Radiation-related heart disease: current knowledge and future prospects

Embryonic ionizing radiation exposure results in expression alterations of genes associated with cardiovascular and neurological development, function, and disease and modified cardiovascular function in zebrafish

The relationship between ionizing radiation (IR) and carcinogenesis is long established, but recently the association between IR and other diseases is starting to be recognized. Currently, there is limited information on the genetic mechanisms governing the role of IR in non-cancer related adverse health effects and in regards to an early developmental exposure. In this study, zebrafish embryos were exposed to a range of IR doses (0, 1, 2, 5, 10 Gy) at 26 h post fertilization (hpf). No significant increase in mortality or hatching rate was observed, but a significant decrease in total larval length, head length, and eye diameter was observed in the 10 Gy dose. Transcriptomic analysis was conducted at 120 hpf to compare gene expression profiles between the control and highest IR dose at which no significant differences were observed in morphological measurements (5 Gy). 253 genes with well-established function or orthology to human genes were significantly altered. Gene ontology and molecular network analysis revealed enrichment of genes associated with cardiovascular and neurological development, function, and disease. Expression of a subset of genetic targets with an emphasis on those associated with the cardiovascular system was assessed using Quantitative PCR (qPCR) to confirm altered expression at 5 Gy and then to investigate alterations at lower doses (1 and 2 Gy). Strong correlation between microarray and qPCR expression values was observed, but zebrafish exposed to 1 or 2 Gy resulted in a significant expression alteration in only one of these genes (LIN7B). Moreover, heart rate was analyzed through 120 hpf following IR dosing at 26 hpf. A significant decrease in heart rate was observed at 10 Gy, while a significant increase in heart rate was observed at 1, 2, and 5 Gy. Overall these findings indicate IR exposure at doses below those that induce gross morphological changes alters heart rate and expression of genes associated with cardiovascular and neurological functions.

Cardiac counterclockwise rotation is a risk factor for high-dose irradiation to the left anterior descending coronary artery in patients with left-sided breast cancer who receiving adjuvant radiotherapy after breast-conserving surgery

Patients irradiated for left-sided breast cancer have higher incidence of cardiovascular disease than those receiving irradiation for right-sided breast cancer. Most abnormalities were in the left anterior descending (LAD) coronary artery territory. We analyzed the relationships between preoperative examination results and irradiation dose to the LAD artery in patients with left-sided breast cancer. Seventy-one patients receiving breast radiotherapy were analyzed. The heart may rotate around longitudinal axis, showing either clockwise or counterclockwise rotation (CCWR). On electrocardiography, the transition zone (TZ) was judged in precordial leads. CCWR was considered to be present if TZ was at or to the right of V3. The prescribed dose was 50 Gy in 25 fractions. The maximum (Dmax) and mean (Dmean) doses to the LAD artery and the volumes of the LAD artery receiving at least 20 Gy, 30 Gy and 40 Gy (V20Gy, V30Gy and V40Gy, respectively) were significantly higher in CCWR than in the non-CCWR patients. On multivariate analysis, TZ was significantly associated with Dmax, Dmean, V20Gy, V30Gy, and V40Gy. CCWR is a risk factor for high-dose irradiation to the LAD artery. Electrocardiography is useful for evaluating the cardiovascular risk of high-dose irradiation to the LAD artery.

Sparing functional anatomical structures during intensity-modulated radiotherapy: an old problem, a new solution

ABSTRACT During intensity-modulated radiotherapy, an organ is usually assumed to be functionally homogeneous and, generally, its anatomical and spatial heterogeneity with respect to radiation response are not taken into consideration. However, advances in imaging and radiation techniques as well as an improved understanding of the radiobiological response of organs have raised the possibility of sparing the critical functional structures within various organs at risk during intensity-modulated radiotherapy. Here, we discuss these structures, which include the critical brain structure, or neural nuclei, and the nerve fiber tracts in the CNS, head and neck structures related to radiation-induced salivary and swallowing dysfunction, and functional structures in the heart and lung. We suggest that these structures can be used as potential surrogate organs at risk in order to minimize their radiation dose and/or irradiated volume without compromising the dose coverage of the target volume during radiation treatment.

A case of chemoradiotherapy-associated cardiotoxicity that developed into acute heart failure with progressive subendocardial fibrosis

We describe the case of a 61-year-old Japanese woman who developed acute heart failure 5 years after chemoradiotherapy for breast cancer. The patient received less than the cardiotoxic dose of docetaxel, epirubicin, cyclophosphamide, and fluorouracil and experienced no cardiovascular complications in the 5 years between the onset of chemoradiotherapy and the onset of acute heart failure. Cardiac catheterization was performed and elevation of end diastolic pressure of both ventricles was observed. Endomyocardial biopsy showed progressive replacement fibrosis in the subendocardium. Normal thickness of the right endocardium is <20 μm. Surprisingly, our patient had a fibrous subendocardium that was 100-200 μm thick. Ultrastructural abnormalities similar to those observed in anthracycline cardiotoxicity were evident on electron micrographs. This case report demonstrates the unique pathophysiology of heart failure in a patient who received less than the cardiotoxic dose of antineoplastic agents. Recent protocols have decreased the dosage of cardiotoxic agents; however, even these reduced doses might not be safe for all Japanese individuals and may cause subclinical cardiovascular damage and late-onset heart failure. Clinicians should monitor cancer survivors carefully, even if antineoplastic agents were administered under the cardiotoxic dose. <Learning objective: Intensive chemotherapy is commonly used to treat cancer patients. Recent protocols have decreased the dose of cardiotoxic agents; however, even these reduced doses might not be safe and may cause subclinical cardiovascular damage and late-onset heart failure. Clinicians should monitor cancer survivors carefully, even if antineoplastic agents were administered under the toxic dose.>.

Stem cell therapies for the treatment of radiation-induced normal tissue side effects

SIGNIFICANCE

Targeted irradiation is an effective cancer therapy but damage inflicted to normal tissues surrounding the tumor may cause severe complications. While certain pharmacologic strategies can temper the adverse effects of irradiation, stem cell therapies provide unique opportunities for restoring functionality to the irradiated tissue bed.

RECENT ADVANCES

Preclinical studies presented in this review provide encouraging proof of concept regarding the therapeutic potential of stem cells for treating the adverse side effects associated with radiotherapy in different organs. Early-stage clinical data for radiation-induced lung, bone, and skin complications are promising and highlight the importance of selecting the appropriate stem cell type to stimulate tissue regeneration.

CRITICAL ISSUES

While therapeutic efficacy has been demonstrated in a variety of animal models and human trials, a range of additional concerns regarding stem cell transplantation for ameliorating radiation-induced normal tissue sequelae remain. Safety issues regarding teratoma formation, disease progression, and genomic stability along with technical issues impacting disease targeting, immunorejection, and clinical scale-up are factors bearing on the eventual translation of stem cell therapies into routine clinical practice.

FUTURE DIRECTIONS

Follow-up studies will need to identify the best possible stem cell types for the treatment of early and late radiation-induced normal tissue injury. Additional work should seek to optimize cellular dosing regimes, identify the best routes of administration, elucidate optimal transplantation windows for introducing cells into more receptive host tissues, and improve immune tolerance for longer-term engrafted cell survival into the irradiated microenvironment.

Radiotherapy and anthracyclines - cardiovascular toxicity

The subject of this paper is to analyze the impact of radiotherapy and anthracyclines on the cardiovascular system, based on a survey of contemporary literature. Currently, high efficiency of anticancer therapies has increased the rate of survival in patients treated for cancer. It should be emphasized, however, that these treatments damage not only the affected but also the healthy tissue. Consequently, with the increase of survival rate in these patients, the number of patients with complaints regarding numerous organs and systems also increases as a result of earlier treatment. Thus, during the first decade of the 21^st century, a number of concerns about the relationship between cancer treatment and dysfunction of the cardiovascular system were resolved. Anthracyclines, as well as radiotherapy, are capable of damaging the cardiovascular system, both at the central level, by the deterioration of cardiac function, and at peripheral levels, by increasing the hemodynamic and thrombotic changes.

Allogenic cardiomyoblasts raised from human mesenchymal stem cells in the therapy of radiation cardiomyopathy and pericarditis: case report

The use of triple systemic transplantation of cardiomyoblasts raised from the culture of allogenic bone marrow mesenchymal stem cells of a healthy donor according to the new medical technology licensed by Federal Service on Surveillance in Healthcare in the therapy of a patient with late radiation cardiomyopathy and radiation exudative pericarditis developed 45 years after radiation therapy for Hodgkin lymphoma. High efficiency of systemic transplantation of mesenchymal stem cells partially differentiated towards cardiomyocytes was demonstrated. The therapeutic effect persists for more than 2 years. Possible mechanisms of the therapeutic effect of this type of stem cells and the prospects of using cell therapy in the treatment of late radiation injuries of vital organs and tissues are discussed.

Mitigating the risk of radiation-induced cancers: limitations and paradigms in drug development

The United States radiation medical countermeasures (MCM) programme for radiological and nuclear incidents has been focusing on developing mitigators for the acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE), and biodosimetry technologies to provide radiation dose assessments for guiding treatment. Because a nuclear accident or terrorist incident could potentially expose a large number of people to low to moderate doses of ionising radiation, and thus increase their excess lifetime cancer risk, there is an interest in developing mitigators for this purpose. This article discusses the current status, issues, and challenges regarding development of mitigators against radiation-induced cancers. The challenges of developing mitigators for ARS include: the long latency between exposure and cancer manifestation, limitations of animal models, potential side effects of the mitigator itself, potential need for long-term use, the complexity of human trials to demonstrate effectiveness, and statistical power constraints for measuring health risks (and reduction of health risks after mitigation) following relatively low radiation doses (<0.75 Gy). Nevertheless, progress in the understanding of the molecular mechanisms resulting in radiation injury, along with parallel progress in dose assessment technologies, make this an opportune, if not critical, time to invest in research strategies that result in the development of agents to lower the risk of radiation-induced cancers for populations that survive a significant radiation exposure incident.

Cardiovascular disease after cancer therapy

Improvements in treatment and earlier diagnosis have both contributed to increased survival for many cancer patients. Unfortunately, many treatments carry a risk of late effects including cardiovascular diseases (CVDs), possibly leading to significant morbidity and mortality. In this paper we describe current knowledge of the cardiotoxicity arising from cancer treatments, outline gaps in knowledge, and indicate directions for future research and guideline development, as discussed during the 2014 Cancer Survivorship Summit organised by the European Organisation for Research and Treatment of Cancer (EORTC). Better knowledge is needed of the late effects of modern systemic treatments and of radiotherapy to critical structures of the heart, including the effect of both radiation dose and volume of the heart exposed. Research elucidating the extent to which treatments interact in causing CVD, and the mechanisms involved, as well as the extent to which treatments may increase CVD indirectly by increasing cardiovascular risk factors is also important. Systematic collection of data relating treatment details to late effects is needed, and great care is needed to obtain valid and generalisable results. Better knowledge of these cardiac effects will contribute to both primary and secondary prevention of late complications where exposure to cardiotoxic treatment is unavoidable. Also surrogate markers would help to identify patients at increased risk of cardiotoxicity. Evidence-based screening guidelines for CVD following cancer are also needed. Finally, risk prediction models should be developed to guide primary treatment choice and appropriate follow up after cancer treatment.

Advanced radiotherapy techniques for breast cancer to minimize cardiovascular risk

SUMMARY 

Radiotherapy plays an integral role in the management of breast cancer and has been demonstrated to reduce the risk of recurrence and improve overall survival. Recent reports in the literature have suggested a dose-dependent risk of cardiovascular disease following radiation treatment for breast cancer. This article highlights new advances in radiotherapy for breast cancer that may help minimize radiotherapy doses to the heart.

Expert consensus for multi-modality imaging evaluation of cardiovascular complications of radiotherapy in adults: a report from the European Association of Cardiovascular Imaging and the American Society of Echocardiography

Cardiac toxicity is one of the most concerning side effects of anti-cancer therapy. The gain in life expectancy obtained with anti-cancer therapy can be compromised by increased morbidity and mortality associated with its cardiac complications. While radiosensitivity of the heart was initially recognized only in the early 1970s, the heart is regarded in the current era as one of the most critical dose-limiting organs in radiotherapy. Several clinical studies have identified adverse clinical consequences of radiation-induced heart disease (RIHD) on the outcome of long-term cancer survivors. A comprehensive review of potential cardiac complications related to radiotherapy is warranted. An evidence-based review of several imaging approaches used to detect, evaluate, and monitor RIHD is discussed. Recommendations for the early identification and monitoring of cardiovascular complications of radiotherapy by cardiac imaging are also proposed.

Assessing cardiac injury in mice with dual energy-microCT, 4D-microCT, and microSPECT imaging after partial heart irradiation

PURPOSE

To develop a mouse model of cardiac injury after partial heart irradiation (PHI) and to test whether dual energy (DE)-microCT and 4-dimensional (4D)-microCT can be used to assess cardiac injury after PHI to complement myocardial perfusion imaging using micro-single photon emission computed tomography (SPECT).

METHODS AND MATERIALS

To study cardiac injury from tangent field irradiation in mice, we used a small-field biological irradiator to deliver a single dose of 12 Gy x-rays to approximately one-third of the left ventricle (LV) of Tie2Cre; p53(FL/+) and Tie2Cre; p53(FL/-) mice, where 1 or both alleles of p53 are deleted in endothelial cells. Four and 8 weeks after irradiation, mice were injected with gold and iodinated nanoparticle-based contrast agents, and imaged with DE-microCT and 4D-microCT to evaluate myocardial vascular permeability and cardiac function, respectively. Additionally, the same mice were imaged with microSPECT to assess myocardial perfusion.

RESULTS

After PHI with tangent fields, DE-microCT scans showed a time-dependent increase in accumulation of gold nanoparticles (AuNp) in the myocardium of Tie2Cre; p53(FL/-) mice. In Tie2Cre; p53(FL/-) mice, extravasation of AuNp was observed within the irradiated LV, whereas in the myocardium of Tie2Cre; p53(FL/+) mice, AuNp were restricted to blood vessels. In addition, data from DE-microCT and microSPECT showed a linear correlation (R(2) = 0.97) between the fraction of the LV that accumulated AuNp and the fraction of LV with a perfusion defect. Furthermore, 4D-microCT scans demonstrated that PHI caused a markedly decreased ejection fraction, and higher end-diastolic and end-systolic volumes, to develop in Tie2Cre; p53(FL/-) mice, which were associated with compensatory cardiac hypertrophy of the heart that was not irradiated.

CONCLUSIONS

Our results show that DE-microCT and 4D-microCT with nanoparticle-based contrast agents are novel imaging approaches complementary to microSPECT for noninvasive assessment of the change in myocardial vascular permeability and cardiac function of mice in whom myocardial injury develops after PHI.

Comorbidities and cardiovascular disease risk in older breast cancer survivors

OBJECTIVE

To evaluate cardiovascular disease (CVD) risk factors in older breast cancer survivors compared with a group of women without breast cancer.

STUDY DESIGN

The retrospective study included (1) women aged 65 or more years who were initially diagnosed with stage I or II breast cancer from 1990 to 1994 in 6 US health plans and who survived at least 5 years post-diagnosis (cases) and (2) a matched comparison group. They were followed for a maximum of 15 years.

METHODS

Data sources included medical charts and electronic health records. Cases (n = 1361) were matched on age, health plan site, and enrollment year to women in the comparison group (n = 1361). Subjects were followed to the first CVD outcome, health plan disenrollment, death, or study end. We compared rates of CVD in these 2 groups and used Cox proportional hazard models to estimate the hazard ratio (HR), considering body mass index, smoking history, diabetes, and hypertension.

RESULTS

The strongest predictors of CVD were smoking history (HR = 1.29; 95% confidence interval [CI], 1.15-1.46), diabetes (HR = 1.72; 95% CI, 1.48-1.99), and hypertension (HR = 1.48; 95% CI, 1.31-1.67) rather than breast cancer case-comparison status (HR = 0.97; 95% CI, 0.87-1.09).

CONCLUSION

Results suggest that long-term prognosis in breast cancer patients is affected by management of preexisting conditions. Assessment of comorbid conditions and effective management of diabetes and hypertension in older breast cancer survivors may lead to longer overall survival.

Potential increased risk of ischemic heart disease mortality with significant dose fractionation in the Canadian Fluoroscopy Cohort Study

Risks of noncancer causes of death, particularly cardiovascular disease, associated with exposures to high-dose ionizing radiation, are well known. Recent studies have reported excess risk in workers who are occupationally exposed to low doses at a low dose rate, but the risks of moderately fractionated exposures, such as occur during diagnostic radiation procedures, remain unclear. The Canadian Fluoroscopy Cohort Study includes 63,707 tuberculosis patients exposed to multiple fluoroscopic procedures in 1930-1952 and followed-up for death from noncancer causes in 1950-1987. We used a Poisson regression to estimate excess relative risk (ERR) per Gy of cumulative radiation dose to the lung (mean dose = 0.79 Gy; range, 0-11.60). The risk of death from noncancer causes was significantly lower in these subjects compared with the Canadian general population (P < 0.001). We estimated small, nonsignificant increases in the risk of death from noncancer causes with dose. We estimated an ERR/Gy of 0.176 (95% confidence interval: 0.011, 0.393) (n = 5,818 deaths) for ischemic heart disease (IHD) after adjustment for dose fractionation. A significant (P = 0.022) inverse dose fractionation effect in dose trends of IHD was observed, with the highest estimate of ERR/Gy for those with the fewest fluoroscopic procedures per year. Radiation-related risks of IHD decreased significantly with increasing time since first exposure and age at first exposure (both P < 0.05). This is the largest study of patients exposed to moderately fractionated low-to-moderate doses of radiation, and it provides additional evidence of increased radiation-associated risks of death from IHD, in particular, significantly increased radiation risks from doses similar to those from diagnostic radiation procedures. The novel finding of a significant inverse dose-fractionation association in IHD mortality requires further investigation.

Expert consensus for multi-modality imaging evaluation of cardiovascular complications of radiotherapy in adults: a report from the European Association of Cardiovascular Imaging and the American Society of Echocardiography

Cardiac toxicity is one of the most concerning side effects of anti-cancer therapy. The gain in life expectancy obtained with anti-cancer therapy can be compromised by increased morbidity and mortality associated with its cardiac complications. While radiosensitivity of the heart was initially recognized only in the early 1970s, the heart is regarded in the current era as one of the most critical dose-limiting organs in radiotherapy. Several clinical studies have identified adverse clinical consequences of radiation-induced heart disease (RIHD) on the outcome of long-term cancer survivors. A comprehensive review of potential cardiac complications related to radiotherapy is warranted. An evidence-based review of several imaging approaches used to detect, evaluate, and monitor RIHD is discussed. Recommendations for the early identification and monitoring of cardiovascular complications of radiotherapy by cardiac imaging are also proposed.

The feasibility of evaluating radiation dose to the heart by integrating kilovoltage-cone beam computed tomography in stereotactic body radiotherapy of early non-small-cell lung cancer patients

BACKGROUND

To investigate the feasibility of contouring the planning risk organ volume (PRV) for the heart, and to determine the probability of evaluating radiation dose to the heart using kilovoltage-cone beam computed tomography (kV-CBCT) in early-stage non-small-cell lung cancer (NSCLC) patients, who received stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

Seventeen NSCLC patients who received SBRT (5Gy/f × 10f dose) were enrolled and subjected to CBCT and CT imaging analyses to plan treatment. Sequential planning CBCT images of individual patient's hearts were analyzed for reproducibility of heart contouring and volume. Comparative analyses were made between the planning CT- and CBCT-detected heart margins and dose-volume indices for treatment.

RESULTS

The heart volume from planning CT images was significantly smaller than that from CBCT scans (p < 0.05), and the volumes based on the different series of CBCT images were similar (p > 0.05).The overlap of the heart region on the same anatomical section between the first series of CBCT scans and other scans reached 0.985 ± 0.020 without statistically significant differences (p > 0.05). The mean margins of the heart from planning CT and CBCT scans were 10.5 ± 2.8 mm in the left direction, 5.9 ± 2.8 mm in the right direction, 2.2 ± 1.6 mm in the direction of the head, 3.3 ± 2.2 mm in the direction of the foot, 6.7 ± 1.1 mm in the anterior direction, and 4.5 mm ± 2.5 mm in the posterior direction. All relative and absolute dose-volume indices obtained from CBCT images were significantly larger than those from planning CT scans (p < 0.05), with the exception of the volume in the 5Gy region.

CONCLUSION

The PRV of heart contouring based on kV-CBCT is feasible with good reproducibility. More accurate and objective dose-volume indices may be obtained for NSCLC patients by using kV-CBCT, instead of CT, to plan SBRT.

Outcome after ST elevation myocardial infarction in patients with cancer treated with primary percutaneous coronary intervention

The simultaneous occurrence of cancer and coronary heart disease is increasing in the Western world. Nevertheless, the influence of cancer on ST elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) has not been investigated extensively. This multicenter registry included patients with STEMI treated with primary PCI from 2006 to 2009. Patients were stratified according to history of cancer, and primary focus lay on all-cause and cardiac mortalities during 1-year follow-up. Adjusted effect sizes were calculated using Cox proportional hazard models. In total, 208 patients had a history of cancer (diagnosed ≤6 months ago in 20.7%, 6 months to 3 years ago in 21.7%, and >3 years ago in 57.6%) and 3,215 patients had no history of cancer. Chemotherapy had been administered previously to 23% of patients with cancer. Patients with cancer were older, more frequently women, and more commonly known with previous myocardial infarction or anemia. Reperfusion rates were similar after PCI. Patients with cancer showed greater all-cause (17.4% vs 6.5% in other patients) and cardiac mortalities at 1 year (10.7% vs 5.4% in other patients) because of high early cardiac death (23.8%) in recently diagnosed patients with cancer. After adjustment, a recent cancer diagnosis predicted cardiac mortality at 7 days (hazard ratio 3.34, 95% confidence interval 1.57 to 7.08). The adverse prognosis was partly explained by anemia and occurrence of cardiogenic shock, whereas outcome was independent of cancer treatment. In conclusion, patients with cancer showed greater mortality after STEMI. A cancer diagnosis in the 6 months before primary PCI was strongly associated with early cardiac mortality.

Role of DNA damage in cardiovascular disease

Patients with some progeroid syndromes, such as Werner syndrome, exhibit atherosclerotic cardiovascular disease (CVD) at a young age as a manifestation of premature aging. Recent studies have revealed that most progeroid syndromes are caused by genetic defects in specific molecules involved in the DNA damage response, a cornerstone of genome stability. Ionizing radiation is one of the most potent genotoxic stimuli and causes various kinds of DNA damage. Further, there is increasing evidence that therapeutic radiation treatments can cause cardiovascular complications. Here, we describe the DNA damage and subsequent response, review recent advances in the understanding of the molecular basis of progeroid syndromes (especially those syndromes that involve CVD), review the pathological and epidemiological analysis of radiation-induced CVD, and discuss the possible role of DNA damage and the DNA damage response in the pathogenesis of atherosclerotic CVD.

Monte Carlo calculated doses to treatment volumes and organs at risk for permanent implant lung brachytherapy

Iodine-125 ((125)I) and Caesium-131 ((131)Cs) brachytherapy have been used with sublobar resection to treat stage I non-small cell lung cancer and other radionuclides, (169)Yb and (103)Pd, are considered for these treatments. This work investigates the dosimetry of permanent implant lung brachytherapy for a range of source energies and various implant sites in the lung. Monte Carlo calculated doses are calculated in a patient CT-derived computational phantom using the EGsnrc user-code BrachyDose. Calculations are performed for (103)Pd, (125)I, (131)Cs seeds and 50 and 100 keV point sources for 17 implant positions. Doses to treatment volumes, ipsilateral lung, aorta, and heart are determined and compared to those determined using the TG-43 approach. Considerable variation with source energy and differences between model-based and TG-43 doses are found for both treatment volumes and organs. Doses to the heart and aorta generally increase with increasing source energy. TG-43 underestimates the dose to the heart and aorta for all implants except those nearest to these organs where the dose is overestimated. Results suggest that model-based dose calculations are crucial for selecting prescription doses, comparing clinical endpoints, and studying radiobiological effects for permanent implant lung brachytherapy.

Estimation of the displacement of cardiac substructures and the motion of the coronary arteries using electrocardiographic gating

Purpose

The aim of this study was to quantify the displacement of cardiac substructures, including the anterior myocardial territory (AMT), left ventricle, and coronary arteries during a normal cardiac cycle.

Materials and methods

Computed tomography (CT) images with retrospective electrocardiographic gating of 17 eligible patients were obtained. All images were reconstructed automatically for the end-diastolic and end-systolic phases. CT scanning without contrast at a random phase and a selected vertebral body were used as references to measure three-dimensionaldisplacements of the cardiac substructures.

Results

The displacement between the end-diastolic and end-systolic phases (D_d-s) was greater than that between the end-systolic and random phases and between the end-diastolic and random cardiac phases. The largest displacements for the heart were in the left, posterior, and inferior directions with an average D_d-s of approximately 4–6 mm. The average D_d-s for the AMT and left ventricle was 1.2–2.7 mm in the anterior and right directions, 4.3–7.8 mm in left and posterior directions, and 4.9–6.3 mm in superior and inferior directions. For the coronary arteries, the average D_d-s was 2.8–5.9 mm in the anterior-posterior direction, 3.5–6.6 mm in left-right direction, and 3.8–5.3 mm in the superior-inferior direction. Inter-observer agreement was excellent for the heart, AMT, and left ventricle (kappa coefficient, >0.75 for all) and good for most coronary arteries in three dimensions (kappa coefficient, 0.511–0.687). The D_d-s did not differ significantly between men and women.

Conclusion

Most average displacements of the cardiac substructures and coronary arteries were 3–8 mm in three dimensions. These findings will be useful to accurately estimate the radiation dose to cardiac substructures during thoracic radiation and to evaluate the risk of radiation-related heart disease.

Follow-up study of abnormal biological indicators and gene expression in the peripheral blood of three accidentally exposed persons

In order to identify biomarkers for early diagnosis and/or for therapeutic targets in the delayed health effects of ionizing radiation, we analyzed the subgroups of lymphocytes, serum protein levels and gene expression profiles in the peripheral blood of three ⁶⁰Co γ-ray accidentally exposed persons during the three years after irradiation. Flow cytometry analyses and agarose gel electrophoresis were applied to investigate the subgroups of lymphocytes and the composition of serum proteins, respectively. Gene expression profiling was obtained using a whole genome gene expression chip assay. Both the percentage of CD4+ T lymphocytes and the ratio of Th to Ts were reduced compared with the normal control values. The percentage of albumin decreased whereas beta globulin increased. There were 285 up-regulated and 446 down-regulated genes in irradiated samples relative to the control samples. The expression of KDR, CEACAM8 and OSM was validated by RT-PCR. The majority of the differentially expressed genes encode proteins associated with the immune response, inflammation, oncogenesis, cell structure, oxidative stress, neuro-hormone regulation, reproduction, susceptibility to psychiatric disorders, or transcriptional regulation. We have identified a number of promising novel candidates that have potential for serving as biomarkers for delayed damage. Furthermore, the changes in the immunological indicator CD4+ T cells, and the ratio of CD4+ T to CD8+ T cells may be biomarkers for the prediction of delayed damage by ionizing radiation. The findings of our study are useful for forming a comprehensive understanding of the mechanisms underlying the delayed effects of ionizing radiation.

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.

Cardiac injury after 10 gy total body irradiation: indirect role of effects on abdominal organs

The objective of this study was to determine whether radiation-induced injury to the heart after 10 Gy total body irradiation (TBI) is direct or indirect. Young male WAG/RijCmcr rats received a 10 Gy single dose using TBI, upper hemi-body (UHB) irradiation, lower hemi-body (LHB) irradiation, TBI with the kidneys shielded or LHB irradiation with the intestines shielded. Age-matched, sham-irradiated rats served as controls. The lipid profile, kidney injury, heart and liver morphology and cardiac function were determined up to 120 days after irradiation. LHB, but not UHB irradiation, increased the risk factors for cardiac disease as well as the occurrence of cardiac and kidney injury in a way that was quantitatively and qualitatively similar to that observed after TBI. Shielding of the kidneys prevented the increases in risk factors for cardiac disease. Shielding of the intestines did not prevent the increases in risk factors for cardiac disease. There was no histological evidence of liver injury 120 days after irradiation. Injury to the heart from irradiation appears to be indirect, supporting the notion that injury to abdominal organs, principally the kidneys, is responsible for the increased risk factors for and the occurrence of cardiac disease after TBI and LHB irradiation.

Persistence of apoptosis and inflammatory responses in the heart and bone marrow of mice following whole-body exposure to ²⁸Silicon (²⁸Si) ions

It has been well established that the bone marrow (BM) is a radiosensitive tissue, but the radiosensitivity of the heart is poorly understood. In this study, we investigated the comparative effects of ²⁸Silicon (²⁸Si) ions (one type of heavy ion found in space) on tissue from the heart and the BM of exposed mice. We gave adult male CBA/CaJ mice a whole-body exposure to a total dose of 0, 0.1, 0.25, or 0.5 Gy of 300 MeV/nucleon (n) ²⁸Si ions, using a fractionated schedule (two exposures, 15 days apart that totaled each selected dose). The heart and BM were collected from 5 mice per treatment group at various times up to 6 months post-irradiation. In each mouse, we obtained tissue lysates from the heart and from the total population of BM cells for measuring the levels of cleaved poly (ADP-ribose) polymerase (cleaved PARP, a marker of apoptotic cell death) and the levels of activated nuclear factor-kappa B (NF-κB) and selected NF-κB-regulated cytokines known to be involved in inflammatory responses. Our data showed that, up to 6 months post-irradiation, the levels of apoptotic cell death and inflammatory responses in tissues from the heart and BM collected from exposed mice were statistically higher than those in sham controls. Hence, these findings are suggestive of chronic apoptotic cell death and inflammation in both tissues after exposure to ²⁸Si ions. In summary, our data are indicative of a possible association between exposure to ²⁸Si ions during space flight and long-term health risk.

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.

Cardiac complications after radical radiotherapy

Improvements in cancer therapy have led to increasing numbers of cancer survivors, and the long-term complications of these treatments are now becoming apparent. This article presents the current knowledge of adverse cardiovascular effects of radiotherapy to the chest. Medline literature searches relating to the cardiac complications of radiotherapy and subsequent prognosis were conducted. Potential adverse effects of mediastinal irradiation are numerous and can include coronary artery disease, pericarditis, cardiomyopathy, and valvular disease. Damage seems to be related to radiation dose, volume of irradiated heart, age at exposure, technique of chest irradiation, and patient-specific factors. The advent of technology and the newer sophisticated techniques in treatment planning and delivery are expected to decrease the incidence of cardiovascular diseases after radiation of the mediastinal structures. In any case, patients subjected to irradiation of the mediastinal structures require close multidisciplinary clinical monitoring.

Cardiovascular complications of radiation therapy for thoracic malignancies: the role for non-invasive imaging for detection of cardiovascular disease

Radiation exposure to the thorax is associated with substantial risk for the subsequent development of cardiovascular disease. Thus, the increasing role of radiation therapy in the contemporary treatment of cancer, combined with improving survival rates of patients undergoing this therapy, contributes to a growing population at risk of cardiovascular morbidity and mortality. Associated cardiovascular injuries include pericardial disease, coronary artery disease, valvular disease, conduction disease, cardiomyopathy, and medium and large vessel vasculopathy-any of which can occur at varying intervals following irradiation. Higher radiation doses, younger age at the time of irradiation, longer intervals from the time of radiation, and coexisting cardiovascular risk factors all predispose to these injuries. The true incidence of radiation-related cardiovascular disease remains uncertain due to lack of large multicentre studies with a sufficient duration of cardiovascular follow-up. There are currently no consensus guidelines available to inform the optimal approach to cardiovascular surveillance of recipients of thoracic radiation. Therefore, we review the cardiovascular consequences of radiation therapy and focus on the potential role of non-invasive cardiovascular imaging in the assessment and management of radiation-related cardiovascular disease. In doing so, we highlight characteristics that can be used to identify individuals at risk for developing post-radiation cardiovascular disease and propose an imaging-based algorithm for their clinical surveillance.

SNP in TXNRD2 associated with radiation-induced fibrosis: a study of genetic variation in reactive oxygen species metabolism and signaling

PURPOSE

The aim of the study was to identify noninvasive markers of treatment-induced side effects. Reactive oxygen species (ROS) are generated after irradiation, and genetic variation in genes related to ROS metabolism might influence the level of radiation-induced adverse effects (AEs).

METHODS AND MATERIALS

92 breast cancer (BC) survivors previously treated with hypofractionated radiation therapy were assessed for the AEs subcutaneous atrophy and fibrosis, costal fractures, lung fibrosis, pleural thickening, and telangiectasias (median follow-up time 17.1 years). Single-nucleotide polymorphisms (SNPs) in 203 genes were analyzed for association to AE grade. SNPs associated with subcutaneous fibrosis were validated in an independent BC survivor material (n=283). The influence of the studied genetic variation on messenger ribonucleic acid (mRNA) expression level of 18 genes previously associated with fibrosis was assessed in fibroblast cell lines from BC patients.

RESULTS

Subcutaneous fibrosis and atrophy had the highest correlation (r=0.76) of all assessed AEs. The nonsynonymous SNP rs1139793 in TXNRD2 was associated with grade of subcutaneous fibrosis, the reference T-allele being more prevalent in the group experiencing severe levels of fibrosis. This was confirmed in another sample cohort of 283 BC survivors, and rs1139793 was found significantly associated with mRNA expression level of TXNRD2 in blood. Genetic variation in 24 ROS-related genes, including EGFR, CENPE, APEX1, and GSTP1, was associated with mRNA expression of 14 genes previously linked to fibrosis (P≤.005).

CONCLUSION

Development of subcutaneous fibrosis can be associated with genetic variation in the mitochondrial enzyme TXNRD2, critically involved in removal of ROS, and maintenance of the intracellular redox balance.

Cardiac complications of thoracic irradiation

Adjuvant radiation therapy in the management of early stage breast cancer, Hodgkin's disease, and to a lesser extent other thoracic malignancies has led to a significant improvement in disease-specific survival. Cardiovascular disease is now the most common nonmalignancy cause of death in radiation-treated cancer survivors, most often occurring decades after treatment. The spectrum of radiation-induced cardiac disease is broad, potentially involving any component of the heart. The relative risk of coronary artery disease, congestive heart failure, valvular heart disease, pericardial disease, conduction abnormalities, and sudden cardiac death is particularly increased. Over the years contemporary techniques have been introduced to reduce cardiac morbidity and mortality in radiation-treated cancer survivors; however, the long-term effects on the heart still remain unclear, mandating longer follow-up. Awareness and early identification of potential cardiac complications is crucial in cancer survivors, with the management often being quite complex. This review examines the epidemiology of radiation-induced cardiac disease together with its pathophysiology and explores the available treatment strategies and the potential utility of various screening strategies for affected cancer survivors.

The influence of adjuvant therapy on cardiorespiratory fitness in early-stage breast cancer seven years after diagnosis: the Cooper Center Longitudinal Study

We examined cardiorespiratory fitness (CRF) levels in early stage breast cancer patients and determined whether CRF differs as a function of adjuvant therapy regimen. A total of 180 early breast cancer patients representing three treatment groups (surgery only, single-, and multi-modality adjuvant therapy) in the Cooper Center Longitudinal Study (CCLS) were studied. A non-cancer control group (n = 180) matched by sex, age, and date of the CCLS visit was included. All subjects underwent an incremental exercise tolerance test to symptom limitation to assess CRF (i.e., peak metabolic equivalents [METs] and time to exhaustion). The mean time from breast cancer diagnosis to exercise tolerance testing was 7.4 ± 6.2 years. In adjusted analyses, time to exhaustion and peak METs were incrementally impaired with the addition of surgery, single-, and multi-modality adjuvant therapy compared to those of matched controls (p = 0.006 and 0.028, respectively). CRF was lowest in the multi-modality group compared to all other groups (all p's < 0.05). Despite being 7 years post-diagnosis, asymptomatic early breast cancer survivors have marked reductions in CRF. Patients treated with multi-modal adjuvant therapy have the greatest impairment in CRF.

Caspase-3 activation and increased procollagen type I in irradiated hearts

The caspase-3-cleaved presence was evaluated in this study in the heart of irradiated rats, during the decline of ventricular function. Female Wistar rats were irradiated with a single dose of radiation (15 Gy) delivered directly to the heart and the molecular, histological and physiological evaluations were performed at thirteen months post-irradiation. The expressions of procollagen type I, TGF-ß1 and caspase-3-cleaved were analyzed using Western blotting. Cardiac structural and functional alterations were investigated by echocardiography and electron microscopy. In the irradiated group, the levels of procollagen type I, TGF-ß1 and caspase-3-cleaved are increased. Significant histological changes (degeneration of heart tissue and collagen deposition) and functional (reduced ejection fraction) were observed. Data suggest that the cardiac function decline after exposure to ionizing radiation is related, in part, to increased collagen and increased caspase-3-cleaved.

Enhanced sensitivity to low dose irradiation of ApoE-/- mice mediated by early pro-inflammatory profile and delayed activation of the TGFβ1 cascade involved in fibrogenesis

Aim

Investigating long-term cardiac effects of low doses of ionizing radiation is highly relevant in the context of interventional cardiology and radiotherapy. Epidemiological data report that low doses of irradiation to the heart can result in significant increase in the cardiovascular mortality by yet unknown mechanisms. In addition co-morbidity factor such as hypertension or/and atherosclerosis can enhance cardiac complications. Therefore, we explored the mechanisms that lead to long-term cardiac remodelling and investigated the interaction of radiation-induced damage to heart and cardiovascular systems with atherosclerosis, using wild-type and ApoE-deficient mice.

Methods and Results

ApoE−/− and wild-type mice were locally irradiated to the heart at 0, 0.2 and 2 Gy (RX). Twenty, 40 and 60 weeks post-irradiation, echocardiography were performed and hearts were collected for cardiomyocyte isolation, histopathological analysis, study of inflammatory infiltration and fibrosis deposition. Common and strain-specific pathogenic pathways were found. Significant alteration of left ventricular function (eccentric hypertrophy) occurred in both strains of mice. Low dose irradiation (0.2 Gy) induced premature death in ApoE−/− mice (47% died at 20 weeks). Acute inflammatory infiltrate was observed in scarring areas with accumulation of M1-macrophages and secretion of IL-6. Increased expression of the fibrogenic factors (TGF-β1 and PAI-1) was measured earlier in cardiomyocytes isolated from ApoE−/− than in wt animals.

Conclusion

The present study shows that cardiac exposure to low dose of ionizing radiation induce significant physiological, histopathological, cellular and molecular alterations in irradiated heart with mild functional impairment. Atherosclerotic predisposition precipitated cardiac damage induced by low doses with an early pro-inflammatory polarization of macrophages.

Breast radiotherapy: less is more?

A 3 week schedule of whole breast radiotherapy is firmly established in the UK and is becoming more accepted internationally, especially as accelerated partial breast radiotherapy regimens become more common. It seems that a 3 week schedule is unlikely to be the lower limit of whole breast hypofractionation and the partial breast may even be adequately treated with just a single treatment. It is, however, essential that these hypotheses are rigorously tested within well-designed trials to ensure the highest quality of radiotherapy. This overview will address the rationale for hypofractionation in breast cancer, discuss past trials and outline the design of current studies.

Adjuvant radiotherapy in the management of axillary node negative invasive breast cancer: a qualitative systematic review

PURPOSE

To actualize and to detail guidelines used in technical radiotherapy and indications for innovative radiation technologies in early axillary node negative breast cancer (BC).

METHODS

Dosimetric and treatment planning studies, phase II and III trials, systematic reviews and retrospective studies were all searched (Medline(®) database). Their quality and clinical relevance were also checked against validated checklists. A level of evidence was associated for each result.

RESULTS

A total of 75 references were included. Adjuvant BC radiotherapy (50Gy/25 fractions/5 weeks followed by a tumor boost of 16Gy/8 fractions) is still the standard of care. Overall treatment time could be shortened for patients who present with low local relapse risk BC by using either hypofractionated whole breast irradiation; or accelerated partial breast irradiation. BC IMRT is not used in current practice.

CONCLUSION

Our group aimed to provide guidelines for technical and clinical applications of innovative BC radiation technologies.

Radiation biology and radiation protection

For protection purposes, the biological effects of radiation are separated into stochastic effects (cancer, hereditary effects) presumed to be unicellular in origin, and tissue reactions due to injury in populations of cells. The latter are deterministic effects, renamed 'tissue reactions' in the 2007 Recommendations of the International Commission on Radiological Protection because of the increasing evidence of the ability to modify responses after irradiation. Tissue reactions become manifest either early or late after doses above a threshold dose, which is the basis for recommended dose limits for avoiding such effects. Latency time before manifestation is related to cell turnover rates, and tissue proliferative and structural organisation. Threshold doses have been defined for practical purposes at 1% incidence of an effect. In general, threshold doses are lower for longer follow-up times because of the slow progression of injury before manifestation. Radiosensitive individuals in the population may contribute to low threshold doses, and in the future, threshold doses may be increased by the use of various biological response modifiers post irradiation for reducing injury. Threshold doses would be expected to be higher for fractionated or protracted doses, unless doses below the threshold dose only cause single-hit-type events that are not modified by repair/recovery phenomena, or if different mechanisms of injury are involved at low and high doses.

Long-term epidemiological studies of atomic bomb survivors in Hiroshima and Nagasaki: study populations, dosimetry and summary of health effects

The Radiation Effects Research Foundation succeeded 28 years' worth of activities of the Atomic Bomb Casualty Commission on long-term epidemiological studies in Hiroshima and Nagasaki. It has three major cohorts of atomic bomb survivors, i.e. the Life Span Study (LSS) of 120,000 people, the In Utero Cohort of 3600 and the Second Generation Study (F(1)) of 77,000. The LSS and F(1) studies include a periodic health examination for each sub-cohort, i.e. the Adult Health Study and the F(1) Clinical Study, respectively. An extensive individual dose estimation was conducted and the system was published as the Dosimetry System established in 2002 (DS02). As results of these studies, increases of cancers in relation to dose were clearly shown. Increases of other mortality causes were also observed, including heart and respiratory diseases. There has been no evidence of genetic effects in the survivors' children, including cancer and other multi-factorial diseases. The increase in the expected mortality number in the next 10 y would allow the analyses of further details of the observed effects related to atomic bomb exposures.