Non-irradiated Arteries Research Articles

Assessing the short-term effects of radiotherapy on the shear modulus of the common carotid artery as a new biomarker of radiation-induced atherosclerosis.

PurposeThe purpose of this study was to investigate the incidence of short-term atherosclerosis in the common carotid arteries following radiotherapy.MethodsThe mean radiation dose to the arteries was 49.30±15.83 Gy. A computational ultrasound method was introduced to investigate the elastic modulus. Ultrasonography was performed 2-3 cm inferior to the bifurcation region before and after radiotherapy, and sequential images were extracted from a video of each artery. Instantaneous movement of the arterial wall in the radial and longitudinal directions was extracted by implementing the maximum gradient and block matching algorithms, respectively.ResultsThere was a significant change in systolic blood pressure after radiotherapy (P=0.008). Irradiated arteries had significantly smaller systolic and end-diastolic diameters than non-irradiated arteries (P<0.001). The shear modulus was significantly different between irradiated and non-irradiated arteries (3.10±2.03 kPa vs. 1.38±0.98 kPa, P<0.001). The shear and Young moduli of radiation-induced arteries were 2.25±1.50 and 1.57±0.59 times higher than those of the pre-irradiation arteries.ConclusionThe arterial shear modulus can be considered as a new biomarker of radiation-induced atherosclerosis in the common carotid artery.

Prevention of radiotherapy-induced arterial inflammation by interleukin-1 blockade.

AimsRadiotherapy-induced cardiovascular disease is an emerging problem in a growing population of cancer survivors where traditional treatments, such as anti-platelet and lipid-lowering drugs, have limited benefits. The aim of the study was to investigate vascular inflammatory patterns in human cancer survivors, replicate the findings in an animal model, and evaluate whether interleukin-1 (IL-1) inhibition could be a potential treatment.Methods and resultsIrradiated human arterial biopsies were collected during microvascular autologous free tissue transfer for cancer reconstruction and compared with non-irradiated arteries from the same patient. A mouse model was used to study the effects of the IL-1 receptor antagonist, anakinra, on localized radiation-induced vascular inflammation. We observed significant induction of genes associated with inflammasome biology in whole transcriptome analysis of irradiated arteries, a finding supported by elevated protein levels in irradiated arteries of both, pro-caspase and caspase-1. mRNA levels of inflammasome associated chemokines CCL2, CCL5 together with the adhesion molecule VCAM1, were elevated in human irradiated arteries as was the number of infiltrating macrophages. A similar pattern was reproduced in Apoe−/− mouse 10 weeks after localized chest irradiation with 14 Gy. Treatment with anakinra in irradiated mice significantly reduced Ccl2 and Ccl5 mRNA levels and expression of I-Ab.ConclusionAnakinra, administered directly after radiation exposure for 2 weeks, ameliorated radiation induced sustained expression of inflammatory mediators in mice. Further studies are needed to evaluate IL-1 blockade as a treatment of radiotherapy-induced vascular disease in a clinical setting.

Long-term endothelial dysfunction in irradiated vessels: an immunohistochemical analysis.

Microvascular free flap reconstruction has become astandard technique in head and neck reconstructive surgery. Pre-operative radiotherapy is associated with ahigher incidence of free flap malperfusion and the need for operative revision. Irradiated vessels present characteristic histomorphological and structural changes. Alterations in endothelial cells of irradiated arteries remain incompletely investigated especially with regard to long-term changes in endothelial dysfunction supporting an intraluminal pro-thrombotic and pro-inflammatory milieu. Endothelial expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E‑ and P‑selectin, endothelial NO-synthase (eNOS), thrombomodulin and plasminogen activator inhibitor-1 (PAI-1) in irradiated and non-irradiated arteries was analysed using immunohistochemistry and Remmele scale grading. The average radiation dose was 58.7 ± 7.0 Gy; the time interval between end of radiation and tissue sampling was 106.0 ± 86.8months. Endothelial expression of ICAM-1, VCAM-1, E‑ and P‑selectin as well as PAI-1 was significantly increased in previously irradiated arteries compared with non-irradiated controls, whereas thrombomodulin and eNOS expression did not show any differences. However, when comparing non-irradiated free flap arteries with irradiated arteries from the head and neck area in respective individuals, eNOS expression was significantly lower in irradiated vessels whereas ICAM-1, VCAM-1, E‑/p-Selectin and PAI-1 showed significantly higher expression levels. There is ongoing endothelial dysfunction in terms of increased expression of pro-thrombotic and pro-inflammatory markers in irradiated arteries even years after radiotherapy. Treating this endothelial dysfunction might reduce the complication rates associated with microvascular free flap reconstructions in irradiated patients.

Abstract 652: MicroRNA-29b Mediates the Chronic Inflammatory Response in Radiotherapy-induced Vascular Disease

Radiotherapy is an established therapeutic method in many different cancer types. Its success raises a new problem, namely radiotherapy-induced vascular disease (vRTx), which typically manifests as coronary disease, heart failure or carotid stenosis. A chronic inflammatory response likely underlies vRTx, involving complex processes, such as vascular smooth muscle cell de-differentiation, oxidative stress, and ECM remodeling. These processes are tightly regulated and thus far difficult to influence therapeutically. In other diseases, a set of microRNAs (miRs) is known to orchestrate these processes. We hypothesized that they similarly could play a role in vRTx and be targets for treatment or prevention of the disease. We performed qRT-PCR screening of 11 pre-selected miRs, which identified miR-29b as significantly decreased in irradiated arteries collected from patients undergoing free tissue transfer reconstruction, compared with non-irradiated arteries from the same patient (n=15). In a vascular biology context, miR-29b is known as inhibitor of collagen- and ECM associated mRNA targets, and has been shown to play a detrimental role in aneurysm disease and advanced atherosclerotic lesions. Consistent with human tissue data, vascular smooth muscle and endothelial cells in vitro receiving two radiation doses of 2 Gy, showed decreased miR-29b upon 24 hours after exposure. In these irradiated SMCs, miR-29b induction reduced soluble collagen levels, while inhibition further increased them. Array-based tissue gene expression analysis showed that Pentraxin-3 (PTX) and dipeptidyl-peptidase 4 (DPP4), both targets of miR-29b and pivotal in inflammation and adverse wound healing, were downregulated in the same patient cohort. Carotid arteries of Apoe -/- mice treated with miR-29b mimic, 24h before and 24h after irradiation (14 Gy to the upper chest and neck), displayed a downward trend (non-significant) in Ptx3 and Dpp4 gene expression. Our results suggest that miR-29b overexpression therapy could have a place in the prevention of vRTx. To further strengthen this conclusion, additional Apoe -/- mice irradiation experiments are currently ongoing, to further establish PTX3 and DPP4 as mediators of anti-inflammatory and anti-fibrotic strategies.

O3.01 * PROGRESSION OF CAROTID INTIMA MEDIA THICKNESS AFTER RADIOTHERAPY: A PROSPECTIVE COHORT STUDY

INTRODUCTION: Carotid artery vasculopathy is a long-term complication of radiotherapy (RT) of the neck with an increased risk of cerebrovascular events. We investigated the change in carotid Intima Media Thickness (IMT) and the incidence of ischemic stroke in the first 7 years after RT. METHODS: We conducted a multicentre prospective cohort study among patients treated for Head and Neck Cancer (HNC). We assessed carotid Intima Media Thickness at baseline before and after RT with a median follow-up of 7 years. We also assessed cerebrovascular risk factors and incident vascular events. RESULTS: 48 HNC patients underwent IMT measurement at baseline and follow-up (median age 61 years, range 29-87). Mean IMT of the irradiated common carotid arteries was 0.64 mm at baseline and 0.74mm at follow-up (p = 0.002 for change). Mean delta IMT in the irradiated versus non-irradiated common carotid arteries was 0.11 and 0.02 mm (p = 0.03 for difference), respectively. In a subgroup of unilaterally irradiated patients mean change in common carotid IMT from baseline to follow-up was 0.06 mm in the irradiated artery and 0.02 mm in the non-irradiated artery (p = 0.18 for difference). Within a mean follow-up of 3 years after radiotherapy 10 patients had an ischemic event. In these patients mean common carotid IMT increase was 0.08 mm. CONCLUSION: Our study showed an increase in IMT in irradiated carotid arteries in the first 7 years after treatment of HNC, which was significantly larger than in non-irradiated arteries. Patients treated with RT for HNC have a high risk of future stroke. This knowledge needs to be used to improve diagnostic and preventive strategies.

P09.04 * CAROTID PLAQUE MRI AND STROKE AFTER RADIOTHERAPY: A LONG-TERM PROSPECTIVE COHORT STUDY

PURPOSE: Radiotherapy(RT) induced carotid artery vasculopathy and ischemic strokes are long-term complications after radiotherapy of the neck. The exact underlying pathofysiology of this RT induced atherosclerosis is not understood. The current study evaluated the presence and MRI characteristics of radiotherapy induced long-term carotid wall and cerebral complications in survivors of head and neck cancer (HNC). METHODS: Prospective multicenter long-term cohort study of 43 patients (mean age 60 years, SD 13) treated with RT of the neck because of head and neck cancer. Cerebrovascular risk factors were assessed at baseline (before RT). At follow-up (mean 7 years after RT) patients were evaluated with a MRA / MRI of the carotid arteries and the brain. First endpoint was frequency and characteristics (degree of stenosis, location, composition) of vessel wall changes. Secondary endpoints were frequency of white matter lesions, atrophy and (silent) brain infarctions. RESULTS: We found a vessel wall thickening in 55% of the irradiated common carotid arteries versus 18% in the non-irradiated. (p = 0.003). In the internal carotid arteries vessel wall thickening was found in 24% of the irradiated versus 6% of the non-irradiated arteries. (p = 0.02). Mean length of vessel wall thickening in the irradiated common and internal carotid arteries was 48.9 and 20 mm, respectively. In 50% of the irradiated common carotid arteries degree of stenosis was between 0 and 50%. MRI of the brain showed focal white matter lesions in 47% and mild atrophy in 33% of patients. CONCLUSION: Our study showed a significant increase in vessel wall changes on a long carotid segment in irradiated versus non-irradiated carotid arteries with a follow-up of 7 years after radiotherapy. An important proportion of patients also had intracranial vascular brain changes.

Increased long-term expression of pentraxin 3 in irradiated human arteries and veins compared to internal controls from free tissue transfers

BackgroundClinical studies have shown that radiotherapy increases the risk of cardiovascular disease at irradiated sites years after exposure. However, there is a lack of biological explanations in humans. We therefore examined human blood vessels exposed to radiotherapy and studied C-reactive protein (CRP) and pentraxin 3 (PTX3), a new marker for adverse cardiovascular outcome dependent on TNF- alpha (TNFα) or interleukin-1beta (IL-1β) expression.MethodsPairs of irradiated and non-irradiated human conduit arteries and veins were harvested from the same patient during autologous free tissue transfer for cancer-reconstruction at a median time of 48 weeks after radiotherapy. Differential gene expression was studied using qRT-PCR, confirmed by immunohistochemistry and cellular origins determined by immunofluorescence.ResultsGene expression in irradiated arteries compared to non-irradiated showed a consistent up-regulation of PTX3 in all patients and in a majority of veins (p < 0.001). Both TNFα and IL-1β were increased in irradiated compared to non-irradiated arteries (p < 0.01) and IL-1β correlated to the PTX3 expression (p = 0.017). Immunohistochemical and immunofluorescence staining confirmed an increased expression of PTX3 in endothelial cells, macrophages and smooth muscle cells.ConclusionsThe sustained expression of PTX3 in arteries and veins tie biological evidence in humans to clinical studies and encourage further exploration of innate immunity in the pathogenesis of a radiation-induced vasculopathy.

Accelerated progression of carotid stenosis in patients with previous external neck irradiation

ObjectiveRadiotherapy to the head and neck often results in carotid stenosis, but the course of disease is unknown. We investigated the natural history and progression of asymptomatic carotid stenosis induced by external irradiation. Patients and methodsThe study included 130 carotid arteries in 95 patients who had received external radiation therapy to the head and neck area and who had asymptomatic, mild internal carotid artery or common carotid artery stenosis. Stenosis of 15% to 49% on duplex ultrasound (US) scans defined mild (<50%) disease. Another 95 arteries in 74 patients with matched degree of carotid artery stenosis but who had not received radiation therapy were used as control. Both groups were followed up prospectively with serial duplex US scanning, and degree of carotid artery stenosis was categorized as 15% to 49%, 50% to 69%, 70% to 99%, and occlusion. Progression of carotid artery stenosis was defined as increase in stenosis from less than 50% to 50% or greater at ultrasonography. Secondary end points included progression to higher disease category, new cerebrovascular symptoms, and death. Data from irradiated arteries was compared with control data with the life table method. A Cox regression model was used to analyze disease progression, adjusted for covariates of sex, age, smoking, diabetes, and hypertension. ResultsMean follow-up was 36 months. Adjusted freedom from progression rates at 3 years were 65% for irradiated arteries and 87% for control arteries at life-table analysis (P = .035; odds ratio, 3.1). The annualized progression rate from less than 50% to 50% or greater in irradiated arteries was 15.4%, compared with 4.8% in nonirradiated arteries. A long history of cervical irradiation (>6 years) was the only significant risk factor for disease progression. There was no difference between the two groups regarding development of new symptoms or mortality. ConclusionsCarotid stenosis associated with external irradiation progresses more rapidly compared with nonirradiated atherosclerotic arteries. Aggressive surveillance is recommended.

Histomorphometric evaluation of (198)Au endovascular brachytherapy in a renal artery restenosis model in rabbits.

The main mid-term complication of percutaneous transluminal angioplasty of the renal artery is restenosis, which occurs in up to 50% of patients. Although no pharmacologic agent to date has been effective in preventing restenosis, both beta-ray emitters and gamma-ray emitters used in endovascular brachytherapy have been shown to reduce coronary restenosis. The objectives of this study were to evaluate the efficacy of (198)Au endovascular brachytherapy in preventing restenosis after percutaneous transluminal renal angioplasty and to determine the radiation dose to the operator. Twenty-one New Zealand white rabbits (10 females and 11 males) weighing an average of 3.5 kg (range, 3.2-3.8 kg) who had been fed a normal diet underwent bilateral 33% overdilatation with deendothelialization of the renal arteries. After 7 weeks, the induced renal artery stenoses were treated by percutaneous transluminal renal angioplasty. The rabbits were randomly assigned to one of three groups before receiving endovascular 25-Gy irradiation at a radial 2.0-mm depth with a 0.5 x 15 mm (198)Au wire (106 MBq). The right renal artery was irradiated in group A; the left, in group B. The rabbits in group C randomly received a right- or left-sided dummy wire. Operator exposure to radiation was measured using thermoluminescent dosimeters and ionization chambers. The rabbits were sacrificed after 3 weeks. The aorta and renal arteries were perfusion-fixed. The renal arteries were removed for histologic and histomorphometric study. Forty-two renal arteries were cut into a series of 4- micro m-thick slices. Five arteries were thrombosed (two in the irradiated group and three in the control group, p > 0.05). In the patent arteries (n = 37), the average neointimal area was 0.068 mm(2) (range, 0.009-0.234 mm(2)) in 15 irradiated segments (315 slices total), whereas the average neointimal area was 0.135 mm(2) (range, 0.016-0.324 mm(2)) in 22 control segments (462 slices total) (analysis of variance, p < 0.009), showing a percentage area of restenosis of 10.4% in irradiated arteries and 43.4% in non-irradiated arteries (p < 0.0003). Radiation dose per procedure to the operator was 0.034 mSv in the index finger, 0.024 mSv in the wrist, and undectable in the body. Endovascular brachytherapy with (198)Au appears to inhibit early renal artery restenosis and exposes the operator to a safe level of radiation.

Radiation therapy impairs endothelium-dependent vasodilation in humans

OBJECTIVESThe objective of this study was to test the hypothesis that external-beam radiation induces a chronic impairment of endothelium-dependent vasodilation.BACKGROUNDRadiation therapy is used commonly in the treatment of cancer and is associated with an increased incidence of adverse vascular events related to the field of radiation, including stroke and myocardial infarction. As endothelial injury is central to the pathogenesis of vascular diseases, we hypothesized that radiotherapy induces arterial endothelial dysfunction.METHODSSixteen women with unilateral breast cancer who underwent standard external-beam radiation therapy to the breast and axilla >3 years before enrollment and ten healthy women were studied. Vascular ultrasonography was used to image both the artery exposed to radiation and the contralateral artery. Flow-mediated, endothelium-dependent vasodilation and endothelium-independent vasodilation to nitroglycerin of both axillary arteries were measured.RESULTSEndothelium-dependent vasodilation was significantly impaired in the irradiated axillary arteries compared with the contralateral, nonirradiated arteries (−0.4 ± 0.4% vs. 3.2 ± 0.8%, p < 0.001) and also compared with control subjects’ arteries (−0.4 ± 0.4% vs. 2.5 ± 0.6%, p < 0.001). In contrast, endothelium-independent vasodilation was greater in the arteries that received radiation compared with the contralateral arteries (3.8 ± 0.5% vs. 2.0 ± 0.4%, p < 0.05) and also compared with control arteries (3.8 ± 0.5% vs. 2.5 ± 0.4%, p < 0.05).CONCLUSIONSExternal beam radiation therapy impairs endothelium-dependent vasodilation of conduit arteries, implicating a decrease in the bioavailability of nitric oxide. These abnormalities may contribute to the development of arterial occlusive disease and associated clinical events.

Late Thrombosis After Radiation

Five years after Condado et al1 first treated human coronary arteries with brachytherapy, there is ongoing clinical investigation into its safety and efficacy in preventing restenosis. As with any novel technique, unexpected complications may dampen early high expectations and result in pessimism and skepticism. However, time, experience, and complete data analysis will determine the reality. Costa and coworkers2 may be reacting prematurely by reporting a new phenomenon in interventional cardiology entitled “late, sudden thrombosis after PTCA plus radiotherapy.” They report 6 (6.6%) of 91 patients who presented with late total occlusion/thrombosis at angiographic follow-up; these patients were enrolled into different radiation protocols using different β-emitters at different prescribed doses. Late total occlusion or late thrombosis is a valid concern, especially when associated with acute myocardial infarction (MI). However, can we really draw any conclusion from 6 heterogeneous case reports taken from a small cohort of patients in the absence of a control group? Is this announcement based on too few data, and is it premature? An editorial based on a Brief Rapid Communication mandates the editorialist to gather additional information, disclose his own insights, and provide the readers (the jury in this case) with as much information as possible. Acute thrombosis occurs during or early after intervention, and subacute thrombosis occurs within the subsequent 30 days. Both usually present with unstable symptoms and angiographic evidence of thrombus. However, the definition of late thrombosis may be problematic. It may not present with symptoms. It may be detected only when follow-up angiography shows a late total occlusion, which could also be the result of progressive intimal hyperplasia. Late total occlusion/thrombosis should be defined as any angiographically documented total occlusion >30 days after the procedure. For patients who have a patent treatment site at 6 months and subsequently develop a total …