-like4, Jagged1, Notch downstream gene target HES1, and an apoptotic marker caspase-3 in nidus vessels in the AVF rats was examined immunohistochemically and was quantified using LAS-AF software at 7 time points over a period of 42 days postradiosurgery. The interaction events between Notch1 receptor and Jagged1, as well as Notch4 receptor and Jagged1, were quantified in nidus vessels in the AVF rats using proximity ligation assay at different time points over 42 days postradiosurgery.

Results

The expression of Notch1 and Notch4 receptors, Delta-like1, Delta-like4, Jagged1, and HES1 was observed in nidus vessels in the AVF rats pre- and postradiosurgery. Radiosurgery enhanced apoptotic activity (p < 0.05) and inhibited the expression of Notch1 and Notch4 receptors and Jagged1 in the endothelial cells of nidus vessels in the AVF rats at 1, 2, 3, 7, 21, 28, and 42 days postradiosurgery (p < 0.05). Radiosurgery suppressed the interaction events between Notch1 receptor and Jagged1 (p < 0.001) as well as Notch4 receptor and Jagged1 (p < 0.001) in the endothelial cells of nidus vessels in the AVF rats over a period of 42 days postradiosurgery. Radiosurgery induced thrombotic occlusion of nidus vessels in the AVF rats. There was a positive correlation between the percentage of fully obliterated nidus vessels and time after radiosurgery (r = 0.9324, p < 0.001).

Conclusions

Radiosurgery inhibits endothelial Notch1 and Notch4 signaling pathways in nidus vessels while inducing thrombotic occlusion of nidus vessels in a rat model of AVMs. The underlying mechanisms of radiosurgery-induced AVM shrinkage could be a combination of suppressing Notch receptor signaling in blood vessel endothelial cells, leading to a reduction in nidus vessel size and thrombotic occlusion of nidus vessels.

Pituitary disease mortality: is it fiction?

During the last 20 years a tremendous improvement in the care of patients with pituitary tumors and of hypopituitarism has been achieved. If we resolve most of the possible causes of the increased cardiovascular disease and stroke mortality a normal survival is expected in these patients. Recently, a large population based study showed a decline in the risk of non-fatal stroke and of non-fatal cardiac events in GH deficient patients. This improvement was achieved by complete hormone replacement, including long term GH replacement, together with prescription of cardio protective drugs. If we follow the latest achievements in pituitary imaging, surgery techniques, hormone substitutions, cardio protective medications, we would expect a normal longevity in these patients. This review will focus on; (1) pituitary insufficiencies and hormone substitutions, (2) modes of cranial radiotherapy, and (3) new techniques in the surgery of a pituitary adenoma.

Late-onset post-irradiation vasculopathy of the posterior cerebral vasculature

Radiotherapy is extensively used in the treatment of malignant tumors of the central nervous system, but may also cause considerable morbidity and mortality, probably through damage to the remarkably vulnerable vascular system. We present two cases of infarction in the posterior cerebral vasculature related to earlier irradiation for a pineal gland tumor. Two patients were irradiated for a pineal gland tumor in young adulthood. Respectively 20 and 35 years later, they presented with a progressive neurological decline, related to early progressive atherosclerosis in the posterior cerebral vasculature. In conclusion, irradiation of the posterior cerebral territory may produce precocious atherosclerosis of posterior circulation vasculature, even decades later. When a progressive clinical decline with accumulating ischemic events is observed, together with signs of atherosclerosis, radiotherapy-related vasculopathy may be considered.

Spurious progression in pediatric brain tumors

In this study, we sought to characterize post-therapy MRI changes mimicking progression, which we refer to as "spurious progression" (SP) in children with brain tumors. We analyzed whether SP is associated with particular tumor types or therapeutic modalities. Between 2000 and 2009, we identified 181 consecutive children <21 years of age at our center who were treated for brain tumors and had at least three MRI scans within a year after completing therapy. SP was defined as MRI abnormalities characterized by increase in size, enhancement, edema, or cystic changes within 12 months following therapy, and stabilization or improvement on subsequent imaging. One-hundred forty-one patients with brain tumors were evaluable. Fifty-six (40%) had imaging abnormalities initially suggestive of disease progression; of these, 34 (24%) had true disease progression (TP). The remaining 22 (16%) had SP based on either stability, decrease in enhancement, edema, size, or disappearance of these cystic or non-cystic abnormalities. SP occurred in patients with low grade (n = 20) and high grade lesions (n = 2). Median time to SP was 2.4 months (range, 0.7-8.3 months), with time to stability, decrease, or disappearance at a median of 4 months (range 1.4-7.7 months). Five patients were clinically symptomatic from SP and were treated with steroids, cyst drainage, and/or surgery. Therefore, SP occurs more commonly in children with low grade tumors, but can also occur with high grade brain tumors, regardless of therapeutic approach.

Body mass index and annual increase of body mass index in long-term childhood cancer survivors; relationship to treatment

Purpose

Evaluation of body mass index (BMI) at final height (FH) and annual BMI increase in adult childhood cancer survivors (CCS) after treatment with anthracyclines, platinum, and/or radiotherapy.

Methods

BMI (weight/height²) was calculated retrospectively from diagnosis until FH. The prevalence of underweight (BMI < 18.5 kg/m²) and overweight (BMI ≥ 25 kg/m²)/obesity (BMI ≥ 30 kg/m²) at FH was compared with age-matched controls. The association between underweight/overweight at FH and treatment was assessed by multivariate logistic regression. Annual BMI increase after treatment was assessed by multilevel analysis. Analyses were adjusted for age and underweight/overweight at diagnosis, and age at FH.

Results

At FH the prevalence of overweight had not increased, while CCS experienced more underweight as compared to controls (14% vs. 4%, P < 0.001). Overweight at FH was associated with cranial/craniospinal radiotherapy (CRT; OR, 2.23; 95% CI, 1.17–4.26) and underweight at FH with anthracyclines > 300 mg/m² (OR, 2.84; 95% CI, 1.33–6.06). Annual BMI increase was +0.47 (0.34–0.60) kg/m²/year. In CCS, the annual BMI increase was greater in those with CRT ≥ 30 Gy as compared with those with less or no CRT (+0.15 kg/m²/year [0.04–0.25 kg/m²/year], P = 0.008) and smaller in those with a higher cumulative anthracycline dose (−0.03 kg/m²/year [−0.05 to −0.0005 kg/m²/year] per 100 mg/m², P = 0.046).

Conclusions

After treatment with anthracyclines, platinum, and/or radiotherapy, CRT-treated survivors have more overweight at FH, and a greater annual BMI increase, while anthracycline-treated survivors have more underweight at FH and a lower annual BMI increase.

Traumatic brain injury: a disease process, not an event

Traumatic brain injury (TBI) is seen by the insurance industry and many health care providers as an "event." Once treated and provided with a brief period of rehabilitation, the perception exists that patients with a TBI require little further treatment and face no lasting effects on the central nervous system or other organ systems. In fact, TBI is a chronic disease process, one that fits the World Health Organization definition as having one or more of the following characteristics: it is permanent, caused by non-reversible pathological alterations, requires special training of the patient for rehabilitation, and/or may require a long period of observation, supervision, or care. TBI increases long-term mortality and reduces life expectancy. It is associated with increased incidences of seizures, sleep disorders, neurodegenerative diseases, neuroendocrine dysregulation, and psychiatric diseases, as well as non-neurological disorders such as sexual dysfunction, bladder and bowel incontinence, and systemic metabolic dysregulation that may arise and/or persist for months to years post-injury. The purpose of this article is to encourage the classification of TBI as the beginning of an ongoing, perhaps lifelong process, that impacts multiple organ systems and may be disease causative and accelerative. Our intent is not to discourage patients with TBI or their families and caregivers, but rather to emphasize that TBI should be managed as a chronic disease and defined as such by health care and insurance providers. Furthermore, if the chronic nature of TBI is recognized by government and private funding agencies, research can be directed at discovering therapies that may interrupt the disease processes months or even years after the initiating event.

Pathological findings of fusiform dilation of the internal carotid artery following radical dissection of a craniopharyngioma

Fusiform dilation of the internal carotid artery (FDICA) after radical resection of a suprasellar craniopharyngioma has been reported. To the authors' knowledge, however, fatal conditions associated with FDICA have not been reported and pathological findings have not been obtained. The authors performed biopsy sampling of the wall of an FDICA for histopathological evaluation and found hyperplastic adventitia. This pathological result strongly supports conclusions from previous reports that FDICA has a low risk of rupture.

Factors impacting volumetric white matter changes following whole brain radiation therapy

Whole brain radiation therapy (WBRT) is one of the most effective modalities for treatment of brain metastases. With increasing cancer control there is growing concern regarding the long-term effects of treatment. These effects are seen as white matter change (WMC) on brain MRI. Severity of WMC is implicated in cognitive and functional decline in many patient groups. Our objective was to identify clinical factors associated with greater accumulation of WMC following WBRT. Through retrospective review of serial MRIs obtained from 30 patients surviving greater than 1 year after WBRT, treated at a single institution between 2002 and 2007, we calculated volumetric WMC over time using segmentation software. Changes related to tumor, secondary effects, surgery or radiosurgery were excluded. Factors that influenced the rate of WMC accumulation were identified through multivariate analysis. Following WBRT, patients accumulated WMC at an average rate of 0.07% of total brain volume per month. In multivariate analyses, greater rates of accumulation were independently associated with older age (β = 0.004, p < .0001), poor levels of glycemic control (β = 0.048, p < .0001) and hypertension diagnosis (β = 0.084, p < .0001). Long-term survivors of cancer allow assessment of late effects of treatment modalities. Radiation injury appears to be related to a steady rate of white matter damage over time, as indicated by progressive accumulation of WMC. Our results suggest that rate of WMC accumulation is enhanced by parameters such as hyperglycemia and hypertension. This has significant clinical impact by clearly identifying hyperglycemia, steroid-induced hyperglycemia, and other vascular risk factors as targets for intervention to decrease WMC in patients receiving WBRT.

Fusiform dilation of the carotid artery following radical resection of pediatric craniopharyngiomas: natural history and management

OBJECT

Fusiform dilation of the supraclinoid internal carotid artery (FDCA) is a reported occurrence following surgery for suprasellar tumors, in particular craniopharyngiomas. We report our experience of the incidence and natural history of FDCA following aggressive surgical resection of craniopharyngiomas in children.

METHODS

Between 1986 and 2006, 86 patients under the age of 21 underwent radical resection of craniopharyngiomas at our institution. Ten cases with < 1 year of follow-up imaging (6), perioperative death (3), or nonsuprasellar tumors (1) were excluded. Data were retrospectively collected on the remaining 76 patients (43 male, 33 female; mean age 9.5 years; mean tumor size 3.3 cm) to determine the risk factors for and the rate and clinical significance of FDCA.

RESULTS

Fifty patients had primary tumors and 26 patients received treatment before referral to our center. Sixty-six children (87%) had gross-total resection. At a mean follow-up time of 9.9 years, FDCA had developed in 7 patients (9.2%), all of whom had primary tumors and gross-total resection. The mean time to onset of FDCA was 6.8 months (range 3-11 months) with stabilization occurring at mean of 17.7 months (range 9-29.5 months). The mean size of the aneurysms was 9.1 mm (range 7.1-12 mm). After arrest, no lesions showed continued growth on serial imaging or produced symptoms or required treatment. There were no significant differences in age, sex, tumor size, pre- or retrochiasmatic location, extent of resection, or surgical approach (p > 0.05) between patients with and without FDCA.

CONCLUSIONS

Fusiform dilation of the supraclinoid internal carotid artery occurred in almost 10% of children following radical resection of craniopharyngiomas. In agreement with other reports, the authors concluded that FDCA probably occurs as a result of surgical manipulation of the supraclinoid carotid artery and should be managed conservatively because very few patients exhibit continued symptoms or experience growth or rupture of the lesion.

[Cerebral infarction related to intracranial radiation arteritis twenty-four years after encephalic radiation therapy]

We report a case of a resolutive late cerebral ischemic event, related to radiation induced vasculopathy of the left posterior cerebral artery, documented by MRI, situated in the irradiated volume 24 years before, for an astrocytome with malignant potential.

Responses of normal cells to ionizing radiation

Radiation-induced alterations in cellular tissue homeostasis triggered by various molecular responses at the level of inter- and intracellular signaling processes cause both acute and late effects in normal tissue after radiation therapy. Some of the underlying molecular and cellular response pathways leading to radiation-induced tissue remodeling will be discussed, with special emphasis on vascular and parenchymal tissues.

Vascular complications after radiosurgery for meningiomas

✓During the past 25 years, radiosurgery has evolved as a primary treatment modality for certain meningiomas when resection would be associated with high patient morbidity. In addition, radiosurgery is now routinely used as an adjunctive therapy for residual or recurrent meningiomas after surgical removal. In this review the authors summarize the vascular complications that occur after radiosurgery for meningiomas as well as experimental study data that give insight into the pathogenesis of this complication. These data may be useful when discussing with patients the risk/benefit ratio of choosing among conservative management, radiosurgery, and surgery.

Intracranial aneurysm following radiation therapy during childhood for a brain tumor. Case report and review of the literature

Ionizing radiation therapy is associated with pathological vascular changes in intracranial vessels, most commonly in the form of vessel thrombosis and occlusion. The development of an intracranial aneurysm following such therapy, however, is far less common. In this report the authors describe a 24-year-old man in whom a distal middle cerebral artery aneurysm developed 15 years after radiotherapy, which was given as adjuvant treatment following resection of a medulloblastoma. The patient underwent a craniotomy for microsurgical trapping of the aneurysm and was discharged without any neurological deficit. This case serves to remind clinicians of the possibility, albeit rare, that intracranial aneurysms may form following cranial radiotherapy.

Ionizing Radiation and Cardiovascular Disease

For more than 15 years the A-bomb survivor studies have shown increased noncancer mortality due to radiation exposures. The most prominent cause of this increase is circulatory disease mortality. Although the estimated relative risk is less than for solid cancers (1.2 versus 1.6 per Sv), there are measurable increases in cardiovascular disease mortality at doses greater than 0.5 Sv. The evidence for circulatory diseases in mortality studies of occupational cohorts exposed to external radiation is less compelling. It is generally accepted that atherosclerosis is an inflammatory disease of the arteries and a risk factor for myocardial infarction. Immunological markers for inflammatory disease have been shown to be dose related in A-bomb survivors. Evidence from animal studies reveals increased cardiovascular mortality and arterial endothelial damage from both neutron and, to a lesser extent, gamma exposures.

Uncommon presentation of pediatric ruptured intracranial aneurysm after radiotherapy for retinoblastoma. Case report

OBJECTIVE

Radiation-induced intracranial aneurysms are a rare entity with high mortality. Their pathogenesis is still in debate. Their unique anatomy and behavior should be considered when deciding the proper management. A background of radiation, uncommon anatomic aspects, age of presentation, and location guide us to suspect a radiation-induced etiology. We report the case of a pediatric patient with a ruptured intracranial aneurysm, who previously received radiation therapy to the orbits. We aim to contribute to the literature of this uncommon condition and stress the importance of its prompt diagnosis and treatment.

CASE DESCRIPTION

A 12-year-old boy, who received radiation therapy for recurrent bilateral retinoblastomas at age 4 months, suddenly developed severe headache associated with nausea and vomiting. A computed tomography scan revealed subarachnoid hemorrhage. A 4-vessel cerebral angiogram revealed a 2-mm aneurysm in the right A1 segment. The aneurysm was clipped successfully with excellent outcome. After 3 years of follow-up, the patient remains neurologically intact and asymptomatic. A new computed tomography angiogram revealed no new aneurysms.

CONCLUSION

Vascular abnormalities develop after radiation injury to the brain. Aneurysm formation after radiation therapy has been previously reported, probably secondary to endothelial injury. In this case, early presentation, unusual anatomy, location, and small size at rupture, in contrast with saccular aneurysms, suggest a radiation-induced etiology.

Exposure of Brain to High-Dose, Focused Gamma Rays Irradiation Produces Increase in Leukocytes-Adhesion and Pavementing in Small Intracerebral Blood Vessels

OBJECTIVE

Radiosurgery is used to destroy a predetermined target within the brain, with minimal radiation injury to the surrounding tissue. We hereby present our in vivo model to study the effects of single-session, high-dose radiation on the cerebral vessels that are targeted with radiosurgery using the Leksell Gamma Knife.

METHODS

The study was conducted in 29 adult male WT C57BL/6J mice weighing 21 to 28 g (6-8 wk old). The animals were exposed to 100 Gy single-session focused gamma ray irradiation using the Leksell Gamma Knife, and subsequently underwent intravital microscopy at different time intervals to study leukocytes and platelets adhesion patterns to the endothelium of the irradiated cerebral micro-vessels.

RESULTS

The leukocyte adhesion response showed a bell-shaped curve upon quantitative analysis with a steady increase in the number of adherent cells during the first four hours and a subsequent plateau response that was maintained during the next 24 hours. The platelet adhesion response did not demonstrate any particular pattern similar to the leukocyte response.

CONCLUSION

The experiment was able to establish in vivo increased leukocyte adhesion to the cerebral vascular endothelial cells in response to radiation injury and elaborate the time frame within which the leukocyte adhesion response increases, reaches a peak and then starts decreasing.

Cerebrovascular disease in patients with pituitary tumors

Several studies have shown that patients with acromegaly have increased mortality rates for cardiovascular disease and cerebrovascular disease (CVD). Similar associations have also been seen for patients with hypopituitarism or with non-functional pituitary adenomas. This review summarizes these data and discusses the relative importance of different risk factors for cardiovascular, especially CVD, mortality among patients with acromegaly or non-functional pituitary adenomas, and for those with hypopituitarism as a result of other causes.

Late magnetic resonance imaging features of leukoencephalopathy in children with central nervous system tumours following high-dose methotrexate and neuraxis radiation therapy

High-dose methotrexate (HDMTX) is used increasingly to treat children with central nervous system (CNS) tumours. Although the neuro-imaging features of leukoencephalopathy associated with systemic or intrathecal methotrexate administered after cranial radiation have been well described, the extent to which the sequencing of HDMTX prior to cranial radiation in infants and children predisposes to late neuroradiological features of leukoencephalopathy is unknown. This report describes the National Cancer Institute (NCI) toxicity grade of leukoencephalopathy based on magnetic resonance imaging (MRI) findings in all patients who survived 4 or more years after treatment on an earlier phase II study. These patients, with newly diagnosed CNS embryonal tumours, were in the age range 3.5-14.2 years (median 6.9 years) at diagnosis, and received four courses of pre-irradiation combination chemotherapy, including HDMTX 8 g/m(2). Following completion of the 'up-front' phase II study, all patients received conventionally fractionated whole brain doses of 36-50.4 Gy. The radiation dose and treatment volumes were determined individually according to the primary tumour location and results of extent of disease evaluations. The most recent MRI brain scans, obtained 4.0-10.5 years (median 6.5 years) after radiation therapy and comprising a minimum of T1, T1 following gadolinium and T2 sequences, were reviewed centrally to assess the neuroradiological grade of leukoencephalopathy, based on the NCI Common Terminology Criteria for Adverse Events, v3.0. Grade I changes (mild increase in subarachnoid space, and/or mild ventriculomegaly, and/or small/focal T2 hyperintensities) were evident in 8 of the 12 patients and grade II changes (moderate increase in subarachnoid space and/or moderate ventriculomegaly, and/or focal T2 hyperintensities extending to the centrum ovale) were found in the remaining 4. In conclusion, treatment with multiple courses of HDMTX prior to 36-50.4 Gy cranial radiation did not result in moderate to severe MRI features of leukoencephalopathy. Future studies in paediatric neuro-oncology patients, involving HDMTX combined with prospective neuropsychological evaluations appear justified.

Phase II trial of carmustine, cisplatin, and oral etoposide chemotherapy before radiotherapy for grade 3 astrocytoma (anaplastic astrocytoma): results of North Central Cancer Treatment Group trial 98-72-51

PURPOSE

To evaluate the efficacy of preradiotherapy (RT) chemotherapy with carmustine, cisplatin, and oral etoposide combined with RT in the treatment of newly diagnosed anaplastic astrocytoma.

METHODS AND MATERIALS

Therapy consisted of carmustine (40 mg/m(2)/d) on Days 1-3, oral etoposide (50 mg/d) on Days 1-21 and 29-49, and cisplatin (20 mg/m(2)/d i.v.) on Days 1-3 and 29-31. The regimen was repeated every 8 weeks for three cycles, with conventionally fractionated RT (5000 cGy with a 1000-cGy boost) delivered concurrently with the third cycle.

RESULTS

A total of 29 patients were enrolled between December 1999 and March 2001. For varying reasons (e.g., progression, refusal, death, or toxicity), only 48% completed the chemotherapy regimen and 76% completed RT. Grade 3-4 toxicities were observed in 14 patients (48%). The primary study endpoint was the 23-month (700-day) survival, the median survival of patients with anaplastic astrocytoma in a previous North Central Cancer Treatment Group trial. To be considered an active treatment, a maximum of 9 patient deaths (of the first 25) were allowed before 700 days. However, 14 patients had died by 700 days after therapy.

CONCLUSION

Our results have demonstrated that pre-RT chemotherapy with this regimen is insufficiently active in patients with anaplastic astrocytoma.

BOLD responses to visual stimulation in survivors of childhood cancer

Children surviving certain cancers have a high incidence of cognitive deficits caused by central nervous system (CNS) disease or treatments directed at the CNS. To establish the feasibility of using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to study cognitive deficits in survivors of childhood cancer, we tested the hypothesis that this population has the same BOLD response to visual stimulation as healthy subjects. We used BOLD fMRI to measure spatial and temporal patterns of brain activity after brief visual stimulation in 16 survivors of childhood cancer, 11 age-similar healthy siblings of survivors, and 16 healthy adults. Functional data for the survivors were analyzed with two general linear models, one used a canonical hemodynamic response function (HRF) and the other used a Fourier set as basis functions. The measured BOLD signal and brain activation patterns were similar in the survivors with both models. The BOLD signal for survivors was qualitatively similar in timing and shape, but there were significant quantitative differences as compared with healthy subjects. The activation was normally located in the primary visual cortex in 13 survivors, but the activation volume was significantly smaller in brain tumor survivors than in other groups. These findings demonstrate the feasibility of using BOLD fMRI to investigate brain function in survivors of childhood cancer. However, fMRI studies in this population must take into account effects of quantitative differences in their BOLD responses as compared to healthy subjects.

Neck irradiation, carotid injury and its consequences

Carotid stenosis is a major sequela of head and neck irradiation that has not received the attention it deserves. Its impact on the quality of life of patients can be substantial. This review discusses the incidence, pathogenesis and consequences of radiation-induced carotid stenosis following head and neck irradiation. This review is based on literature search (Medline and Pub Med) and cross-referencing. The incidence of significant carotid stenosis following head and neck irradiation range from 30% to 50%. Patients with carotid stenosis are at increased risk for stroke. Factors such as hypertension, diabetes, smoking and obesity increase the risk. Increased attention to the clinical signs of carotid stenosis and evaluation of these patients with appropriate imaging studies, together with strict implementation of management of hypertension and diabetes and, counseling on obesity and smoking have the potential to reduce the incidence of this sequela of head and neck irradiation. Those patients with severe carotid stenosis can be managed with endarterectomy or carotid artery stenting.

Intraventricular neurocytomas

The literature to date on the treatment of CNC reflects an evolution of clinical practice in neurooncology. The advent of sophisticated tools, such as MRS and molecular pathology, has facilitated more efficient diagnosis of CNC. Decreased morbidity associated with surgical intervention has resulted in better outcomes in patients undergoing resection of CNC. Prospective monitoring of treated patients with MRI coupled with judicious use of radiosurgery will likely further decrease treatment-related morbidity.

Could X-ray microbeams inhibit angioplasty-induced restenosis in the rat carotid artery?

BACKGROUND

Parallel, thin (<100 microm) planes of synchrotron-generated X rays, have been shown to spare normal tissues and preferentially damage tumors in animal models. The aim of the present study was to assess the effect of such microbeams directed unidirectionally on angioplasted rat carotid arteries.

METHODS AND MATERIALS

Three groups of Sprague-Dawley rats were studied: (a) rats with normal, untreated arteries, (b) rats treated by balloon angioplasty, but not irradiated, and (c) rats treated with balloon angioplasty and exposed to single fraction, unidirectional, parallel, microbeams an hour after angioplasty. The microbeam array, 15 mm widex7.6 mm high, consisting of 27-microm-wide beam slices, spaced 200 microm center-to-center laterally traversed the damaged artery. The in-depth in-beam dose was 150 Gy, the "valley" dose (dose midway between microbeams resulting mainly from X-ray scattering) was 4.5 Gy on average, and the "integrated" (averaged) dose was 26 Gy.

RESULTS

Microbeam irradiation, as given in the present study, was tolerated, but was insufficient to significantly suppress the neointimal hyperplasia.

DISCUSSION

The microbeam dose used is considered low. Dose escalation would be necessary to reach conclusive results regarding the X-ray microbeam efficacy to control restenosis.

Neurologic complications of radiation therapy

Injury to the central and peripheral nervous systems is an increasingly frequent consequence of standard radiation treatment protocols for tumors involving or adjacent to nervous system structures. Characteristic temporal, clinical, radiographic, and laboratory features distinguish a number of specific radiation injury syndromes, but meticulous and repeated evaluations over time are often required to establish a diagnosis. These syndromes vary with regard to prognosis and therapeutic options, and competing diagnoses with very different natural histories and therapies often mask or mimic the signs and symptoms of radiation-related nervous system injury. The ability to efficiently negotiate this complicated differential diagnostic landscape allows for early diagnosis of tumor recurrence or an alternative etiology, prompt institution of appropriate therapy, avoidance of unnecessary diagnostic studies, and confident prognostication for patients and families. Even after the diagnosis of a radiation-related complication is made, continued vigilance for additional sites or manifestations of radiation injury is mandatory. Meanwhile, further research into treatment, prevention, and the causes of individual susceptibility to radiation injury are essential.

Pseudovasculitis: mechanisms of vascular injury and clinical spectrum

Pseudovasculitis, vasculitis-like syndromes, or mimics of vasculitis represent a heterogeneous collection of disorders that are capable of simulating a vasculitic disorder. Some conditions such as cardiac myxomas, cholesterol embolization, and fibromuscular dysplasia are more apt to cause confusion, but numerous other conditions can do so also. Inappropriate diagnosis leads to delay or absence of proper management and exposure to potentially deleterious treatment modalities such as corticosteroids and cytotoxic agents. The diagnosis of a pseudovasculitic disorder requires a high index of suspicion and should always be part of the differential diagnosis of vasculitis. The endothelium is thought to be pivotal in vascular injury; much has been learned using in vitro human umbilical vein endothelial cell cultures. Application of this knowledge to human disease and to vasculitic disorders and their imitators is still premature.

Induction of a senescence-like phenotype in bovine aortic endothelial cells by ionizing radiation

Treatment of confluent monolayers of bovine aortic endothelial cells (BAEC) with gamma rays resulted in the delayed appearance of cells with an enlarged surface area that were morphologically similar to senescent cells. The majority of these cells stained positively for senescence-associated beta-galactosidase (SA-beta-gal), indicating that these cells are biochemically similar to senescent cells. The incidence of the senescence-like phenotype increased with dose (5-15 Gy) and time after irradiation. Cells with a senescence-like phenotype began to appear in the monolayer several days after irradiation. The onset of the appearance of this phenotype was accelerated by subculturing 24 h after irradiation. This acceleration was not entirely due to stimulation of progression through the cell cycle, since a high percentage of the senescent-like cells that appeared after subculture were not labeled with BrdUrd during the period after subculture. Prolonged up-regulation of expression of CDKN1A (also known as p21(CIP1/WAF1)) after irradiation was noted by Western blot analysis, again suggesting a similarity to natural senescence. Phenotypically altered endothelial cells were present in the irradiated monolayers as long as 20 weeks after irradiation, suggesting that a subpopulation of altered endothelial cells that might be functionally deficient could persist in the vasculature of irradiated tissue for a prolonged period after irradiation.

Effect of ionizing radiation on the human brain: white matter and gray matter T1 in pediatric brain tumor patients treated with conformal radiation therapy

OBJECTIVE

To test a hypothesis that fractionated radiation therapy (RT) to less than 60 Gy is associated with a dose-related change in the spin-lattice relaxation time (T1) of normal brain tissue, and that such changes are detectable by quantitative MRI (qMRI).

METHODS

Each of 21 patients received a qMRI examination before treatment, and at several time points during and after RT. A map of brain T1 was calculated and segmented into white matter and gray matter at each time point. The RT isodose contours were then superimposed upon the T1 map, and changes in brain tissue T1 were analyzed as a function of radiation dose and time following treatment. We used a mixed-model analysis to analyze the longitudinal trend in brain T1 from the start of RT to 1 year later. Predictive factors evaluated included patient age and clinical variables, such as RT dose, time since treatment, and the use of an imaging contrast agent.

RESULTS

In white matter (WM), a dose level of greater than 20 Gy was associated with a dose-dependent decrease in T1 over time, which became significant about 3 months following treatment. In gray matter (GM), there was no significant change in T1 over time, as a function of RT doses < 60 Gy. However, GM in close proximity to the tumor had an inherently lower T1 before therapy. Neither use of a contrast agent nor a combination of chemotherapy plus steroids had a significant effect on brain T1.

CONCLUSION

Results suggest that T1 mapping may be sensitive to radiation-related changes in human brain tissue T1. WM T1 appears to be unaffected by RT at doses less than approximately 20 Gy; GM T1 does not change at doses less than 60 Gy. However, tumor appears to have an effect upon adjacent GM, even before treatment. Conformal RT may offer a substantial benefit to the patient, by minimizing the volume of normal brain exposed to greater than 20 Gy.

Radiation induced vascular injury after stereotactic radiosurgery for trigeminal neuralgia: case report

BACKGROUND

Stereotactic radiosurgery is increasingly used for the treatment of medically unresponsive trigeminal neuralgia.

CASE DESCRIPTION

We present the case of a 69-year-old man with trigeminal neuralgia who underwent stereotactic radiosurgery after a failed balloon compression procedure. The radiosurgery also failed to provide the patient with any significant pain relief, and microvascular decompression of the trigeminal nerve was performed 10 months later. At operation, two adjacent veins and the superior cerebellar artery were noted to have focal changes consistent with atheromatous disease.

CONCLUSION

We postulate that the recent radiation exposure resulted in the observed vascular injury. As a result, patients having trigeminal neuralgia radiosurgery need to be followed carefully for possible delayed ischemic events secondary to radiation-induced vascular injury.