Radiation-associated cardiovascular disease

Diastolic Dysfunction Occurs Early in HER2-Positive Breast Cancer Patients Treated Concurrently With Radiation Therapy and Trastuzumab

BACKGROUND

Left ventricular ejection fraction (LVEF) is used routinely to monitor cardiac dysfunction associated with breast cancer treatment. In this study the prevalence of early left ventricular diastolic dysfunction (LVDD) and its relationship to the dose-volume of the heart irradiated were evaluated in HER2-positive breast cancer patients undergoing concurrent trastuzumab and adjuvant radiotherapy (RT).

MATERIALS AND METHODS

Data from 40 breast cancer patients treated with concurrent trastuzumab and left-sided adjuvant RT between September 2011 and October 2012 were collected prospectively. For comparison, 32 patients treated with concurrent trastuzumab and right-sided adjuvant RT and 71 patients treated with left-sided RT alone were collected retrospectively. Echocardiography was obtained before RT, immediately following RT, and 3 and 6 months after RT. Doses to the heart and left ventricle (LV) were quantified.

RESULTS

Prior to RT with concurrent trastuzumab, 11 of 29 (left) and 8 of 25 (right) patients with normal baseline left ventricular diastolic function (LVDF) developed LVDD. In patients receiving left-sided RT alone, 12 of 61 patients with normal baseline LVDF developed LVDD. Dmean, D15-D40, D60-D70, and V3-V10 of the LV were significantly higher in patients who developed LVDD after concurrent trastuzumab and left-sided RT. In contrast, only two patients developed grade 1 LVEF decrease after both concurrent treatment and left-sided RT alone.

CONCLUSION

Changes in LVDF compared with LVEF are more sensitive for early detection of cardiotoxicity. The dose-volume of the heart contributes significantly to the risk of LVDD in patients with left-sided breast cancer treated concurrently with trastuzumab.

IMPLICATIONS FOR PRACTICE

Abnormalities in diastolic function are more sensitive than changes in the left ventricular ejection fraction for detecting acute cardiotoxicity and are related to the dose-volume of the heart irradiated in patients with left-sided breast cancer receiving radiotherapy concurrently with trastuzumab. This result highlights the importance of decreasing the dose-volume of heart irradiated as a protective strategy in the treatment setting of concurrent trastuzumab and radiotherapy. Diastolic dysfunction may serve as a more sensitive tool for the early detection of cardiac damage and should be incorporated as a routine parameter in the functional monitoring of cardiotoxicity.

Beyond PET/CT in Hodgkin lymphoma: a comprehensive review of the role of imaging at initial presentation, during follow-up and for assessment of treatment-related complications

Objective

The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL). PET/CT is the imaging modality of choice in the management of Hodgkin’s lymphoma (HL). However, imaging modalities other than PET/CT such as plain radiographs, ultrasound, CT, MRI and nuclear imaging can help in various stages of clinical management of HL, including the initial workup and post-treatment surveillance. Both CT and MRI help in detecting recurrences, treatment-related pulmonary, cardiovascular and abdominal complications as well as second malignancies. Familiarity with expected post-treatment changes and complications on surveillance images can help radiologists guide patient management. The purpose of this article is to provide a comprehensive review of the role of imaging modalities other than PET/CT in the management of Hodgkin lymphoma (HL).

Main Messages

• Surveillance of HL patients is usually performed with plain radiographs and CT.

• Follow-up imaging can depict normal post-treatment changes or treatment-related complications.

• Imaging is important for the timely detection of second malignancies in HL patients.

Long-term cardiac abnormalities after cranial radiotherapy in childhood cancer survivors

BACKGROUND

Cardiac morbidity is an important late effect in long-term childhood cancer survivors (CCS) treated with cardiotoxic agents or radiotherapy (RT) on the chest. However, there is limited data on the long-term cardiac sequelae in CCS who only received cranial RT. We hypothesized that cranial RT might negatively influence cardiac structure and function.

METHODS AND RESULTS

We studied 13 CCS [mean age 30.8 (18.1-39.3) years, 7 males] who received RT only on the head for a cranial tumor and 36 age- and sex-matched healthy sibling controls. Echocardiographic follow-up was performed at median 21.7 (12.6-30.8) years after diagnosis. CCS had lower indexed diastolic LV volumes [56.0 (31.4-68.3) vs. 60.5 (41.9-94.3) mL/m(2), p = 0.024]. CCS also had reduced LV systolic and diastolic function, reflected by lower systolic LV myocardial velocities (5.3 ± 0.9 vs. 7.1 ± 1.7 cm/s, p = 0.001) and longitudinal deformation (- 17.3 ± 3.1 vs. - 20.7 ± 2.0%, p < 0.001), as well as lower diastolic LV myocardial velocities (- 10.7 ± 1.7 vs. - 12.2 ± 1.5 cm/s, p = 0.006) and deformation speed (1.1 ± 0.3 vs. 1.5 ± 0.2 1/s, p = 0.005). Additionally, in CCS insulin-like growth factor levels [15.4 (9.2-34.6) vs. 24.4 (14.8-55.5) nmol/L, p = 0.007] were lower.

CONCLUSION

Cranial RT in CCS is associated with smaller cardiac volumes and reduced systolic and diastolic LV function. This off target effect of RT might be related to lower insulin-like growth factor levels.

A tocotrienol-enriched formulation protects against radiation-induced changes in cardiac mitochondria without modifying late cardiac function or structure

Radiation-induced heart disease (RIHD) is a common and sometimes severe late side effect of radiation therapy for intrathoracic and chest wall tumors. We have previously shown that local heart irradiation in a rat model caused prolonged changes in mitochondrial respiration and increased susceptibility to mitochondrial permeability transition pore (mPTP) opening. Because tocotrienols are known to protect against oxidative stress-induced mitochondrial dysfunction, in this study, we examined the effects of tocotrienols on radiation-induced alterations in mitochondria, and structural and functional manifestations of RIHD. Male Sprague-Dawley rats received image-guided localized X irradiation to the heart to a total dose of 21 Gy. Twenty-four hours before irradiation, rats received a tocotrienol-enriched formulation or vehicle by oral gavage. Mitochondrial function and mitochondrial membrane parameters were studied at 2 weeks and 28 weeks after irradiation. In addition, cardiac function and histology were examined at 28 weeks. A single oral dose of the tocotrienol-enriched formulation preserved Bax/Bcl2 ratios and prevented mPTP opening and radiation-induced alterations in succinate-driven mitochondrial respiration. Nevertheless, the late effects of local heart irradiation pertaining to myocardial function and structure were not modified. Our studies suggest that a single dose of tocotrienols protects against radiation-induced mitochondrial changes, but these effects are not sufficient against long-term alterations in cardiac function or remodeling.

Radiation-induced heart disease: pathologic abnormalities and putative mechanisms

Breast cancer is a common diagnosis in women. Breast radiation has become critical in managing patients who receive breast conserving surgery, or have certain high-risk features after mastectomy. Most patients have an excellent prognosis, therefore understanding the late effects of radiation to the chest is important. Radiation-induced heart disease (RIHD) comprises a spectrum of cardiac pathology including myocardial fibrosis and cardiomyopathy, coronary artery disease, valvular disease, pericardial disease, and arrhythmias. Tissue fibrosis is a common mediator in RIHD. Multiple pathways converge with both acute and chronic cellular, molecular, and genetic changes to result in fibrosis. In this article, we review the pathophysiology of cardiac disease related to radiation therapy to the chest. Our understanding of these mechanisms has improved substantially, but much work remains to further refine radiation delivery techniques and develop therapeutics to battle late effects of radiation.

Endoscopic Submucosal Dissection (ESD) with Additional Therapy for Superficial Esophageal Cancer with Submucosal Invasion

OBJECTIVE

The standard treatment for submucosal esophageal cancer is esophagectomy or chemoradiotherapy (CRT). However, these treatment modalities could deteriorate the general condition and quality of life of the patients who are intolerant to invasive therapy. It is therefore important and beneficial to develop less invasive treatment protocols for these patients.

METHODS

The study included 43 patients who were clinically suspected of mucosa or submucosal esophageal cancer but underwent endoscopic submucosal dissection (ESD) as a primary treatment, due to the patients' poor performance statuses and/or preferences for less invasive therapy. According to the pathological findings and patient's general condition, whether the patient underwent additional treatments or remained hospitalized without additional treatments was thereafter decided for each patient. We retrospectively analyzed the outcomes of these patients.

RESULTS

Fifteen patients underwent additional surgery, 11 patients underwent CRT/radiation therapy (RT) and 17 patients were followed without additional treatments. During the 3-year follow-up period, the relapse-free survival rates in the patients who received or did not receive additional treatments were 88% and 64%, respectively (95% confidence interval, 0.45-0.76, p=0.04). The relapse-free and overall survival rates in the patients with additional treatments were equivalent or superior to those described in previous reports of the standard treatments. Preceding ESD contributed to reduce the local relapse significantly to approximately 3.5% and additional CRT-related toxicities.

CONCLUSION

Preceding ESD is very effective for the local control of cancer, and useful for histologically confirming the high-risk factors of relapse, such as ≥submucosal layer 2 (SM2) invasion and lymphovascular involvements. ESD with additional therapy may be a promising strategy for optimizing the selection of therapy depending on the patient's general condition.

Current Views on Anthracycline Cardiotoxicity in Childhood Cancer Survivors

Owing to their high efficacy, anthracycline antibiotics are included in numerous chemotherapeutic regimens used-often in combination with radiation therapy and/or surgery-in treatment of solid tumours and blood malignancies, both in children and adults. However, the efficacy of modern cancer treatments, owing to which the population of cancer survivors has been on the rise in recent years, may be limited by the risk of serious complications involving multiple organs and systems, including the cardiovascular system. Being an important side effect of anthracyclines, cardiotoxicity may limit the efficacy of cancer therapies in the acute phase (i.e. during the treatment) and induce the long-term sequelae, observed years after treatment completion in childhood cancer survivors. It is very important to understand the cardiotoxicity-associated mechanisms and to determine its risk factors in order to develop and/or improve the effective countermeasures. Based on published data, the paper provides an outline of current views on anthracycline cardiotoxicity and discusses such aspects as molecular mechanisms of cardiotoxicity and its clinical manifestations as well as the new preventive strategies and diagnostic techniques used for the assessment of cardiovascular abnormalities. The widespread awareness of cancer treatment-related cardiotoxicity among the healthcare professionals may significantly improve the quality of life of the childhood cancer survivors.

A novel technique for image-guided local heart irradiation in the rat

In radiotherapy treatment of thoracic, breast and chest wall tumors, the heart may be included (partially or fully) in the radiation field. As a result, patients may develop radiation-induced heart disease (RIHD) several years after exposure to radiation. There are few methods available to prevent or reverse RIHD and the biological mechanisms remain poorly understood. In order to further study the effects of radiation on the heart, we developed a model of local heart irradiation in rats using an image-guided small animal conformal radiation therapy device (SACRTD) developed at our institution. First, Monte Carlo based simulations were used to design an appropriate collimator. EBT-2 films were used to measure relative dosimetry, and the absolute dose rate at the isocenter was measured using the AAPM protocol TG-61. The hearts of adult male Sprague-Dawley rats were irradiated with a total dose of 21 Gy. For this purpose, rats were anesthetized with isoflurane and placed in a custom-made vertical rat holder. Each heart was irradiated with a 3-beam technique (one AP field and 2 lateral fields), with each beam delivering 7 Gy. For each field, the heart was visualized with a digital flat panel X-ray imager and placed at the isocenter of the 1.8 cm diameter beam. In biological analysis of radiation exposure, immunohistochemistry showed γH2Ax foci and nitrotyrosine throughout the irradiated hearts but not in the lungs. Long-term follow-up of animals revealed histopathological manifestations of RIHD, including myocardial degeneration and fibrosis. The results demonstrate that the rat heart irradiation technique using the SACRTD was successful and that surrounding untargeted tissues were spared, making this approach a powerful tool for in vivo radiobiological studies of RIHD. Functional and structural changes in the rat heart after local irradiation are ongoing.

Complication probability models for radiation-induced heart valvular dysfunction: do heart-lung interactions play a role?

Purpose

The purpose of this study is to compare different normal tissue complication probability (NTCP) models for predicting heart valve dysfunction (RVD) following thoracic irradiation.

Methods

All patients from our institutional Hodgkin lymphoma survivors database with analyzable datasets were included (n = 90). All patients were treated with three-dimensional conformal radiotherapy with a median total dose of 32 Gy. The cardiac toxicity profile was available for each patient. Heart and lung dose-volume histograms (DVHs) were extracted and both organs were considered for Lyman-Kutcher-Burman (LKB) and Relative Seriality (RS) NTCP model fitting using maximum likelihood estimation. Bootstrap refitting was used to test the robustness of the model fit. Model performance was estimated using the area under the receiver operating characteristic curve (AUC).

Results

Using only heart-DVHs, parameter estimates were, for the LKB model: D₅₀ = 32.8 Gy, n = 0.16 and m = 0.67; and for the RS model: D₅₀ = 32.4 Gy, s = 0.99 and γ = 0.42. AUC values were 0.67 for LKB and 0.66 for RS, respectively. Similar performance was obtained for models using only lung-DVHs (LKB: D₅₀ = 33.2 Gy, n = 0.01, m = 0.19, AUC = 0.68; RS: D₅₀ = 24.4 Gy, s = 0.99, γ = 2.12, AUC = 0.66). Bootstrap result showed that the parameter fits for lung-LKB were extremely robust. A combined heart-lung LKB model was also tested and showed a minor improvement (AUC = 0.70). However, the best performance was obtained using the previously determined multivariate regression model including maximum heart dose with increasing risk for larger heart and smaller lung volumes (AUC = 0.82).

Conclusions

The risk of radiation induced valvular disease cannot be modeled using NTCP models only based on heart dose-volume distribution. A predictive model with an improved performance can be obtained but requires the inclusion of heart and lung volume terms, indicating that heart-lung interactions are apparently important for this endpoint.

Valvular abnormalities detected by echocardiography in 5-year survivors of childhood cancer: a long-term follow-up study

PURPOSE

To determine the prevalence of valvular abnormalities after radiation therapy involving the heart region and/or treatment with anthracyclines and to identify associated risk factors in a large cohort of 5-year childhood cancer survivors (CCS).

METHODS AND MATERIALS

The study cohort consisted of all 626 eligible 5-year CCS diagnosed with childhood cancer in the Emma Children's Hospital/Academic Medical Center between 1966 and 1996 and treated with radiation therapy involving the heart region and/or anthracyclines. We determined the presence of valvular abnormalities according to echocardiograms. Physical radiation dose was converted into the equivalent dose in 2-Gy fractions (EQD2). Using multivariable logistic regression analyses, we examined the associations between cancer treatment and valvular abnormalities.

RESULTS

We identified 225 mainly mild echocardiographic valvular abnormalities in 169 of 545 CCS (31%) with a cardiac assessment (median follow-up time, 14.9 years [range, 5.1-36.8 years]; median attained age 22.0 years [range, 7.0-49.7 years]). Twenty-four CCS (4.4%) had 31 moderate or higher-graded abnormalities. Most common abnormalities were tricuspid valve disorders (n=119; 21.8%) and mitral valve disorders (n=73; 13.4%). The risk of valvular abnormalities was associated with increasing radiation dose (using EQD2) involving the heart region (odds ratio 1.33 per 10 Gy) and the presence of congenital heart disease (odds ratio 3.43). We found no statistically significant evidence that anthracyclines increase the risk.

CONCLUSIONS

Almost one-third of CCS treated with potentially cardiotoxic therapy had 1 or more asymptomatic, mostly mild valvular abnormalities after a median follow-up of nearly 15 years. The most important risk factors are higher EQD2 to the heart region and congenital heart disease. Studies with longer follow-up are necessary to investigate the clinical course of asymptomatic valvular abnormalities in CCS.

Premature aging induced by radiation exhibits pro-atherosclerotic effects mediated by epigenetic activation of CD44 expression

Age is undoubtedly a major risk factor for heart disease. However, the reason for this is not entirely clear. In the course of our investigation into the mechanism of radiation-induced cardiovascular disease, we made several unexpected findings that inform us on this question. We observed that human coronary endothelial cells, while being able to initiate repair of radiation-induced DNA damage, often fail to complete the repair and become senescent. Such radiation-induced cellular aging occurs through a mutation-independent route. Endothelial cells that aged naturally through replication or as a result of radiation exhibited indistinguishable characteristics. The promoter regions of the CD44 gene in aging endothelial cells become demethylated, and the proteins are highly expressed on the cell surface, making the cells adhesive for monocytes. Adhesion is a cardinal feature that recruits monocytes to the endothelium, allowing them to infiltrate the vessel wall and initiate atherosclerosis. The epigenetic activation of CD44 expression is particularly significant as it causes persistent elevated CD44 protein expression, making senescent endothelial cells chronically adhesive. In addition to understanding why cardiovascular disease increases with age, these observations provide insights into the puzzling association between radiation and cardiovascular disease and highlight the need to consider premature aging as an additional risk of radiation to human health.

MRI findings of radiation-induced myocardial damage in patients with oesophageal cancer

AIM

To evaluate radiation-induced myocardial damage after mediastinal radiotherapy using MRI.

MATERIALS AND METHODS

Between May 2010 and April 2011, delayed contrast-enhanced MRI was performed for patients who had maintained a complete response to curative radiotherapy for oesophageal cancer for more than 6 months. The patients received radiotherapy with a median total dose of 66 Gy (60-70 Gy) for the primary tumour and metastatic lymph nodes. Images of MRI were analysed by a 17-segment method recommended by the American Heart Association. A segment included mainly in the 40 Gy dose line was defined as Segment 40 Gy, a segment included mainly in the 60 Gy dose line as Segment 60 Gy, and a segment out of the radiation fields as Segment OUT. The percentage of late gadolinium enhancement (LGE) was examined in those categories. The layer in which LGE was predominantly distributed was evaluated for each patient.

RESULTS

Four hundred and eight segments in 24 patients were analysed. The median interval from completion of radiotherapy to MRI was 23.5 months (range 6-88 months). LGE was detected in 12 of the 24 patients. LGE was detected in 15.38% of Segment 40 Gy cases, 21.21% of Segment 60 Gy cases, and 0% of Segment OUT cases. LGE in mid-myocardial and subendocardial layers was detected in 11 patients and one patient, respectively.

CONCLUSION

LGE suggesting radiation induced myocardial fibrosis was observed by performing delayed contrast-enhanced MRI. Care should be taken when planning radiotherapy to avoid late cardiac damage.

Late inflammatory and thrombotic changes in irradiated hearts of C57BL/6 wild-type and atherosclerosis-prone ApoE-deficient mice

BACKGROUND AND PURPOSE

Radiation-induced heart disease represents a late complication of thoracic radiotherapy. We investigated the inflammatory and thrombotic response after local heart irradiation in wild-type and atherosclerosis-prone mice.

MATERIAL AND METHODS

Atherosclerosis-prone ApoE(-/-) and C57BL/6 wild-type mice were sacrificed 20, 40, and 60 weeks after irradiation with 0.2, 2, 8, or 16 Gy. The expression of CD31, vascular cell adhesion molecule-1 (VCAM-1), thrombomodulin (TM), and CD45 were quantified by immunofluorescence staining of heart tissue sections.

RESULTS

Microvascular density decreased at 40 weeks after 16 Gy in C57BL/6 but not in ApoE(-/-) mice. CD31 expression declined in C57BL/6 mice at 40 weeks (8 Gy), but increased in ApoE(-/-) mice at 20 (2/8/16 Gy) and 60 weeks (16 Gy). Capillary area decreased in C57BL/6 at 40 weeks (8/16 Gy) but increased in ApoE(-/-) mice at 20 weeks (16 Gy). Endocardial VCAM-1 expression remained unchanged. TM-positive capillaries decreased at 40 weeks (8/16 Gy) in C57BL/6 and at 60 weeks (2/16 Gy) in ApoE(-/-) mice. Leukocyte infiltration transiently rose 40 weeks after 8 Gy (only ApoE(-/-)) and 16 Gy. After receiving a low irradiation dose of 0.2 Gy, no significant changes were observed in any of the mouse models.

CONCLUSION

This study demonstrated that local heart irradiation affects microvascular structure and induces inflammatory/thrombotic responses in mice in a dose- and time-dependent manner. Thereby, significant prothrombotic changes were found in both strains, although they were progressive in ApoE(-/-) mice only. Proinflammatory responses, like the increase of adhesion molecules and leukocyte infiltration, were more pronounced and occurred at lower doses in ApoE(-/-) vs. C57BL/6 mice. These findings indicate that metabolic risk factors, such as decreased ApoE lipoproteins, may lead to an enhanced proinflammatory and prothrombotic late response in locally irradiated hearts.

Histopathological evaluation of melatonin as a protective agent in heart injury induced by radiation in a rat model

INTRODUCTION

Melatonin is a hormone which is known to be a powerful cardioprotective agent due to its free radical-scavenging properties. This study was carried out to evaluate whether melatonin administration prior to irradiation would have a protective effect on cardiac histopathological changes in an experimental rat model.

METHODS

Rats were divided into four groups. Single dose of 18 Gy radiation and sham radiation exposure were used in related groups. 50mg/kg dose of melatonin were injected intraperitonally 15 min prior to radiation exposure. Analyses and assessments were performed 6 months after radiation exposure.

RESULTS

Severe myocardial fibrosis was observed prominently in three regions: the apex, tips of papillary muscles and adjacent to the atrioventricular valves. Inflammation was found to be more in irradiated groups. Increased inflammation and fibrosis were in concordance. The number of mast cells was found to be decreased in irradiated groups. Myocyte necrosis and fibrosis were diminished with melatonin while vasculitis was prevented.

CONCLUSIONS

Elementary pathological lesions of radiation-induced heart disease (RIHD) are fibrosis, vascular damage, vasculitis and myocyte necrosis. Development of vasculitis was prevented by the use of melatonin. Fibrosis and necrosis were prominently decreased. Prevention of RIHD with the use of melatonin at the long term is encouraging according to the histopathological results.

Lifestyle and metabolic syndrome in adult survivors of childhood cancer: a report from the St. Jude Lifetime Cohort Study

BACKGROUND

Childhood cancer survivors (CCS) are at an increased risk of developing metabolic syndrome (MetSyn), which may be reduced with lifestyle modifications. The purpose of this investigation was to characterize lifestyle habits and associations with MetSyn among CCS.

METHODS

CCS who were ≥ 10 years from diagnosis, aged > 18 years, and participating in the St. Jude Lifetime Cohort Study completed medical and laboratory tests and a food frequency questionnaire. The Third Report of the National Cholesterol Education Program Adult Treatment Panel criteria were used to classify participants with MetSyn. Anthropometric, food frequency questionnaire, and self-reported physical activity data were used to characterize lifestyle habits according to World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) recommendations. Those who met ≥ 4 of 7 recommendations were classified as having followed guidelines. Sex-stratified log-binomial regression models were used to evaluate associations between dietary/lifestyle habits and MetSyn, adjusted for age, age at cancer diagnosis, receipt of cranial radiotherapy, education, and household income.

RESULTS

Among 1598 CCS (49.2% of whom were male, with a median age of 32.7 years [range, 18.9 years-60.0 years]), 31.8% met criteria for MetSyn and 27.0% followed WCRF/AICR guidelines. Females who did not follow WCRF/AICR guidelines were 2.4 times (95% confidence interval, 1.7-3.3) and males were 2.2 times (95% confidence interval, 1.6-3.0) more likely to have MetSyn than those who followed WCRF/AICR guidelines.

CONCLUSIONS

Adherence to a heart-healthy lifestyle is associated with a lower risk of MetSyn among CCS. There is a need to determine whether lifestyle interventions prevent or remediate MetSyn in CCS.

Macrophage phenotypes and their modulation in atherosclerosis

Atherosclerosis is the result of a chronic inflammatory response in the arterial wall related to uptake of low-density lipoprotein by macrophages and their subsequent transformation in foam cells. Monocyte-derived macrophages are the principal mediators of tissue homeostasis and repair, response to pathogens and inflammation. However, macrophages are a homogeneous cell population presenting a continuum phenotypic spectrum with, at the extremes, the classically Th-1 polarized M1 and alternatively Th-2 polarized M2 macrophage phenotypes, which have been well described. Moreover, M2 macrophages also present several subtypes often termed M2a, b, c and d, each of them expressing specific markers and exhibiting specialized properties. Macrophage plasticity is mirrored also in the atherosclerotic lesions, where different stimuli can influence the phenotype giving rise to a complex system of subpopulations, such as Mox, Mhem, M(Hb) and M4 macrophages. An abundant literature has described the potential modulators of the reciprocal skewing between pro-inflammatory M1 and anti-inflammatory M2 macrophages including lesion stage and localization, miRNA, transcription factors such as PPARγ, KLF4 and NR4A family members, high-density lipoproteins and plaque lipid content, pathways such as the rapamycin-mTOR1 pathway, molecules such as thioredoxin-1, infection by helminths and irradiation. We hope to provide an overview of the macrophage phenotype complexity in cardiovascular diseases, particularly atherosclerosis.

Adjuvant chemotherapy and radiotherapy in the treatment of non-small cell lung cancer (NSCLC)

Lung cancer is one of the most common human malignancies and remains the leading cause of cancer related deaths worldwide. Many recent technological advances led to improved diagnostics and staging of lung cancer. With development of new treatment options such as targeted therapies there might be improvement in progression free survival of patients with advanced stage non-small cell lung cancer (NSCLC). Improvement in overall survival is still reserved for selected patients and selected treatments. One of the mostly investigated therapeutic options is adjuvant treatment. There are many open issues in selection of patients and administration of appropriate adjuvant treatment.

Late cardiac effect of radiation therapy on a young woman with mediastinal Hodgkin's lymphoma

We experienced an excision of the mediastinal tumor located in left anterior mediastinum found in a 21-year-old woman. The histologic diagnosis of Hodgkin's lymphoma was obtained. After operation, she was treated with mantle field radiotherapy (total 42 Gy) followed by chemotherapy. At 43-year old, she developed constrictive pericarditis and heart failure resulted in the late cardiac effects of mediastinal irradiation. Despite pericardiectomy followed by medical treatment, her cardiac symptoms gradually worsened and she died at 51-year old. At autopsy, her heart was smaller than normal person. The residual pericardium and the surface of the myocardium had fibrous degeneration with tight adhesion and thickness that were dominant at the right atrium and ventricle. Likewise, we demonstrated that pericardiectomy scarcely led to a favorable outcome in this patient. These facts might be based on the radiation-associated cardiac effects involving any components of the cardiac structure.

Metabolic changes in serum steroids induced by total-body irradiation of female C57B/6 mice

The short- and long-term effects of a single exposure to gamma radiation on steroid metabolism were investigated in mice. Gas chromatography-mass spectrometry was used to generate quantitative profiles of serum steroid levels in mice that had undergone total-body irradiation (TBI) at doses of 0Gy, 1Gy, and 4Gy. Following TBI, serum samples were collected at the pre-dose time point and 1, 3, 6, and 9 months after TBI. Serum levels of progestins, progesterone, 5β-DHP, 5α-DHP, and 20α-DHP showed a significant down-regulation following short-term exposure to 4Gy, with the exception of 20α-DHP, which was significantly decreased at each of the time points measured. The corticosteroids 5α-THDOC and 5α-DHB were significantly elevated at each of the time points measured after exposure to either 1 or 4Gy. Among the sterols, 24S-OH-cholestoerol showed a dose-related elevation after irradiation that reached significance in the high dose group at the 6- and 9-month time points.

Cardiotoxicity and oncological treatments

BACKGROUND

Cardiotoxic and other side effects limit the usefulness of treatments for cancer.

METHOD

This article is based on pertinent articles that were retrieved by a selective search in PubMed and other databases, and on the guidelines of the European Society of Cardiology, the Association of Scientific Medical Societies in Germany, and the European Society of Medical Oncology.

RESULTS

Prospective studies have shown that some treatments for cancer are cardiotoxic. The heart damage that they cause can manifest itself as arrhythmia, arterial hypertension, thromboembolism, angina pectoris, myocardial infarction, or heart failure. It has been observed that potentially lethal complications can arise as late as 40 years after treatment of the original cancer. The anthracycline drug doxorubicin, given in a dose of 500 mg/m2 of body surface area, has been found to cause cardiac complications in 4-36% of the patients treated with it. Trastuzumab and epirubicin cause dose-limiting cardiac events in 1.7-5% of patients, depending on the dosage. Paclitaxel causes bradycardia, intracardiac conduction block, or arrhythmia in 0.5% of patients. 18% of patients treated with sunitimib or sorafenib have clinical manifestations relating to the heart (angina pectoris, dyspnea). 5-fluorouracil can cause angina pectoris at the beginning of treatment and rarely causes myocardial infarction. Cardiac radiation therapy, a form of treatment practiced in earlier decades, can cause cardiac complications 20 years after the event. The opportunity to prevent cardiac complications of anthracycline drugs with dexrazoxane is decidedly limited, but initial studies have shown that treatment with beta-blockers and ACE inhibitors lessens the likelihood of cardiotoxic side effects. When cardiac complications arise, the generally applicable rules for the treatment of each type of cardiac problem should be followed. The oncological treatment protocol should be adjusted or switched to one that is less damaging to the heart.

CONCLUSION

Treating physicians need to be thoroughly acquainted with the cardiotoxic effects of anti-cancer drugs so that they can diagnose them early on and avoid jeopardizing the overall success of treatment.

Radiation-induced alterations in mitochondria of the rat heart

Radiation therapy for the treatment of thoracic cancers may be associated with radiation-induced heart disease (RIHD), especially in long-term cancer survivors. Mechanisms by which radiation causes heart disease are largely unknown. To identify potential long-term contributions of mitochondria in the development of radiation-induced heart disease, we examined the time course of effects of irradiation on cardiac mitochondria. In this study, Sprague-Dawley male rats received image-guided local X irradiation of the heart with a single dose ranging from 3-21 Gy. Two weeks after irradiation, left ventricular mitochondria were isolated to assess the dose-dependency of the mitochondrial permeability transition pore (mPTP) opening in a mitochondrial swelling assay. At time points from 6 h to 9 months after a cardiac dose of 21 Gy, the following analyses were performed: left ventricular Bax and Bcl-2 protein levels; apoptosis; mitochondrial inner membrane potential and mPTP opening; mitochondrial mass and expression of mitophagy mediators Parkin and PTEN induced putative kinase-1 (PINK-1); mitochondrial respiration and protein levels of succinate dehydrogenase A (SDHA); and the 70 kDa subunit of complex II. Local heart irradiation caused a prolonged increase in Bax/Bcl-2 ratio and induced apoptosis between 6 h and 2 weeks. The mitochondrial membrane potential was reduced until 2 weeks, and the calcium-induced mPTP opening was increased from 6 h up to 9 months. An increased mitochondrial mass together with unaltered levels of Parkin suggested that mitophagy did not occur. Lastly, we detected a significant decrease in succinate-driven state 2 respiration in isolated mitochondria from 2 weeks up to 9 months after irradiation, coinciding with reduced mitochondrial levels of succinate dehydrogenase A. Our results suggest that local heart irradiation induces long-term changes in cardiac mitochondrial membrane functions, levels of SDH and state 2 respiration. At any time after exposure to radiation, cardiac mitochondria are more prone to mPTP opening. Future studies will determine whether this makes the heart more susceptible to secondary stressors such as calcium overload or ischemia/reperfusion.

Late effects of local irradiation on the expression of inflammatory markers in the Arteria saphena of C57BL/6 wild-type and ApoE-knockout mice

Combined action of irradiation (IR), shear stress, and high blood pressure is well recognized to induce damage to vasculature, while data on pathological effects of IR in large peripheral vessels with low blood pressure are scarce. The purpose of the present study was hence to investigate time- and dose-dependent effects of local IR on inflammatory and prothrombotic processes in the Arteria (A.) saphena of C57BL/6 wild-type and apolipoprotein E (ApoE)-knockout mice. Single doses of 2, 5, 8, 10, or 16 Gy were locally delivered to the A. saphena of the left leg of the animals. The expression of CD31, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, monocyte chemoattractant protein-1 (MCP-1), and thrombomodulin (TM) was quantified by semiautomatic TissueFax fluorescence analysis in frozen arterial sections. Follow-up periods were 3, 6, 9, 12, or 18 months. Protein expression in the arterial wall displayed dose-dependent changes. Proinflammatory reactions were observed for CD31, E-selectin, ICAM, and VCAM already at doses of 2 Gy. Anti-inflammatory changes were detected for MCP-1 and TM. The effects were more pronounced in wild-type versus ApoE(-/-) mice. Changes remain mostly transient up to 16 Gy. Dose- and time-dependent changes in inflammatory and thrombotic mediators in the wall of the A. saphena were found after local IR but did not transform into histopathological consequences.

Roles of sensory nerves in the regulation of radiation-induced structural and functional changes in the heart

PURPOSE

Radiation-induced heart disease (RIHD) is a chronic severe side effect of radiation therapy of intrathoracic and chest wall tumors. The heart contains a dense network of sensory neurons that not only are involved in monitoring of cardiac events such as ischemia and reperfusion but also play a role in cardiac tissue homeostasis, preconditioning, and repair. The purpose of this study was to examine the role of sensory nerves in RIHD.

METHODS AND MATERIALS

Male Sprague-Dawley rats were administered capsaicin to permanently ablate sensory nerves, 2 weeks before local image-guided heart x-ray irradiation with a single dose of 21 Gy. During the 6 months of follow-up, heart function was assessed with high-resolution echocardiography. At 6 months after irradiation, cardiac structural and molecular changes were examined with histology, immunohistochemistry, and Western blot analysis.

RESULTS

Capsaicin pretreatment blunted the effects of radiation on myocardial fibrosis and mast cell infiltration and activity. By contrast, capsaicin pretreatment caused a small but significant reduction in cardiac output 6 months after irradiation. Capsaicin did not alter the effects of radiation on cardiac macrophage number or indicators of autophagy and apoptosis.

CONCLUSIONS

These results suggest that sensory nerves, although they play a predominantly protective role in radiation-induced cardiac function changes, may eventually enhance radiation-induced myocardial fibrosis and mast cell activity.

Membrane signaling induced by high doses of ionizing radiation in the endothelial compartment. Relevance in radiation toxicity

Tumor areas can now be very precisely delimited thanks to technical progress in imaging and ballistics. This has also led to the development of novel radiotherapy protocols, delivering higher doses of ionizing radiation directly to cancer cells. Despite this, radiation toxicity in healthy tissue remains a major issue, particularly with dose-escalation in these new protocols. Acute and late tissue damage following irradiation have both been linked to the endothelium irrigating normal tissues. The molecular mechanisms involved in the endothelial response to high doses of radiation are associated with signaling from the plasma membrane, mainly via the acid sphingomyelinase/ceramide pathway. This review describes this signaling pathway and discusses the relevance of targeting endothelial signaling to protect healthy tissues from the deleterious effects of high doses of radiation.

A review of non-cancer effects, especially circulatory and ocular diseases

There is a well-established association between high doses (>5 Gy) of ionizing radiation exposure and damage to the heart and coronary arteries, although only recently have studies with high-quality individual dosimetry been conducted that would enable quantification of this risk adjusting for concomitant chemotherapy. The association between lower dose exposures and late occurring circulatory disease has only recently begun to emerge in the Japanese atomic bomb survivors and in various occupationally exposed cohorts and is still controversial. Excess relative risks per unit dose in moderate- and low-dose epidemiological studies are somewhat variable, possibly a result of confounding and effect modification by well-known (but unobserved) risk factors. Radiation doses of 1 Gy or more are associated with increased risk of posterior subcapsular cataract. Accumulating evidence from the Japanese atomic bomb survivors, Chernobyl liquidators, US astronauts, and various other exposed groups suggests that cortical cataracts may also be associated with ionizing radiation, although there is little evidence that nuclear cataracts are radiogenic. The dose-response appears to be linear, although modest thresholds (of no more than about 0.6 Gy) cannot be ruled out. A variety of other non-malignant effects have been observed after moderate/low-dose exposure in various groups, in particular respiratory and digestive disease and central nervous system (and in particular neuro-cognitive) damage. However, because these are generally only observed in isolated groups, or because the evidence is excessively heterogeneous, these associations must be treated with caution.

Cardiovascular effects after low-dose exposure and radiotherapy: what research is needed?

The authors of this report met at the Head Quarter of the International Atomic Energy Agency (IAEA) in Vienna, Austria, on 2-4 July 2012, for intensive discussions of an abundance of original publications on new epidemiological studies on cardiovascular effects after low-dose exposure and radiotherapy and radiobiological experiments as well as several comprehensive reviews that were published since the previous meeting by experts sponsored by the IAEA in June 2006. The data necessitated a re-evaluation of the situation with special emphasis on the consequences current experimental and clinical data may have for clinical oncology/radiotherapy and radiobiological research. The authors jointly arrived at the conclusions and recommendations presented here.

Treatment-related cardiotoxicity in survivors of childhood cancer

Treatment advances and higher participation rates in clinical trials have rapidly increased the number of survivors of childhood cancer. However, chemotherapy and radiation treatments are cardiotoxic and can cause cardiomyopathy, conduction defects, myocardial infarction, hypertension, stroke, pulmonary oedema, dyspnoea and exercise intolerance later in life. These cardiotoxic effects are often progressive and irreversible, emphasizing a need for effective prevention and treatment to reduce or avoid cardiotoxicity. Medical interventions, such as angiotensin-converting enzyme inhibitors, β-blockers, and growth hormone therapy, might be used to treat cardiotoxicity in childhood cancer survivors. Preventative strategies should include the use of dexrazoxane, which provides cardioprotection without reducing the oncological efficacy of doxorubicin chemotherapy; less-toxic anthracycline derivatives and the use of antioxidant nutritional supplements might also be beneficial. Continuous-infusion doxorubicin provides no benefit over bolus infusion in children. Identifying patient-related (for example, obesity and hypertension) and drug-related (for example, cumulative dose) risk factors for cardiotoxicity could help tailor treatments to individual patients. However, all survivors of childhood cancer are at increased risk of cardiotoxicity, suggesting that survivor screening recommendations for assessment of global risk of premature cardiovascular disease should apply to all survivors. Optimal, evidence-based monitoring strategies and multiagent preventative treatments still need to be identified.

Perioperative assessment of the cancer patient

The perioperative evaluation of patients with cancer differs from that of other patients in that the former may have received prior chemotherapy or radiation therapy. These cancer treatments have a wide range of side effects and complications that may affect patients' perioperative risks. The perioperative specialist who evaluates the cancer patient prior to surgery must be familiar with the effects of these treatments and their consequences for the major organ systems. The perioperative specialist must also be familiar with the natural history of cancer and have a basic understanding of how cancer affects the body. In this article, we review the perioperative concerns that are specific to the patient with cancer.

Ionizing radiation regulates cardiac Ca handling via increased ROS and activated CaMKII

Ionizing radiation (IR) is an integral part of modern multimodal anti-cancer therapies. IR involves the formation of reactive oxygen species (ROS) in targeted tissues. This is associated with subsequent cardiac dysfunction when applied during chest radiotherapy. We hypothesized that IR (i.e., ROS)-dependently impaired cardiac myocytes’ Ca handling might contribute to IR-dependent cardiocellular dysfunction. Isolated ventricular mouse myocytes and the mediastinal area of anaesthetized mice (that included the heart) were exposed to graded doses of irradiation (sham 4 and 20 Gy) and investigated acutely (after ~1 h) as well as chronically (after ~1 week). IR induced a dose-dependent effect on myocytes’ systolic function with acutely increased, but chronically decreased Ca transient amplitudes, which was associated with an acutely unaltered but chronically decreased sarcoplasmic reticulum (SR) Ca load. Likewise, in vivo echocardiography of anaesthetized mice revealed acutely enhanced left ventricular contractility (strain analysis) that declined after 1 week. Irradiated myocytes showed persistently increased diastolic SR Ca leakage, which was acutely compensated by an increase in SR Ca reuptake. This was reversed in the chronic setting in the face of slowed relaxation kinetics. As underlying cause, acutely increased ROS levels were identified to activate Ca/calmodulin-dependent protein kinase II (CaMKII). Accordingly, CaMKII-, but not PKA-dependent phosphorylation sites of the SR Ca release channels (RyR2, at Ser-2814) and phospholamban (at Thr-17) were found to be hyperphosphorylated following IR. Conversely, ROS-scavenging as well as CaMKII-inhibition significantly attenuated CaMKII-activation, disturbed Ca handling, and subsequent cellular dysfunction upon irradiation. Targeted cardiac irradiation induces a biphasic effect on cardiac myocytes Ca handling that is associated with chronic cardiocellular dysfunction. This appears to be mediated by increased oxidative stress and persistently activated CaMKII. Our findings suggest impaired cardiac myocytes Ca handling as a so far unknown mediator of IR-dependent cardiac damage that might be of relevance for radiation-induced cardiac dysfunction.

Evaluation of radiation-induced myocardial damage using iodine-123 β-methyl-iodophenyl pentadecanoic acid scintigraphy

We evaluated radiation-induced myocardial damage using iodine-123 β-methyl-iodophenyl pentadecanoic acid (I-123 BMIPP) scintigraphy. Between May 2010 and April 2011 we performed I-123 BMIPP scintigraphy for patients who had maintained complete response to curative radiotherapy (RT) for esophageal cancer for more than six months. We compared the area of the myocardium in the RT fields with that of reduced I-123 BMIPP uptake using a 15-segment model that is based on axial computed tomography (CT) images. We classified the segments into three categories: segments receiving 40 Gy (Segment 40 Gy), segments receiving 60 Gy (Segment 60 Gy) and segments out of the radiation fields (Segment 0 Gy). A segment with reduced uptake in the RT fields was defined as positive. A total of 510 segments in 34 patients were used for analysis. The median interval from completion of RT to I-123 BMIPP scintigraphy was 22 months (range, 6-103 months). The numbers of Segment 0 Gy, Segment 40 Gy and Segment 60 Gy were 324, 133 and 53, respectively. Reduced uptake was detected in 42.9% (57/133) of Segment 40 Gy, 67.9% (36/53) of Segment 60 Gy and 13.3% (43/324) of Segment 0 Gy. The odds ratios of 40 Gy and 60 Gy compared with regions out of the RT fields were 5.2 (95% confidence interval [CI]: 3.7-7.4) and 15.4 (95% CI: 6.9-34.6), respectively. Reduced myocardial I-123 BMIPP uptake in RT fields, suggesting RT-induced myocardial damage, was frequently observed. I-123 BMIPP myocardial scintigraphy may be useful for identifying RT-induced myocardial damage.

The PI3K/Akt/mTOR pathway is implicated in the premature senescence of primary human endothelial cells exposed to chronic radiation

The etiology of radiation-induced cardiovascular disease (CVD) after chronic exposure to low doses of ionizing radiation is only marginally understood. We have previously shown that a chronic low-dose rate exposure (4.1 mGy/h) causes human umbilical vein endothelial cells (HUVECs) to prematurely senesce. We now show that a dose rate of 2.4 mGy/h is also able to trigger premature senescence in HUVECs, primarily indicated by a loss of growth potential and the appearance of the senescence-associated markers ß-galactosidase (SA-ß-gal) and p21. In contrast, a lower dose rate of 1.4 mGy/h was not sufficient to inhibit cellular growth or increase SA-ß-gal-staining despite an increased expression of p21. We used reverse phase protein arrays and triplex Isotope Coded Protein Labeling with LC-ESI-MS/MS to study the proteomic changes associated with chronic radiation-induced senescence. Both technologies identified inactivation of the PI3K/Akt/mTOR pathway accompanying premature senescence. In addition, expression of proteins involved in cytoskeletal structure and EIF2 signaling was reduced. Age-related diseases such as CVD have been previously associated with increased endothelial cell senescence. We postulate that a similar endothelial aging may contribute to the increased rate of CVD seen in populations chronically exposed to low-dose-rate radiation.

Understanding cardiovascular injury after treatment for cancer: an overview of current uses and future directions of cardiovascular magnetic resonance

While cancer-free survival has improved over the past 20 years for many individuals with prostate, renal, breast, and hematologic malignancies, the increasingly recognized prevalence of cardiovascular (CV) events in cancer survivors has been an unintended consequence of many of the therapies that have improved these survival rates. The increase in CV events threatens to offset the improvement in cancer related survival. As a result, there is an emerging need to develop methods to identify those individuals treated for cancer at increased risk of cardiovascular events. With its inherent ability to characterize myocardial tissue and identify both cardiac and vascular dysfunction, cardiovascular magnetic resonance (CMR) has the potential to identify both subclinical and early clinical CV injury before the development of an overt catastrophic event such as a myocardial infarction, stroke, or premature cardiac death. Early identification provides an opportunity for the implementation of primary prevention strategies to prevent such events, thereby improving overall cancer survivorship and quality of life. This article reviews the etiology of CV events associated with cancer therapy and the unique potential of CMR to provide early diagnosis of subclinical CV injury related to the administration of these therapies.

Pharmacological induction of transforming growth factor-beta1 in rat models enhances radiation injury in the intestine and the heart

Radiation therapy in the treatment of cancer is dose limited by radiation injury in normal tissues such as the intestine and the heart. To identify the mechanistic involvement of transforming growth factor-beta 1 (TGF-β1) in intestinal and cardiac radiation injury, we studied the influence of pharmacological induction of TGF-β1 with xaliproden (SR 57746A) in rat models of radiation enteropathy and radiation-induced heart disease (RIHD). Because it was uncertain to what extent TGF-β induction may enhance radiation injury in heart and intestine, animals were exposed to irradiation schedules that cause mild to moderate (acute) radiation injury. In the radiation enteropathy model, male Sprague-Dawley rats received local irradiation of a 4-cm loop of rat ileum with 7 once-daily fractions of 5.6 Gy, and intestinal injury was assessed at 2 weeks and 12 weeks after irradiation. In the RIHD model, male Sprague-Dawley rats received local heart irradiation with a single dose of 18 Gy and were followed for 6 months after irradiation. Rats were treated orally with xaliproden starting 3 days before irradiation until the end of the experiments. Treatment with xaliproden increased circulating TGF-β1 levels by 300% and significantly induced expression of TGF-β1 and TGF-β1 target genes in the irradiated intestine and heart. Various radiation-induced structural changes in the intestine at 2 and 12 weeks were significantly enhanced with TGF-β1 induction. Similarly, in the RIHD model induction of TGF-β1 augmented radiation-induced changes in cardiac function and myocardial fibrosis. These results lend further support for the direct involvement of TGF-β1 in biological mechanisms of radiation-induced adverse remodeling in the intestine and the heart.

Multivariate normal tissue complication probability modeling of heart valve dysfunction in Hodgkin lymphoma survivors

PURPOSE

To establish a multivariate normal tissue complication probability (NTCP) model for radiation-induced asymptomatic heart valvular defects (RVD).

METHODS AND MATERIALS

Fifty-six patients treated with sequential chemoradiation therapy for Hodgkin lymphoma (HL) were retrospectively reviewed for RVD events. Clinical information along with whole heart, cardiac chambers, and lung dose distribution parameters was collected, and the correlations to RVD were analyzed by means of Spearman's rank correlation coefficient (Rs). For the selection of the model order and parameters for NTCP modeling, a multivariate logistic regression method using resampling techniques (bootstrapping) was applied. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC).

RESULTS

When we analyzed the whole heart, a 3-variable NTCP model including the maximum dose, whole heart volume, and lung volume was shown to be the optimal predictive model for RVD (Rs = 0.573, P<.001, AUC = 0.83). When we analyzed the cardiac chambers individually, for the left atrium and for the left ventricle, an NTCP model based on 3 variables including the percentage volume exceeding 30 Gy (V30), cardiac chamber volume, and lung volume was selected as the most predictive model (Rs = 0.539, P<.001, AUC = 0.83; and Rs = 0.557, P<.001, AUC = 0.82, respectively). The NTCP values increase as heart maximum dose or cardiac chambers V30 increase. They also increase with larger volumes of the heart or cardiac chambers and decrease when lung volume is larger.

CONCLUSIONS

We propose logistic NTCP models for RVD considering not only heart irradiation dose but also the combined effects of lung and heart volumes. Our study establishes the statistical evidence of the indirect effect of lung size on radio-induced heart toxicity.

Understanding radiation-induced cardiovascular damage and strategies for intervention

There is a clear association between therapeutic doses of thoracic irradiation and an increased risk of cardiovascular disease (CVD) in cancer survivors, although these effects may take decades to become symptomatic. Long-term survivors of Hodgkin's lymphoma and childhood cancers have two-fold to more than seven-fold increased risks for late cardiac deaths after total tumour doses of 30-40 Gy, given in 2 Gy fractions, where large volumes of heart were included in the field. Increased cardiac mortality is also seen in women irradiated for breast cancer. Breast doses are generally 40-50 Gy in 2 Gy fractions, but only a small part of the heart is included in the treatment fields and mean heart doses rarely exceeded 10-15 Gy, even with older techniques. The relative risks of cardiac mortality (1.1-1.4) are consequently lower than for Hodgkin's lymphoma survivors. Some epidemiological studies show increased risks of cardiac death after accidental or environmental total body exposures to much lower radiation doses. The mechanisms whereby these cardiac effects occur are not fully understood and different mechanisms are probably involved after high therapeutic doses to the heart, or part of the heart, than after low total body exposures. These various mechanisms probably result in different cardiac pathologies, e.g. coronary artery atherosclerosis leading to myocardial infarct, versus microvascular damage and fibrosis leading to congestive heart failure. Experimental studies can help to unravel some of these mechanisms and may identify suitable strategies for managing or inhibiting CVD. In this overview, the main epidemiological and clinical evidence for radiation-induced CVD is summarised. Experimental data shedding light on some of the underlying pathologies and possible targets for intervention are also discussed.

Effects of radiation on the epidermal growth factor receptor pathway in the heart

PURPOSE

Radiation-induced heart disease (RIHD) is a serious side-effect of thoracic radiotherapy. The epidermal growth factor receptor (EGFR) pathway is essential for the function and survival of cardiomyocytes. Hence, agents that target the EGFR pathway are cardiotoxic. Tocotrienols protect from radiation injury, but may also enhance the therapeutic effects of EGFR pathway inhibitors in cancer treatment. This study investigated the effects of local irradiation on the EGFR pathway in the heart and tests whether tocotrienols may modify radiation-induced changes in this pathway.

METHODS

Male Sprague-Dawley rats received image-guided localized heart irradiation with 21 Gy. Twenty four hours before irradiation, rats received a single dose of tocotrienol-enriched formulation or vehicle by oral gavage. At time points from 2 h to 9 months after irradiation, left ventricular expression of EGFR pathway mediators was studied.

RESULTS

Irradiation caused a decrease in the expression of epidermal growth factor (EGF) and neuregulin-1 (Nrg-1) mRNA from 6 h up to 10 weeks, followed by an upregulation of these ligands and the receptor erythroblastic leukemia viral oncogene homolog (ErbB)4 at 6 months. In addition, the upregulation of Nrg-1 was statistically significant up to 9 months after irradiation. A long-term upregulation of ErbB2 protein did not coincide with changes in transcription or post-translational interaction with the chaperone heat shock protein 90 (HSP90). Pretreatment with tocotrienols prevented radiation-induced changes at 2 weeks.

CONCLUSIONS

Local heart irradiation causes long-term changes in the EGFR pathway. Studies have to address how radiation may interact with cardiotoxic effects of EGFR inhibitors.

Cardiovascular changes in atherosclerotic ApoE-deficient mice exposed to Co60 (γ) radiation

Background

There is evidence for a role of ionizing radiation in cardiovascular diseases. The goal of this work was to identify changes in oxidative and nitrative stress pathways and the status of the endothelinergic system during progression of atherosclerosis in ApoE-deficient mice after single and repeated exposure to ionizing radiation.

Methods and Results

B6.129P2-ApoE tmlUnc mice on a low-fat diet were acutely exposed (whole body) to Co60 (γ) (single dose 0, 0.5, and 2 Gy) at a dose rate of 36.32 cGy/min, or repeatedly (cumulative dose 0 and 2 Gy) at a dose-rate of 0.1 cGy/min for 5 d/wk, over a period of 4 weeks. Biological endpoints were investigated after 3–6 months of recovery post-radiation. The nitrative stress marker 3-nitrotyrosine and the vasoregulator peptides endothelin-1 and endothelin-3 in plasma were increased (p<0.05) in a dose-dependent manner 3–6 months after acute or chronic exposure to radiation. The oxidative stress marker 8-isoprostane was not affected by radiation, while plasma 8-hydroxydeoxyguanosine and L-3,4-dihydroxyphenylalanine decreased (p<0.05) after treatment. At 2Gy radiation dose, serum cholesterol was increased (p = 0.008) relative to controls. Percent lesion area increased (p = 0.005) with age of animal, but not with radiation treatment.

Conclusions

Our observations are consistent with persistent nitrative stress and activation of the endothelinergic system in ApoE−/− mice after low-level ionizing radiation exposures. These mechanisms are known factors in the progression of atherosclerosis and other cardiovascular diseases.

Exploring the Feasibility of Establishing a Retrospective Cohort of Survivors of Adolescent and Young Adult Cancer to Study Long-Term Health Outcomes in an Integrated Managed Care Environment

PURPOSE

To determine the feasibility of conducting survivorship research for long-term health outcomes with survivors of cancer diagnosed as an adolescent or young adult (AYA) and enrolled in Kaiser Permanente Southern California (KPSC), an integrated managed care organization.

METHODS

Survivors diagnosed at ages 15-39 during 1990 and 2000 at KPSC were included. A 1:5 age-, gender-, and calendar-year-matched non-cancer KPSC comparison group was also identified. Date of cancer diagnosis was defined as the study baseline. KPSC insurance retention rate was calculated at 5 and 10 years post-baseline among survivors. Multivariable logistic regression was used to examine demographic and cancer characteristics associated with KPSC insurance retention at ≥5 years after baseline.

RESULTS

A total of 6170 AYA cancer patients were identified: 4745 (77%) and 4471 (72%) survived at 5 and 10 years after diagnosis respectively. Of these survivors, 3654 (77%) and 2817 (63%) remained insured at KPSC at 5 and 10 years post-cancer diagnosis respectively. Those aged 20-29 years when diagnosed and those with stage 4 cancer were less likely to retain KPSC insurance than other survivors. For non-cancer comparison subjects, the KPSC insurance retention rate was lower: 66% at 5 years and 51% at 10 years post-baseline. Younger age, female gender, white race, and later calendar years of study baseline were associated with a lower likelihood of KPSC insurance retention.

CONCLUSION

These results demonstrate the feasibility and potential limitations of conducting survivorship research to characterize long-term health outcomes for survivors of AYA cancer in a large, integrated managed care organization.