Radiation injury to the heart

Advances in Screening for Radiation-Associated Cardiotoxicity in Cancer Patients

PURPOSE OF REVIEW

Radiation is foundational to the treatment of cancer and improves overall survival. Yet, it is important to recognize the potential cardiovascular effects of radiation therapy and how to best minimize or manage them. Screening-both through imaging and with biomarkers-can potentially identify cardiovascular effects early, allowing for prompt initiation of treatment to mitigate late effects.

RECENT FINDINGS

Cardiac echocardiography, magnetic resonance imaging (MRI), computed tomography, and measurements of troponin and natriuretic peptides serve as the initial screening tests of choice for RICD. Novel imaging applications, including positron emission tomography and specific MRI parameters, and biomarker testing, including myeloperoxidase, growth differentiation factor 15, galectin 3, micro-RNA, and metabolomics, hold promise for earlier detection and more specific characterization of RICD. Advances in imaging and novel applications of biomarkers have potential to identify subclinical RICD and may reveal opportunities for early intervention. Further research is needed to elucidate optimal imaging screening modalities, biomarkers, and surveillance strategies.

Novel simulation for dosimetry impact of diaphragm respiratory motion in four-dimensional volumetric modulated arc therapy for esophageal cancer

BACKGROUND AND PURPOSE

The diaphragm respiratory motion (RM) could impact the target dose robustness in the lower esophageal cancer (EC). We aimed to develop a framework evaluating the impact of different RM patterns quantitatively in one patient, by creating virtual four-dimensional computed-tomography (v4DCT) images, which could lead to tailored treatment for the breathing pattern. We validated virtual 4D radiotherapy (v4DRT) along with exploring the acceptability of free-breathing volumetric modulated arc therapy (FB-VMAT).

METHODS AND MATERIALS

We assessed 10 patients with superficial EC through their real 4DCT (r4DCT) scans. v4DCT images were derived from the end-inhalation computed tomography (CT) image (reference CT) and the v4DRT dose was accumulated dose over all phases. r4DRT diaphragm shifts were applied with magnitudes derived from r4DCT scans; clinical target volume (CTV) dose of v4DRT was compared with that of r4DRT to validate v4DRT. CTV dosage modifications and planning organ at risk volume (PRV) margins of the spinal cord were examined with the diaphragm movement. The percentage dose differences (ΔDx) were determined between the v4DRT and the dose calculated on the reference CT image.

RESULTS

The CTV ΔDx between the r4DRT and v4DRT were within 1% in cases with RM ≦ 15 mm. The average ΔD100% and ΔDmean of the CTV ranging from 5 to 15 mm of diaphragm motion was 0.3% to 1.7% and 0.1% to 0.4%, respectively. All CTV index changes were within 3% and ΔD1cc and ΔD2cc of Cord PRV were within 1%.

CONCLUSION

We postulate a novel method for evaluating the CTV robustness, comparable to the conventional r4DCT method under the diaphragm RM ≦ 15 mm permitting an impact of within 3% in FB-VMAT for EC on the CTV dose distribution.

Innate immune signaling drives late cardiac toxicity following DNA-damaging cancer therapies

Late cardiac toxicity is a potentially lethal complication of cancer therapy, yet the pathogenic mechanism remains largely unknown, and few treatment options exist. Here we report DNA-damaging agents such as radiation and anthracycline chemotherapies inducing delayed cardiac inflammation following therapy due to activation of cGAS- and STING-dependent type I interferon signaling. Genetic ablation of cGAS-STING signaling in mice inhibits DNA damage-induced cardiac inflammation, rescues late cardiac functional decline, and prevents death from cardiac events. Treatment with a STING antagonist suppresses cardiac interferon signaling following DNA-damaging therapies and effectively mitigates cardiac toxicity. These results identify a therapeutically targetable, pathogenic mechanism for one of the most vexing treatment-related toxicities in cancer survivors.

Inter- and intrafractional 4D dose accumulation for evaluating ΔNTCP robustness in lung cancer

BACKGROUND AND PURPOSE

Model-based selection of proton therapy patients relies on a predefined reduction in normal tissue complication probability (NTCP) with respect to photon therapy. The decision is necessarily made based on the treatment plan, but NTCP can be affected when the delivered treatment deviates from the plan due to delivery inaccuracies. Especially for proton therapy of lung cancer, this can be important because of tissue density changes and, with pencil beam scanning, the interplay effect between the proton beam and breathing motion.

MATERIALS AND METHODS

In this work, we verified whether the expected benefit of proton therapy is retained despite delivery inaccuracies by reconstructing the delivered treatment using log-file based dose reconstruction and inter- and intrafractional accumulation. Additionally, the importance of two uncertain parameters for treatment reconstruction, namely deformable image registration (DIR) algorithm and α/β ratio, was assessed.

RESULTS

The expected benefit or proton therapy was confirmed in 97% of all studied cases, despite regular differences up to 2 percent point (p.p.) NTCP between the delivered and planned treatments. The choice of DIR algorithm affected NTCP up to 1.6 p.p., an order of magnitude higher than the effect of α/β ratio.

CONCLUSION

For the patient population and treatment technique employed, the predicted clinical benefit for patients selected for proton therapy was confirmed for 97.0% percent of all cases, although the NTCP based proton selection was subject to 2 p.p. variations due to delivery inaccuracies.

Serum RNA biomarkers for predicting survival in non-human primates following thoracic radiation

In a mass radiation exposure, the healthcare system may rely on differential expression of miRNA to determine exposure and effectively allocate resources. To this end, miRNome analysis was performed on non-human primate serum after whole thorax photon beam irradiation of 9.8 or 10.7 Gy with dose rate 600 cGy/min. Serum was collected up to 270 days after irradiation and sequenced to determine immediate and delayed effects on miRNA expression. Elastic net based GLM methods were used to develop models that predicted the dose vs. controls at 81% accuracy at Day 15. A three-group model at Day 9 achieved 71% accuracy in determining if an animal would die in less than 90 days, between 90 and 269 days, or survive the length of the study. At Day 21, we achieved 100% accuracy in determining whether an animal would later develop pleural effusion. These results demonstrate the potential ability of miRNAs to determine thorax partial-body irradiation dose and forecast survival or complications early following whole thorax irradiation in large animal models. Future experiments incorporating additional doses and independent animal cohorts are warranted to validate these results. Development of a serum miRNA assay will facilitate the administration of medical countermeasures to increase survival and limit normal tissue damage following a mass exposure.

Cardiotoxicity in pediatric lymphoma survivors

INTRODUCTION

Over the past five decades, the diagnosis and management of children with various malignancies have improved tremendously. As a result, an increasing number of children are long-term cancer survivors. With improved survival, however, has come an increased risk of treatment-related cardiovascular complications that can appear decades later.

AREAS COVERED

This review discusses the pathophysiology, epidemiology and effects of treatment-related cardiovascular complications from anthracyclines and radiotherapy in pediatric lymphoma survivors. There is a paucity of evidence-based recommendations for screening for and treatment of cancer therapy-induced cardiovascular complications. We discuss current preventive measures and strategies for their treatment.

EXPERT OPINION

Significant cardiac adverse effects occur due to radiation and chemotherapy received by patients treated for lymphoma. Higher lifetime cumulative doses, female sex, longer follow-up, younger age, and preexisting cardiovascular disease are associated with a higher incidence of cardiotoxicity. With deeper understanding of the mechanisms of these adverse cardiac effects and identification of driver mutations causing these effects, personalized cancer therapy to limit cardiotoxic effects while ensuring an adequate anti-neoplastic effect would be ideal. In the meantime, expanding the use of cardioprotective agents with the best evidence such as dexrazoxane should be encouraged and further studied.

Monitoring of Metabolic Syndrome and Cardiovascular Disease in Childhood Cancer Survivors

Advances in cancer treatment have significantly improved childhood cancer survival, although metabolic syndrome and cardiovascular disease are common long-term complications that may occur years after treatment. Childhood cancer survivors may not receive appropriate follow-up due to lack of communication between oncologists and primary care physicians, or, from lack of awareness of possible long-term metabolic and cardiovascular complications after cancer treatment. We, therefore, reviewed current evidence on long-term effects of cancer therapy, and appropriate monitoring for long-term treatment effects in childhood cancer survivors that could lead to early detection and prompt treatment to prevent future cardiovascular events.

Late Health Effects of Partial Body Irradiation Injury in a Minipig Model Are Associated with Changes in Systemic and Cardiac IGF-1 Signaling

Clinical, epidemiological, and experimental evidence demonstrate non-cancer, cardiovascular, and endocrine effects of ionizing radiation exposure including growth hormone deficiency, obesity, metabolic syndrome, diabetes, and hyperinsulinemia. Insulin-like growth factor-1 (IGF-1) signaling perturbations are implicated in development of cardiovascular disease and metabolic syndrome. The minipig is an emerging model for studying radiation effects given its high analogy to human anatomy and physiology. Here we use a minipig model to study late health effects of radiation by exposing male Göttingen minipigs to 1.9–2.0 Gy X-rays (lower limb tibias spared). Animals were monitored for 120 days following irradiation and blood counts, body weight, heart rate, clinical chemistry parameters, and circulating biomarkers were assessed longitudinally. Collagen deposition, histolopathology, IGF-1 signaling, and mRNA sequencing were evaluated in tissues. Our findings indicate a single exposure induced histopathological changes, attenuated circulating IGF-1, and disrupted cardiac IGF-1 signaling. Electrolytes, lipid profiles, liver and kidney markers, and heart rate and rhythm were also affected. In the heart, collagen deposition was significantly increased and transforming growth factor beta-1 (TGF-beta-1) was induced following irradiation; collagen deposition and fibrosis were also observed in the kidney of irradiated animals. Our findings show Göttingen minipigs are a suitable large animal model to study long-term effects of radiation exposure and radiation-induced inhibition of IGF-1 signaling may play a role in development of late organ injuries.

Early Changes in Rat Heart After High-Dose Irradiation: Implications for Antiarrhythmic Effects of Cardiac Radioablation

Background

Noninvasive cardiac radioablation is employed to treat ventricular arrhythmia. However, myocardial changes leading to early‐period antiarrhythmic effects induced by high‐dose irradiation are unknown. This study investigated dose‐responsive histologic, ultrastructural, and functional changes within 1 month after irradiation in rat heart.

Methods and Results

Whole hearts of wild‐type Lewis rats (N=95) were irradiated with single fraction 20, 25, 30, 40, or 50 Gy and explanted at 1 day or 1, 2, 3, or 4 weeks’ postirradiation. Microscopic pathologic changes of cardiac structures by light microscope with immunohistopathologic staining, ultrastructure by electron microscopy, and functional evaluation by ECG and echocardiography were studied. Despite high‐dose irradiation, no myocardial necrosis and apoptosis were observed. Intercalated discs were widened and disrupted, forming uneven and twisted junctions between adjacent myocytes. Diffuse vacuolization peaked at 3 weeks, suggesting irradiation dose‐responsiveness, which was correlated with interstitial and intracellular edema. CD68 immunostaining accompanying vacuolization suggested mononuclear cell infiltration. These changes were prominent in working myocardium but not cardiac conduction tissue. Intracardiac conduction represented by PR and QTc intervals on ECG was delayed compared with baseline measurements. ST segment was initially depressed and gradually elevated. Ventricular chamber dimensions and function remained intact without pericardial effusion.

Conclusions

Mononuclear cell–related intracellular and extracellular edema with diffuse vacuolization and intercalated disc widening were observed within 1 month after high‐dose irradiation. ECG indicated intracardiac conduction delay with prominent ST‐segment changes. These observations suggest that early antiarrhythmic effects after cardiac radioablation result from conduction disturbances and membrane potential alterations without necrosis.

Reducing Heart Dose with Protons and Cardiac Substructure Sparing for Mediastinal Lymphoma Treatment

Purpose

Electrocardiogram-gated computed tomography with coronary angiography can be used for cardiac substructure sparing (CSS) optimization, which identifies and improves avoidance of cardiac substructures when treating with intensity modulated radiotherapy (IMRT). We investigated whether intensity modulated proton therapy (IMPT) would further reduce dose to cardiac substructures for patients with mediastinal lymphoma.

Patients and Methods

Twenty-one patients with mediastinal lymphoma were enrolled and underwent electrocardiogram-gated computed tomography angiography during or shortly after simulation for radiotherapy planning. Thirteen patients with delineated cardiac substructures underwent comparative planning with both IMPT and IMRT. Plans were normalized for equivalent (95%) target volume coverage for treatment comparison.

Results

Thirteen patients met criteria for this study. The median size of the mediastinal lymphadenopathy was 7.9 cm at the greatest diameter. Compared with IMRT-CSS, IMPT-CSS significantly reduced mean dose to all cardiac substructures, including 3 coronary arteries and 4 cardiac valves. Use of IMPT significantly reduced average whole-heart dose from 9.6 to 4.9 Gy (P < .0001), and average mean lung dose was 9.7 vs 5.8 Gy (P < .0001). Prospectively defined clinically meaningful improvement was observed in at least 1 coronary artery in 9 patients (69%), at least 1 cardiac valve in 10 patients (77%), and whole heart in all 13 patients.

Conclusions

For patients with mediastinal lymphoma, IMPT-CSS treatment planning significantly reduced radiation dose to cardiac substructures. The significant improvements outlined in this study for proton therapy suggest possible clinical improvement in alignment with previous analyses of CSS optimization.

Automatic segmentation of cardiac structures for breast cancer radiotherapy

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We developed an automatic method to segment cardiac sub-structures for radiotherapy planning CTs.

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The Dice Similarity Coefficients and Average Surface Distance were up to 97% and < 11 mm, respectively.

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The whole heart showed the absolute dose difference < 0.3 Gy whereas the coronary arteries showed < 2.3 Gy in breast radiotherapy simulations.

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No notable improvement in our method beyond 10 atlases and using the manual guide points.

Background and purpose

We developed an automatic method to segment cardiac substructures given a radiotherapy planning CT images to support epidemiological studies or clinical trials looking at cardiac disease endpoints after radiotherapy.

Material and methods

We used a most-similar atlas selection algorithm and 3D deformation combined with 30 detailed cardiac atlases. We cross-validated our method within the atlas library by evaluating geometric comparison metrics and by comparing cardiac doses for simulated breast radiotherapy between manual and automatic contours. We analyzed the impact of the number of cardiac atlas in the library and the use of manual guide points on the performance of our method.

Results

The Dice Similarity Coefficients from the cross-validation reached up to 97% (whole heart) and 80% (chambers). The Average Surface Distance for the coronary arteries was less than 10.3 mm on average, with the best agreement (7.3 mm) in the left anterior descending artery (LAD). The dose comparison for simulated breast radiotherapy showed differences less than 0.06 Gy for the whole heart and atria, and 0.3 Gy for the ventricles. For the coronary arteries, the dose differences were 2.3 Gy (LAD) and 0.3 Gy (other arteries). The sensitivity analysis showed no notable improvement beyond ten atlases and the manual guide points does not significantly improve performance.

Conclusion

We developed an automated method to contour cardiac substructures for radiotherapy CTs. When combined with accurate dose calculation techniques, our method should be useful for cardiac dose reconstruction of a large number of patients in epidemiological studies or clinical trials.

Mapping genetic modifiers of radiation-induced cardiotoxicity to rat chromosome 3

Radiation therapy is used in ~50% of cancer patients to reduce the risk of recurrence and in some cases improve survival. Despite these benefits, doses can be limited by toxicity in multiple organs, including the heart. The underlying causes and biomarkers of radiation-induced cardiotoxicity are currently unknown, prompting the need for experimental models with inherent differences in sensitivity and resistance to the development of radiation-induced cardiotoxicity. We have identified the parental SS (Dahl salt-sensitive/Mcwi) rat strain to be a highly-sensitized model of radiation-induced cardiotoxicity. In comparison, substitution of rat chromosome 3 from the resistant BN (Brown Norway) rat strain onto the SS background (SS-3BN consomic) significantly attenuated radiation-induced cardiotoxicity. SS-3BN rats had less radiation-induced cardiotoxicity than SS rats, as measured by survival, pleural and pericardial effusions, echocardiogram parameters, and histological damage. Mast cells, previously shown to have predominantly protective roles in radiation-induced cardiotoxicity, were increased in the more resistant SS-3BN hearts postradiation. RNA sequencing from SS and SS-3BN hearts at 1 wk postradiation revealed 5,098 differentially expressed candidate genes across the transcriptome and 350 differentially expressed genes on rat chromosome 3, which coincided with enrichment of multiple pathways, including mitochondrial dysfunction, sirtuin signaling, and ubiquitination. Upstream regulators of enriched pathways included the oxidative stress modulating transcription factor, Nrf2, which is located on rat chromosome 3. Nrf2 target genes were also differentially expressed in the SS vs. SS-3BN consomic hearts postradiation. Collectively, these data confirm the existence of heritable modifiers in radiation-induced cardiotoxicity and provide multiple biomarkers, pathways, and candidate genes for future analyses. NEW & NOTEWORTHY This novel study reveals that heritable genetic factors have the potential to modify normal tissue sensitivity to radiation. Gene variant(s) on rat chromosome 3 can contribute to enhanced cardiotoxicity displayed in the SS rats vs. the BN and SS-3BN consomic rats. Identifying genes that lead to understanding the mechanisms of radiation-induced cardiotoxicity represents a novel method to personalize radiation treatment, as well as predict the development of radiation-induced cardiotoxicity.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H₂ appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H₂ has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H₂ may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Dosimetric Comparison of Three-Dimensional Conformal Radiotherapy (3D-CRT) and Intensity Modulated Radiotherapy Techniques (IMRT) with Radiotherapy Dose Simulations for Left-Sided Mastectomy Patients

Objective

To compare 3-dimensional conformal radiotherapy (3D-CRT) and intensity modulated radiotherapy (IMRT) techniques on the target tissue and critical organ doses in terms of dosimetry, during treatment planning of patient's post-mastectomy radiotherapy (PMRT) to the left chest wall.

Materials and Methods

Twenty breast cancer patients with left-sided post-mastectomy have selected for PMRT both 3D-CRT and IMRT techniques. Dosimetric calculation of dose simulation in Eclipse treatment planning system have been performed. Organs at risk with the maximum dose, minimum dose, mean dose, D95, conformity and homogeneity indexes and total monitor unit for the Planning Target Volume were compared in terms of the critical organ doses.

Results

There was no significant difference between the two treatment planning techniques in terms of maximum, minimum, mean dose and heterogeneity index (p>0.05). At low doses, the dose received at the heart was significantly lower with the 3D-CRT technique, but there was no statistically significant difference between the two techniques at the maximum and average doses in the high dose regions.

Conclusion

For PMRT to the left chest wall, IMRT significantly improves the conformity of plan and reduce the high-dose volumes of ipsilateral lung and heart compared to 3D-CRT, but 3D-CRT is superior in terms of low-dose volume.

Cardiovascular complications after radiotherapy

Over the past decades, effective cancer therapies have resulted in a significant improvement in the survival rates for a number of cancers and an increase in the number of cancer survivors. Radiation therapy is widely used in the treatment of cancer, and it can induce various cardiotoxicities that differ considerably from chemotherapy-induced cardiotoxicity. They occur primarily as late radiation-induced complications, several years from the end of anticancer treatment and present as coronary artery disease, heart failure, pericardial disease, valvular heart disease and arrhythmias. Patients who recovered from cancer disease suffer from cardiac complications of anticancer treatment, it affects the quality of their lives and life expectancy, especially if the diagnosis is delayed. These patients may present distinct symptoms of cardiac injury, resulting from radiation-induced neurotoxicity and altered pain perception, which makes diagnosis difficult. This review highlights the need for a screening programme for patients who have undergone radiation therapy and which will subsequently have a potentially profound impact on morbidity and mortality.

Gene expression changes in human iPSC-derived cardiomyocytes after X-ray irradiation

Purpose: Radiation-induced heart disease caused by cardiac exposure to ionizing radiation comprises a variety of cardiovascular effects. Research in this field has been hampered by limited availability of clinical samples and appropriate test models. In this study, we wanted to elucidate the molecular mechanisms underlying electrophysiological changes, which we have observed in a previous study. Materials and methods: We employed RNA deep-sequencing of human-induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) 48 h after 5 Gy X-ray irradiation. By comparison to public data from hiPSC-CMs and human myocardium, we verified the expression of cardiac-specific genes in hiPSC-CMs. Results were validated by qRT-PCR. Results: Differentially gene expression analysis identified 39 and 481 significantly up- and down-regulated genes after irradiation, respectively. Besides, a large fraction of genes associated with cell cycle processes, we identified genes implicated in cardiac calcium homeostasis (PDE3B), oxidative stress response (FDXR and SPATA18) and the etiology of cardiomyopathy (SGCD, BBC3 and GDF15). Conclusions: Notably, observed gene expression characteristics specific to hiPSC-CMs might be relevant regarding further investigations of the response to external stressors like radiation. The genes and biological processes highlighted in our study present promising starting points for functional follow-up studies for which hiPSC-CMs could pose an appropriate cell model when cell type specific peculiarities are taken into account.

Model-based cardiac dose estimation in radiation treatment of left breast cancer

OBJECTIVE:

To develop a mathematical model for cardiac dose estimation for patients who have been treated for left-sided breast cancer without CT data.

METHODS:

After obtaining institutional review board approvals, 147 patients with left-sided breast cancer were selected that were treated supine with opposed tangents. The heart blocks from the tangential fields were removed and dose calculations were performed with 6 MV beams using an advanced algorithm. This study was performed with CT data with DRR to represent a radiographic simulator image of yesteryear treatments. The beam's eye-view images showing delineated breast, lung and heart were created to represent views on radiograph. The maximum heart distance (MHD) was recorded and irradiated heart area (AREA) was computed by combination of triangles and rectangles. Based on accurate 3D dose calculation, mean dose (D_mean) and V₁₀ to V₅₀ of heart were analyzed with respect to MHD and AREA for dosimetric parameters using linear and quadratic fit.

RESULTS:

The treatment parameters calculated by MHD and segments using 2D radiographs were within 2% of the actual dosimetric parameters computed from the 3D planning system. The MHD and AREA vs D_mean, V₁₀, V₂₀, V₃₀ and V₅₀ showed very good correlation with linear model (R² > 0.91); however the correlation was significantly better with quadratic model (R² > 0.92). The analysis of the dosimetric error with our linear and quadratic model is remarkable within <3% error for most cases.

CONCLUSION:

The proposed mathematical model for the cardiac dose estimation is accurate within ±3% using a radiograph without CT data. This provides avenues for patient pooling in future studies related to radiation dose and cardiac toxicity. These results will help in estimating cardiac dose analysis accurately from previous studies as well as in centers still using 2D planning.

ADVANCES IN KNOWLEDGE:

The evidence of cardiac risk following radiotherapy continues to be one of the important considerations for the management of left-sided breast cancer patients. One of the problem in the estimation of dose-risk effects is the reconstruction of heart dose for pre-CT treatments. In this study, a simple mathematical model is presented that could estimate cardiac dose within ±3% in left breast cancer treatment from 2D radiograph where CT data do not exist.

Radiation Matters of the Heart: A Mini Review

Radiation Therapy (RT) has been critical in cancer treatment regimens to date. However, it has been shown that ionizing radiation is also associated with increased risk of damage to healthy tissues. At high radiation doses, varied effects including inactivation of cells in treated tissue and associated functional impairment are seen. These range from direct damage to the heart; particularly, diffuse fibrosis of the pericardium and myocardium, adhesion of the pericardium, injury to the blood vessels and stenosis. Cardiac damage is mostly a late responding end-point, occurring anywhere between 1 and 10 years after radiation procedures. Cardiovascular disease following radiotherapy was more common with radiation treatments used before the late 1980s. Modern RT regimens with more focused radiation beams, allow tumors to be targeted more precisely and shield the heart and other healthy tissues for minimizing the radiation damage to normal cells. In this review, we discuss radiation therapeutic doses used and post-radiation damage to the heart muscle from published studies. We also emphasize the need for early detection of cardiotoxicity and the need for more cardio-protection approaches where feasible.

Impact of Ionizing Radiation on Electrophysiological Behavior of Human-induced Ipsc-derived Cardiomyocytes on Multielectrode Arrays

Cardiac arrhythmia presumably induced through cardiac fibrosis is a recurrent long-term consequence of exposure to ionizing radiation. However, there is also evidence that cardiac arrhythmia can occur in patients shortly after irradiation. In this study, the authors employed multielectrode arrays to investigate the short-term effects of x-ray radiation on the electrophysiological behavior of cardiomyocytes derived from human-induced pluripotent stem cells. These cardiomyocytes with spontaneous pacemaker activity were cultured on single-well multielectrode arrays. After exposure to 0, 0.5, 1, 2, 5, 10 Gy x-ray radiation, electrical activity was measured at time points ranging from 10 min to 96 h. RNA sequencing was employed to verify the expression of genes specifically involved in cardiomyocyte differentiation and function. A decrease in beating rate was observed after irradiation with 5 and 10 Gy starting 48 h after exposure. Cells exposed to higher doses of radiation were more prone to show changes in electrophysiological spatial distribution. No radiation-induced effects with respect to the corrected QT interval were detectable. Gene expression analysis showed up regulation of typical cardiac features like ACTC1 or HCN4. In this study, early dose-dependent changes in electrophysiological behavior were determined after x-ray irradiation. Results point towards a dose-dependent effect on pacemaker function of cardiomyocytes and indicate a possible connection between irradiation and short-term changes in electrophysiological cardiac function. Cardiomyocytes derived from human-induced pluripotent stem cells on multielectrode arrays represent a promising in vitro cardiac-modeling system for preclinical studies.

Lung Cancer: Posttreatment Imaging: Radiation Therapy and Imaging Findings

Over the last few decades, advances in radiation therapy technology have markedly improved radiation delivery. Advancements in treatment planning with the development of image-guided radiotherapy and techniques such as proton therapy, allow precise delivery of high doses of radiation conformed to the tumor. These advancements result in improved locoregional control while reducing radiation dose to surrounding normal tissue. The radiologic manifestations of these techniques can differ from radiation induced lung disease seen with traditional radiation therapy. Awareness of these radiologic manifestations and correlation with radiation treatment plans are important to differentiate expected radiation induced lung injury from recurrence, infection and drug toxicity.

Analysis of Irradiated Lung and Heart Volumes using Virtual Simulation in Postoperative Treatment of Stage I Breast Carcinoma

Aims and Background

The aim of the study was to assess the usefulness of virtual simulation in postoperative radiotherapy treatment planning of early-stage breast cancer and to evaluate its potential to reduce the volume of critical structures exposed compared to treatment plans produced by a conventional 2D system.

Methods and Study Design

Eighteen patients undergoing breast radiotherapy following conservative surgery for small breast carcinomas were studied. Scans from spiral CT equipment (with the patient in the treatment position) were transferred to a virtual simulator. From the screen images the operator contoured breast, lung and heart. Calculations were made of the extent to which the heart and lung were included in the irradiation fields (50% isodose line of tangential fields).

Results

Manual contouring was time-consuming, but when virtual simulation was used, the mean volume of the lung included in the radiation fields was significantly reduced compared to the 2D treatment plan (4.5% vs 5.4%, P = 0.034); in addition, a slight reduction was observed for the heart (0.5% to 1.2%), but this was not statistically significant.

Conclusions

With a 3D system we obtained optimal target coverage and a reduction of the dose to critical structures (statistically significant only for the lung). From a clinical point of view, this 0.9% reduction in the mean irradiated lung volume is probably not significant, as the percentage irradiated with a 2D system is considerably below the recommended value. Furthermore, our analysis was performed in a relatively small group of patients; for a reliable estimate larger series would be required. Consequently, the 3D system should not be considered in routine treatment after breast conserving surgery for early stage carcinomas; for the time being it should be reserved for selected cases.

Is Radiation a Risk Factor for Atherosclerosis? An Echo-Color Doppler Study on Hodgkin and Non-Hodgkin Patients

Aims and background

The aim of the present paper was to study the role of irradiation in the atherosclerotic process in patients affected by Hodgkin and non-Hodgkin lymphoma.

Methods

We studied 84 subjects, 42 with Hodgkin or non-Hodgkin disease and 42 controls. All 42 cases had been irradiated and were comparable in terms of risk factors for atherosclerosis. All 84 subjects underwent echo-color Doppler of the arterial axis (carotids, abdominal aorta, and femoral arteries), and the intima-media thickness was measured.

Results

The irradiated cases had a greater intima-media thickness in the carotid district, even after dividing them according to age and sex; males were affected more than females. The irradiated patients were at greater risk of developing cardiovascular events than the controls.

Conclusions

An echo-color Doppler of the carotid district is advisable in all patients who have been submitted to radiotherapy, and the patients with a significantly greater than normal intima-media thickness need a strict follow-up, and antioxidant or antiaggregant therapy should be considered.

Spatial orientation of coronary arteries and its implication for breast and thoracic radiotherapy-proposing "coronary strip" as a new organ at risk

OBJECTIVES

Radiotherapy for breast cancer has been associated with various side effects including cardiac sequelae. Our study aimed to define the spatial arc of spread of coronary vessels in a radian angle.

MATERIALS AND METHODS

We analysed the records of 51 CT coronary angiographies done in our hospital from January 2016 to July 2016. Left anterior descending (LAD) and right coronary (RC) were contoured for each patient. In each axial section, the radial spread of each artery was noted. A 5 mm brush tool was used to join the start and stop angles for making the summated "coronary strips".

RESULTS

Start and end angle of LAD with 95% confidence interval (CI) (in clockwise direction) were 23.9 ± 4° and 79.0 ± 6.6°, respectively. Mean LAD arc length ± SD (standard deviation) noted was 55.1° ± 7.7° (95% CI). For RC the smallest start angle and the largest end angle in all patients was 297.6° and 322.6°, respectively. RC start angle, end angle and arc length for 95% confidence interval were 322.2 ± 6.1°, 292.4 ± 11.6° and 29.8 ± 13.1°, respectively.

CONCLUSIONS

Our study provides a measure of the radial spread of the coronary arteries, especially from the perspective of breast radiotherapy. We have proposed a new organ at risk (OAR) of coronary strip. This should provide an easy and cost-effective way to delineate the coronary vasculature in breast cancer patients undergoing radiotherapy.

Cardio-oncology: conflicting priorities of anticancer treatment and cardiovascular outcome

BACKGROUND

This article about the emerging field of cardio-oncology highlights typical side effects of oncological therapies in the cardiovascular system, cardiovascular complications of malignancies itself, and potential preventive or therapeutic modalities.

METHODS

We performed a selective literature search in PubMed until September 2016.

RESULTS

Cardiovascular events in cancer patients can be frequently attributed to oncological therapies or to the underlying malignancy itself. Furthermore, many patients with cancer have pre-existing cardiovascular diseases that can be aggravated by the malignancy or its therapy. Cardiovascular abnormalities in oncological patients comprise a broad spectrum from alterations in electrophysiological, laboratory or imaging tests to the occurrence of thromboembolic, ischemic or rhythmological events and the impairment of left ventricular function or manifest heart failure.

DISCUSSION

A close interdisciplinary collaboration between oncologists and cardiologists/angiologists as well as an increased awareness of potential cardiovascular complications could improve clinical care of cancer patients and provides a basis for an improved understanding of underlying mechanisms of cardiovascular morbidity.

Quantification of heart, pericardium, and left ventricular myocardium movements during the cardiac cycle for thoracic tumor radiotherapy

Purpose

The purpose of this study was to quantify variations in the heart, pericardium, and left ventricular myocardium (LVM) caused by cardiac movement using the breath-hold technique.

Patients and methods

In this study, the electrocardiography-gated four-dimensional computed tomography (CT) images of 22 patients were analyzed, which were sorted into 20 phases (0-95%) according to the cardiac cycle. The heart, pericardium, and LVM were contoured on each phase of the CT images. The positions, volume, dice similarity coefficient (DSC) in reference to 0% phase, and morphological parameters (max 3D diameter, roundness, spherical disproportion, sphericity, and surface area) in different phases of the heart, pericardium, and LVM were analyzed, which were presented as mean ± standard deviation.

Results

The mean values of displacements along the X, Y, and Z axes respectively were as follows: 1.2 mm, 0.6 mm, and 0.6 mm for the heart; 0.5 mm, 0.4 mm, and 0.8 mm for the pericardium; and 1.0 mm, 4.1 mm, and 1.9 mm for the LVM. The maximum variations in volume and DSC respectively were 16.49%±3.85% and 10.08%±2.14% for the heart, 12.62%±3.94% and 5.20%±1.54% for the pericardium, and 24.23%±11.35% and 184.33%±128.61% for the LVM. The differences in the morphological parameters between the maximum and minimum DSC phases for the heart and pericardium were not significantly different (p>0.05) but were significantly different for the LVM (p<0.05).

Conclusion

The volumetric and morphological variations of the heart were similar to those of pericardium, and all were significantly smaller than those of the LVM. This inconsistency in the volumetric and morphological variations between the LVM and the heart and pericardium indicates that special protection of the LVM should be considered.

Volumetric Modulated Arc (Radio) Therapy in Pets Treatment: The "La Cittadina Fondazione" Experience

Volumetric Modulated Arc Therapy (VMAT) is a modern technique, widely used in human radiotherapy, which allows a high dose to be delivered to tumor volumes and low doses to the surrounding organs at risk (OAR). Veterinary clinics takes advantage of this feature due to the small target volumes and distances between the target and the OAR. Sparing the OAR permits dose escalation, and hypofractionation regimens reduce the number of treatment sessions with a simpler manageability in the veterinary field. Multimodal volumes definition is mandatory for the small volumes involved and a positioning device precisely reproducible with a setup confirmation is needed before each session for avoiding missing the target. Additionally, the elaborate treatment plan must pursue hard constraints and objectives, and its feasibility must be evaluated with a per patient quality control. The aim of this work is to report results with regard to brain meningiomas and gliomas, trigeminal nerve tumors, brachial plexus tumors, adrenal tumors with vascular invasion and rabbit thymomas, in comparison with literature to determine if VMAT is a safe and viable alternative to surgery or chemotherapy alone, or as an adjuvant therapy in pets.

Myocardial stiffness as assessed by diastolic wall strain in adult survivors of childhood leukaemias with preserved left ventricular ejection fraction

Aims

We tested the hypothesis that myocardial stiffness as assessed by diastolic wall strain (DWS) is altered in adult survivors of childhood leukaemias with preserved left ventricular (LV) ejection fraction and explored its association with myocardial fibrosis and diastolic deformation.

Methods and results

Ninety-four (53 males) adult survivors of childhood leukaemias aged 22.2 ± 5.5 years and 66 (36 males) healthy controls were studied retrospectively. Diastolic wall strain and calibrated integrated backscatter (cIB) were measured as indices of myocardial stiffness and fibrosis, respectively. Left and right ventricular (RV) diastolic and torsional mechanics were interrogated using speckle tracking echocardiography. Patients had significantly lower LV DWS, and hence stiffer LV myocardium, and greater myocardial cIB in patients than controls (all P < 0.001). Left ventricular longitudinal, radial, and circumferential early diastolic strain rates, circumferential late diastolic strain rate, and peak twisting and untwisting velocities, tricuspid annular early diastolic velocity, and RV-free wall longitudinal early diastolic strain rate were significantly lower in patients than controls (all P < 0.05). Diastolic wall strain correlated inversely with myocardial cIB, and positively with LV longitudinal, radial, and circumferential early diastolic strain rates (all P < 0.05), while myocardial cIB correlated inversely with LV radial and circumferential early diastolic strain rates, circumferential late diastolic strain rate, peak twisting and untwisting velocities, and tricuspid annular e velocity (all P < 0.05).

Conclusion

In adult survivors of childhood leukaemias, despite the preservation of LV ejection fraction, increased stiffness of the LV myocardium is evident and is associated with myocardial fibrosis and impaired ventricular diastolic function.

Valvular Heart Disease in Cancer Patients: Etiology, Diagnosis, and Management

OPINION STATEMENT

Cardiac valvular disease as consequence of radiation and chemotherapy during treatment for malignancy is growing in its awareness. While the overwhelming emphasis in this population has been on the monitoring and preservation of left ventricular systolic function, we are now developing a greater appreciation for the plethora of cardiac sequelae beyond this basic model. To this end many institutions across the country have developed cardio-oncology programs, which are collaborative practices between oncologists and cardiologists in order to minimize a patient's cardiovascular risk while allowing them to receive the necessary treatment for their cancer. These programs also help to recognize early nuanced treatment complications such as valvular heart disease, and provide consultation for the most appropriate course of action. In this article we will discuss the etiology, prevalence, diagnosis, and current treatment options of valvular heart disease as the result of chemotherapy and radiation.

Spironolactone ameliorates the cardiovascular toxicity induced by concomitant trastuzumab and thoracic radiotherapy

AIM

We aimed to evaluate impact of spironolactone (S) on cardiovascular toxicity of concomitant use of radiotherapy (RT) and trastuzumab (T).

BACKGROUND

S, an aldosterone receptor antagonist, is known to ameliorate the cardiac damage. S ameliorates anthracycline -induced cardiotoxicity, there is no data regarding to effect of S on both T and radiation-induced cardiotoxicity.

MATERIALS/METHODS

Eighty rats were divided into eight groups: group (G) 1 was defined as control group. G2, G3 and G4 were RT, S and T groups respectively. G5, G6, G7 and G8 were RT + T, T + S, RT + S and RT + T + S groups respectively. Rats were sacrificed at 6th hour; 21st and 100th days after RT. Heart and thoracic aorta samples were taken for microscopical examination.

RESULTS

Cardiac inflammation and fibrosis scores and; TGF-β expression were not significantly different within study groups at 6th hour and 21st days of RT. By 100th days of RT fibrosis scores and TGF-β expression in cardiac samples were significantly different between study groups (p values were 0.004 and 0.002 respectively). Pair-wise comparisons revealed that both cardiac fibrosis scores and TGF-β expression levels were higher in G5 when compared to G8 (p values were 0.046 and 0.028 respectively). Moreover the TGF-β expression was higher in G5 when compared to G2 (p = 0.046). We could not demonstrate any significant differences with respect to inflammation, fibrosis and TGF-β expression in thoracic aorta samples between study groups.

CONCLUSIONS

Although S had a protective effect on cardiac tissue it had no protective effect on thoracic aorta when administered with RT + T.

Cardiac Events After Radiation Therapy: Combined Analysis of Prospective Multicenter Trials for Locally Advanced Non-Small-Cell Lung Cancer

Purpose Radiation therapy is a critical component in the care of patients with non-small-cell lung cancer (NSCLC), yet cardiac injury after treatment is a significant concern. Therefore, we wished to elucidate the incidence of cardiac events and their relationship to radiation dose to the heart. Patients and Materials Study eligibility criteria included patients with stage II to III NSCLC treated on one of four prospective radiation therapy trials at two centers from 2004 to 2013. All cardiac events were reviewed and graded per Common Terminology Criteria for Adverse Events (v4.03). The primary end point was the development of a grade ≥ 3 cardiac event. Results In all, 125 patients met eligibility criteria; median follow-up was 51 months for surviving patients. Median prescription dose was 70 Gy, 84% received concurrent chemotherapy, and 27% had pre-existing cardiac disease. Nineteen patients had a grade ≥ 3 cardiac event at a median of 11 months (interquartile range, 6 to 24 months), and 24-month cumulative incidence was 11% (95% CI, 5% to 16%). On multivariable analysis (MVA), pre-existing cardiac disease (hazard ratio [HR], 2.96; 95% CI, 1.07 to 8.21; P = .04) and mean heart dose (HR, 1.07/Gy; 95% CI, 1.02 to 1.13/Gy; P = .01) were significantly associated with grade ≥ 3 cardiac events. Analyzed as time-dependent variables on MVA analysis, both disease progression (HR, 2.15; 95% CI, 1.54 to 3.00) and grade ≥ 3 cardiac events (HR, 1.76; 95% CI, 1.04 to 2.99) were associated with decreased overall survival. However, disease progression (n = 71) was more common than grade ≥ 3 cardiac events (n = 19). Conclusion The 24-month cumulative incidence of grade ≥ 3 cardiac events exceeded 10% among patients with locally advanced NSCLC treated with definitive radiation. Pre-existing cardiac disease and higher mean heart dose were significantly associated with higher cardiac event rates. Caution should be used with cardiac dose to minimize risk of radiation-associated injury. However, cardiac risks should be balanced against tumor control, given the unfavorable prognosis associated with disease progression.

New insight into mitochondrial changes in vascular endothelial cells irradiated by gamma ray

PURPOSE

To investigate alterations of mitochondria in irradiated endothelial cells to further elucidate the mechanism underlying radiation-induced heart disease.

MATERIALS AND METHODS

Experiments were performed using human umbilical vein endothelial cells (HUVECs). HUVECs were irradiated with single gamma ray dose of 0, 5, 10 and 20 Gy, respectively. Apoptosis was assessed by flow cytometry at 24, 48 and 72 h post-irradiation, respectively. The intracellular reactive oxygen species (ROS) was measured with 2',7'-dichlorofluorescein-diacetate (DCFH-DA) at 24 h post-irradiation. Mitochondrial membrane potential (ΔΨm) by JC-1 and the opening of mitochondrial permeability transition pore (mPTP) by a calcein-cobalt quenching method were detected at 24 h post-irradiation in order to measure changes of mitochondria induced by gamma ray irradiation.

RESULTS

Gamma ray irradiation increased HUVECs apoptosis in a dose-dependent and time-dependent manner. Irradiation also promoted ROS production in HUVECs in a dose-dependent manner. At 24 h post-irradiation, the results showed that irradiation decreases ΔΨm, however, paradoxically, flow cytometry showed green fluorescence instensity higher in irradiated HUVECs than in control HUVECs in an irradiation dose-dependent manner which indicated gamma ray irradiation inhibited mPTP opening in HUVECs.

CONCLUSIONS

Gamma ray irradiation induces apoptosis and ROS production of endothelial cells, and decreases ΔΨm meanwhile contradictorily inhibiting the opening of mPTP.

Assessment of concomitant versus sequential trastuzumab on radiation-induced cardiovascular toxicity

There are limited data regarding effect of trastuzumab on radiation-induced cardiovascular toxicity when used sequentially or concomitantly. This experimental study aims to investigate effect of trastuzumab on radiation-induced cardiovascular toxicity with respect to the treatment sequence. One hundred and eight female Wistar albino rats were divided into six groups (G): G1 was control, G2 was trastuzumab, and G3 was radiotherapy (RT); G4 and G6 were sequential RT and trastuzumab; and G5 was concomitant RT and trastuzumab groups, respectively. Rats were killed at 6th h, 21st and 70th days after RT; thoracic aorta and heart samples were obtained. Transthoracic echocardiography and functional studies evaluating relaxation of thoracic aorta were performed. Subendothelial edema scores of thoracic aorta samples at 21st and 70th days were higher in RT groups (G3, G4, G5, and G6) ( p < 0.001). There was a deterioration of relaxation responses of thoracic aorta samples in RT groups ( p < 0.001). Cardiac fibrosis (CF) scores revealed detrimental effect of RT beginning from 6th h and trastuzumab from 21st day. RT groups showed further deterioration of CF at 70th day. Ejection fraction, left ventricular mass, and fractional shortening were significantly decreased in G4, G5, and G6. Trastuzumab may increase pathological damage in cardiovascular structures when used with RT regardless of timing.

Radiobiology in Cardiovascular Imaging

The introduction of ionizing radiation in medicine revolutionized the diagnosis and treatment of disease and dramatically improved and continues to improve the quality of health care. Cardiovascular imaging and medical imaging in general, however, are associated with a range of radiobiologic effects, including, in rare instances, moderate to severe skin damage resulting from cardiac fluoroscopy. For the dose range associated with diagnostic imaging (corresponding to effective doses on the order of 10 mSv [1 rem]), the possible effects are stochastic in nature and largely theoretical. The most notable of these effects, of course, is the possible increase in cancer risk. The current review addresses radiobiology relevant to cardiovascular imaging, with particular emphasis on radiation induction of cancer, including consideration of the linear nonthreshold dose-response model and of alternative models such as radiation hormesis.

Quantification of coronary artery motion and internal risk volume from ECG gated radiotherapy planning scans

BACKGROUND

Radiotherapy for carcinoma of breast and thoracic structures involves inadvertent radiation to heart and coronary arteries (CA). Coronary artery stenosis in high radiation dose segments has been documented. Cardiac and respiratory motion induced displacement of CA and internal risk volume (IRV) margin remains inadequately quantified.

MATERIAL AND METHODS

Twenty cases of carcinoma breast, lung and lung metastasis were enrolled in this study. ECG gated intravenous contrast enhanced computed tomography (CECT) scans were performed in inspiratory breath hold (IBH) and expiratory breath hold (EBH). The images were segregated into inspiratory systole (IS), inspiratory diastole (ID), expiratory systole (ES) and expiratory diastole (ED) sets. Left anterior descending (LAD), limited segment of LAD close to chest wall (short LAD), right coronary artery (RCA), Left circumflex artery (LCX) and left ventricle (LV) were delineated in all four sets. Mean displacements in systole versus diastole and inspiration versus expiration were calculated in three co-ordinates [anterio-posterior (Z), left-right (X) and cranio-caudal (Y)].

RESULTS

Mean of displacement (mm) between systole and diastole (IS versus ID; and ES versus ED) in X, Y, Z co-ordinates were: LAD 3.0(±1.6), 2.8(±1.5), 3.6(±2.0); Short-LAD 3.0(±1.1), 0.8(±0.4), 2.4(±0.6); LV 2.4(±1.6), 1.7(±1), 5.0(±1.5); LCX 4.9(±1.6), 2.9(±1.3), 5.1(±1.9); RCA 6.6(±2.2), 3.6(±2.1), 5.9(±2.2). Mean displacement between inspiration and expiration (IS versus ES; and ID versus ED) in X, Y, Z axes were: LAD 3.3(±1.5), 8.0(±3.4), 3.8(±1.8); Short-LAD 2.7(±1), 12.2(±4.4), 3.3(±1.5); LV 2.9(±1.4), 9.8(±3.3), 4.7(±1.9); LCX 2.9(±.8), 9.7(±3.2), 6.2(±2.5); RCA 2.6(±1.3), 7.6(±2.5), 3.8(±1.7).

CONCLUSION

Radial (RM), cranio-caudal margin (CC) of 7mm, 4mm in breath-hold radiotherapy whereas RM, CC of 7mm, 13mm respectively in free breath radiotherapy will cover the range of motions of CA, LV and can be recommended as IRV for these structures.

The use of concurrent hormonotherapy and radiotherapy does not deteriorate radiation-induced cardiac toxicity

Postmenopausal patients with breast cancer have two options for adjuvant endocrine therapy, tamoxifen and aromatase inhibitors (AIs) as well as radiotherapy (RT) and chemotherapy. However, there is limited data regarding the optimal sequencing of RT and tamoxifen/AIs. Thus, we aimed to evaluate the effects of tamoxifen and AIs on radiation-induced cardiotoxicity. Eighty ovariectomized rats were divided into eight groups (G). G1 was defined as a control group; G2, G3, G4, and G5 were RT, tamoxifen, anastrozle, and letrozole groups, respectively; G6, G7, and G8 were RT plus tamoxifen, anastrozle, and letrozole groups, respectively. Drugs were started 1 week before RT and continued until the animals were killed 16 weeks after RT. The heart tissues were then dissected and examined with light microscopy to determine endocardial thickness and cardiac fibrosis. The endocardial thickness scores of both RT alone and the tamoxifen groups as well as the cardiac fibrosis score of RT alone were higher than that the control group ( p < 0.05 for all). There was no difference in the endocardial thickness and cardiac fibrosis scores of the RT-only group and the RT plus hormonotherapy groups ( p > 0.05 for all). Concurrent administration of RT and hormonal therapy with either tamoxifen or AIs did not further amplify radiation-induced cardiac toxicity. This issue warrants further study.

Radiation dose distribution in coronary arteries in breast cancer radiotherapy

BACKGROUND

Women irradiated for left-sided breast cancer (BC) have an increased risk of coronary artery disease compared to women with right-sided BC. We describe the distribution of radiation dose in segments of coronary arteries in women receiving adjuvant radiotherapy (RT) for left- or right-sided BC.

MATERIAL AND METHODS

Fifteen women with BC, seven left-sided and eight right-sided, who had received three-dimensional conformal radiotherapy (3DCRT), constituted the study base. The heart and the segments of the coronary arteries were defined as separate organs at risk (OAR), and the mean and maximum radiation doses were calculated for each OAR.

RESULTS

In women with left-sided BC, irrespective of if regional lymph node RT was given or not, maximum dose in mid and distal left anterior descending artery (mdLAD) was approximately 50 Gy in 6/7 patients, whereas women with right-sided BC mainly received low doses of radiation. In women with left-sided BC, 6/7 patients had substantially higher mean dose to the distal LAD than to the heart, ranging from 30 to 55 Gy and 3 to13 Gy, respectively.

CONCLUSION

We found a pronounced difference of radiation dose distribution in the coronary arteries between women with left- and right-sided BC. Women with left-sided BC had almost full treatment dose in parts of mdLAD, regardless of if regional lymph node irradiation was given or not, while women with right-sided BC mainly received low doses to the coronary arteries.

Cardio-Oncology: An Update on Cardiotoxicity of Cancer-Related Treatment

Through the success of basic and disease-specific research, cancer survivors are one of the largest growing subsets of individuals accessing the healthcare system. Interestingly, cardiovascular disease is the second leading cause of morbidity and mortality in cancer survivors after recurrent malignancy. This recognition has helped stimulate a collaboration between oncology and cardiology practitioners and researchers, and the portmanteau cardio-oncology (also known as onco-cardiology) can now be found in many medical centers. This collaboration promises new insights into how cancer therapies impact cardiovascular homeostasis and long-term effects on cancer survivors. In this review, we will discuss the most recent views on the cardiotoxicity related to various classes of chemotherapy agents and radiation. We will also discuss broadly the current strategies for treating and preventing cardiovascular effects of cancer therapy.

Late Effects of Total-Body Gamma Irradiation on Cardiac Structure and Function in Male Rhesus Macaques

Heart disease is an increasingly recognized, serious late effect of radiation exposure, most notably among breast cancer and Hodgkin's disease survivors, as well as the Hiroshima and Nagasaki atomic bomb survivors. The purpose of this study was to evaluate the late effects of total-body irradiation (TBI) on cardiac morphology, function and selected circulating biomarkers in a well-established nonhuman primate model. For this study we used male rhesus macaques that were exposed to a single total-body dose of ionizing gamma radiation (6.5-8.4 Gy) 5.6-9.7 years earlier at ages ranging from ∼3-10 years old and a cohort of nonirradiated controls. Transthoracic echocardiography was performed annually for 3 years on 20 irradiated and 11 control animals. Myocardium was examined grossly and histologically, and myocardial fibrosis/collagen was assessed microscopically and by morphometric analysis of Masson's trichrome-stained sections. Serum/plasma from 27 irradiated and 13 control animals was evaluated for circulating biomarkers of cardiac damage [N-terminal pro B-type natriuretic protein (nt-proBNP) and troponin-I], inflammation (CRP, IL-6, MCP-1, sICAM) and microbial translocation [LPS-binding protein (LBP) and sCD14]. A higher prevalence of histological myocardial fibrosis was observed in the hearts obtained from the irradiated animals (9/14) relative to controls (0/3) (P = 0.04, χ(2)). Echocardiographically determined left ventricular end diastolic and systolic diameters were significantly smaller in irradiated animals (repeated measures ANOVA, P < 0.001 and P < 0.008, respectively). Histomorphometric analysis of trichrome-stained sections of heart tissue demonstrated ∼14.9 ± 1.4% (mean ± SEM) of myocardial area staining for collagen in irradiated animals compared to 9.1 ± 0.9 % in control animals. Circulating levels of MCP-1 and LBP were significantly higher in irradiated animals (P < 0.05). A high incidence of diabetes in the irradiated animals was associated with higher plasma triglyceride and lower HDLc but did not appear to be associated with cardiovascular phenotypes. These results demonstrate that single total-body doses of 6.5-8.4 Gy produced long-term effects including a high incidence of myocardial fibrosis, reduced left ventricular diameter and elevated systemic inflammation. Additional prospective studies are required to define the time course and mechanisms underlying radiation-induced heart disease in this model.

Detection of late radiation damage on left atrial fibrosis using cardiac late gadolinium enhancement magnetic resonance imaging

Purpose

This is a proof-of-principle study investigating the feasibility of using late gadolinium enhancement magnetic resonance imaging (LGE-MRI) to detect left atrium (LA) radiation damage.

Methods and materials

LGE-MRI data were acquired for 7 patients with previous external beam radiation therapy (EBRT) histories. The enhancement in LA scar was delineated and fused to the computed tomography images used in dose calculation for radiation therapy. Dosimetric and normal tissue complication probability analyses were performed to investigate the relationship between LA scar enhancement and radiation doses.

Results

The average LA scar volume for the subjects was 2.5 cm³ (range, 1.2-4.1 cm³; median, 2.6 cm³). The overall average of the mean dose to the LA scar was 25.9 Gy (range, 5.8-49.2 Gy). Linear relationships were found between the amount of radiation dose (mean dose) (R² = 0.8514, P = .03) to the LA scar-enhanced volume. The ratio of the cardiac tissue change (LA scar/LA wall) also demonstrated a linear relationship with the level of radiation received by the cardiac tissue (R² = 0.9787, P < .01). Last, the normal tissue complication probability analysis suggested a dose response function to the LA scar enhancement.

Conclusions

With LGE-MRI and 3-dimensional dose mapping on the treatment planning system, it is possible to define subclinical cardiac damage and distinguish intrinsic cardiac tissue change from radiation induced cardiac tissue damage. Imaging myocardial injury secondary to EBRT using MRI may be a useful modality to follow cardiac toxicity from EBRT and help identify individuals who are more susceptible to EBRT damage. LGE-MRI may provide essential information to identify early screening strategy for affected cancer survivors after EBRT treatment.