Pathology and biology of radiation-induced cardiac disease

Total extracts from Abelmoschus manihot (L.) alleviate radiation-induced cardiomyocyte ferroptosis via regulating redox imbalances mediated by the NOX4/xCT/GPX4 axis

ETHNOPHARMACOLOGICAL RELEVANCE

Radiation-induced heart disease (RIHD) is one of the most serious complications in patients receiving chest radiotherapy, partially offsetting its benefits. At present, there is a lack of effective treatments for RIHD. Ferroptosis is a newly discovered type of cell death that results from iron-dependent lipid peroxide accumulation. It was recently shown that irradiation generates severe ferroptosis, providing new insights for the treatment of RIHD. Abelmoschus manihot (L.) possesses excellent pharmacological properties and is widely used in treating various ischemic heart and brain diseases; however, its efficacy and mechanism in treating RIHD are unknown.

AIM

This study aimed to investigate the efficacy and mechanism of total extracts from A. manihot (L.) (TEA) in treating RIHD.

MATERIALS AND METHODS

C57BL/6 mice and H9C2 cells were exposed to irradiation to induce RIHD in vivo and in vitro, respectively. In vivo, we evaluated the protective effects of TEA (150 and 300 mg/kg) on RIHD. Body and heart weight changes of mice were calculated in each group, and malondialdehyde (MDA) level, glutathione/oxidized glutathione (GSH/GSSH) and nicotinamide adenine dinucleotide phosphate (NADPH/NADP+) ratios, western blot, heart histology, and immunohistochemistry were used to evaluate TEA effectiveness. We identified the potential mechanism of radiation-induced cardiomyocyte injury in H9C2 cells treated with small interfering RNA. We determined the effective dose of TEA (0.6 mg/mL) using a Cell Counting Kit-8 assay. Intracellular Fe2+ and lipid peroxidation levels were detected by Phen Green™ SK diacetate probe, BODIPY 581/591 C11 staining, and MDA, GSH, and NADPH kits, and the level of target protein was evaluated by immunofluorescence and western blot.

RESULTS

Radiation inhibited system Xc-cystine (xCT)/glutathione peroxidase 4 (GPX4) expression and activity in cardiomyocytes in a time and dose-dependent manner. After silencing xCT/GPX4, MDA significantly increased and GSH/GSSH and NADPH/NADP+ ratios were reduced. xCT/GPX4 inhibition drove ferroptosis in radiation-induced H9C2 injury. Oxidative stress in H9C2 was significantly enhanced by irradiation, which also significantly increased NADPH oxidase 4 (NOX4) expression and inhibited nuclear factor E2-related factor 2 (Nrf2) expression in vivo and in vitro. Inhibition of xCT/GPX4 drove ferroptosis in radiation-induced H9C2 injury, which was aggravated by inactivation of Nrf2 and alleviated by inhibition of NOX4. Compared with the ionizing radiation-only group, TEA improved body weight loss, MDA levels, and histological changes induced by irradiation in mice hearts, and increased the ratio of GSH/GSSH and NADPH/NADP+in vivo; it also reduced lipid peroxidation and intracellular Fe2+ accumulation, restored MDA levels, and elevated the ratios of GSH/GSSH and NADPH/NADP+ in irradiation-injured H9C2 cells. TEA up-regulated Nrf2, xCT, and GPX4 expression and inhibited NOX4 expression in vivo and in vitro.

CONCLUSIONS

Ferroptosis induced by redox imbalance mediated through the NOX4/xCT/GPX4 axis is a potential mechanism behind radiation-induced cardiomyocyte injury, and can be prevented by TEA.

Computational modelling of cardiovascular pathophysiology to risk stratify commercial spaceflight

For more than 60 years, humans have travelled into space. Until now, the majority of astronauts have been professional, government agency astronauts selected, in part, for their superlative physical fitness and the absence of disease. Commercial spaceflight is now becoming accessible to members of the public, many of whom would previously have been excluded owing to unsatisfactory fitness or the presence of cardiorespiratory diseases. While data exist on the effects of gravitational and acceleration (G) forces on human physiology, data on the effects of the aerospace environment in unselected members of the public, and particularly in those with clinically significant pathology, are limited. Although short in duration, these high acceleration forces can potentially either impair the experience or, more seriously, pose a risk to health in some individuals. Rather than expose individuals with existing pathology to G forces to collect data, computational modelling might be useful to predict the nature and severity of cardiovascular diseases that are of sufficient risk to restrict access, require modification, or suggest further investigation or training before flight. In this Review, we explore state-of-the-art, zero-dimensional, compartmentalized models of human cardiovascular pathophysiology that can be used to simulate the effects of acceleration forces, homeostatic regulation and ventilation-perfusion matching, using data generated by long-arm centrifuge facilities of the US National Aeronautics and Space Administration and the European Space Agency to risk stratify individuals and help to improve safety in commercial suborbital spaceflight.

Understanding cardiac events in breast cancer (UCARE): pilot cardio-oncology assessment and surveillance pathway for breast cancer patients

PURPOSE

In Ireland, over 3000 patients are diagnosed with breast cancer annually, and 1 in 9 Irish women will be diagnosed with breast cancer in their lifetime. There is evidence that female breast cancer survivors are more likely to die of cardiovascular disease than their age-matched counterparts. Specific services for cancer patients suffering from cancer therapy related cardiovascular toxicity have led to a higher incidence of safe anti-cancer treatment completion. Such services are not widely available in our jurisdiction, and the purpose of this trial is to remedy this situation.

METHODS

This protocol describes a prospective, single arm, pilot feasibility study implementing a dedicated Cardio-Oncology assessment and surveillance pathway for patients receiving multimodal breast cancer treatment. It incorporates novel biomarker and radiomic surveillance and monitoring approaches for cancer-therapy related cardiac dysfunction into routine care for breast cancer patients undergoing adjuvant systemic chemotherapy.

RESULTS

Declaration of results will via peer reviewed academic journals, and communicated directly to key knowledge users both nationally and internationally. This engagement will be critical to enable to healthcare services and policy sector make informed decisions or valuable changes to clinical practice, expenditure and/or systems development to support specialized Cardio-Oncology clinical pathways. All data is to be made available upon request.

CONCLUSION

Dedicated cardio-oncology services have been recommended in recent literature to improve patient outcomes. Our protocol describes a feasibility study into the provision of such services for breast cancer.

The potential treatment of N-acetylcysteine as an antioxidant in the radiation-induced heart disease

Background

Radiation-induced heart disease (RIHD) is a serious complication of thoracic tumor radiotherapy that substantially affects the quality of life of cancer patients. Oxidative stress plays a pivotal role in the occurrence and progression of RIHD, which prompted our investigation of an innovative approach for treating RIHD using antioxidant therapy.

Methods

We used 8-week-old male Sprague-Dawley (SD) rats as experimental animals and H9C2 cells as experimental cells. N-acetylcysteine (NAC) was used as an antioxidant to treat H9C2 cells after X-ray irradiation in this study. In the present study, the extent of cardiomyocyte damage caused by X-ray exposure was determined, alterations in oxidation/antioxidation levels were assessed, and changes in the expression of genes related to mitochondria were examined. The degree of myocardial tissue and cell injury was also determined. Dihydroethidium (DHE) staining, reactive oxygen species (ROS) assays, and glutathione (GSH) and manganese superoxide dismutase (Mn-SOD) assays were used to assess cell oxidation/antioxidation. Flow cytometry was used to determine the mitochondrial membrane potential and mitochondrial permeability transition pore (mPTP) opening. High-throughput transcriptome sequencing and bioinformatics analysis were used to elucidate the expression of mitochondria-related genes in myocardial tissue induced by X-ray exposure. Polymerase chain reaction (PCR) was used to verify the expression of differentially expressed genes.

Results

X-ray irradiation damaged myocardial tissue and cells, resulting in an imbalance of oxidative and antioxidant substances and mitochondrial damage. NAC treatment increased cell counting kit-8 (CCK-8) levels (P=0.02) and decreased lactate dehydrogenase (LDH) release (P=0.02) in cardiomyocytes. It also reduced the level of ROS (P=0.002) and increased the levels of GSH (P=0.04) and Mn-SOD (P=0.01). The mitochondrial membrane potential was restored (P<0.001), and mPTP opening was inhibited (P<0.001). Transcriptome sequencing and subsequent validation analyses revealed a decrease in the expression of mitochondria-related genes in myocardial tissue induced by X-ray exposure, but antioxidant therapy did not reverse the related DNA damage.

Conclusions

Antioxidants mitigated radiation-induced myocardial damage to a certain degree, but these agents did not reverse the associated DNA damage. These findings provide a new direction for future investigations by our research group, including exploring the treatment of RIHD-related DNA damage.

EEPD1 attenuates radiation-induced cardiac hypertrophy and apoptosis by degrading FOXO3A in cardiomyocytes

Radiation-induced heart disease (RIHD) is a severe delayed complication of thoracic irradiation (IR). Endonuclease/exonuclease/phosphatase family domain-containing 1 ( EEPD1) plays an important role in DNA damage repair, but its role in RIHD is less known. In this study, EEPD1 global knockout mice, C57BL/6J mice, and C57BL/6J mice overexpressing EEPD1 are treated with radiation at a total dose of 20 Gy or 0 Gy. After 9 weeks, echocardiography is used to assess cardiac hypertrophy and apoptosis. The results show that EEPD1 deletion exacerbates radiation-induced cardiac hypertrophy and apoptosis, while EEPD1 overexpression has the opposite effect. Further mechanistic investigations reveal that EEPD1 interacts with FOXO3A and destabilizes it by catalyzing its deubiquitination. Inhibition of FOXO3A ameliorates cardiac hypertrophy and apoptosis after EEPD1 knockdown. Thus, EEPD1 protects against radiation-induced cardiac hypertrophy and apoptosis via destabilization of FOXO3A, which may offer new insight into therapeutic strategies for RIHD.

Dexmedetomidine ameliorates x-ray-induced myocardial injury via alleviating cardiomyocyte apoptosis and autophagy

BACKGROUND

Radiotherapy is a primary local treatment for tumors, yet it may lead to complications such as radiation-induced heart disease (RIHD). Currently, there is no standardized approach for preventing RIHD. Dexmedetomidine (Dex) is reported to have cardio-protection effects, while its role in radiation-induced myocardial injury is unknown. In the current study, we aimed to evaluate the radioprotective effect of dexmedetomidine in X-ray radiation-treated mice.

METHODS

18 male mice were randomized into 3 groups: control, 16 Gy, and 16 Gy + Dex. The 16 Gy group received a single dose of 16 Gy X-ray radiation. The 16 Gy + Dex group was pretreated with dexmedetomidine (30 µg/kg, intraperitoneal injection) 30 min before X-ray radiation. The control group was treated with saline and did not receive X-ray radiation. Myocardial tissues were collected 16 weeks after X-ray radiation. Hematoxylin-eosin staining was performed for histopathological examination. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining was performed to assess the state of apoptotic cells. Immunohistochemistry staining was performed to examine the expression of CD34 molecule and von Willebrand factor. Besides, western blot assay was employed for the detection of apoptosis-related proteins (BCL2 apoptosis regulator and BCL2-associated X) as well as autophagy-related proteins (microtubule-associated protein 1 light chain 3, beclin 1, and sequestosome 1).

RESULTS

The findings demonstrated that 16 Gy X-ray radiation resulted in significant changes in myocardial tissues, increased myocardial apoptosis, and activated autophagy. Pretreatment with dexmedetomidine significantly protects mice against 16 Gy X-ray radiation-induced myocardial injury by inhibiting apoptosis and autophagy.

CONCLUSION

In summary, our study confirmed the radioprotective effect of dexmedetomidine in mitigating cardiomyocyte apoptosis and autophagy induced by 16 Gy X-ray radiation.

Approach to Lymphoma-Associated Cardiomyopathy

Cardiomyopathy is a disease of the myocardium that affects the heart structure and function, eventually resulting in heart failure, valvular regurgitation, arrhythmia, or even sudden cardiac death. Occurring following treatment of lymphoma, both Hodgkin's and Non-Hodgkin's, cardiomyopathy is a feared complication in these cancer survivors due to its significant association with morbidity and mortality. A review of the literature was conducted using a combination of keywords including "Cardiomyopathy," "Anthracycline," "Radiation," "Pathogenesis," and "Management." Anthracyclines and radiation are prominent entities explored in the discussion of lymphoma-associated cardiomyopathy, whereby the formation of reactive oxygen species following treatment with both has been seen in the pathogenesis. The current standard of care thus far for anthracycline-induced cardiomyopathy includes heart failure medications such as beta-blockers, angiotensin-converting enzyme inhibitors, aldosterone receptor antagonists, and loop-diuretics. On the other hand, radiation-induced cardiomyopathy management has not been well-established yet in literature, with agents such as antioxidants and anti-inflammatory drugs still being studied in rat models. The treatment approach to cardiotoxicity in a lymphoma patient should consist of a collaboration between the oncologist and cardiologist prior to lymphoma treatment initiation, to stratify the risk of development of cardiomyopathy in the patient, and decide the best chemotherapy or radiotherapy agent, dosing, and surveillance technique.

Inhibitor of Wnt receptor 1 suppresses the effects of Wnt1, Wnt3a and β‑catenin on the proliferation and migration of C6 GSCs induced by low‑dose radiation

The radioresistance of glioma is an important cause of treatment failure and tumor aggressiveness. In the present study, under performed with linear accelerator, the effects of 0.3 and 3.0 Gy low‑dose radiation (LDR) on the proliferation and migration of C6 glioma stem cells in vitro were examined by flow cytometric analysis, immunocytochemistry and western blot analysis. It was found that low‑dose ionizing radiation (0.3 Gy) stimulated the proliferation and migration of these cells, while 3.0 Gy ionizing radiation inhibited the proliferation of C6 glioma stem cells, which was mediated through enhanced Wnt/β‑catenin signaling, which is associated with glioma tumor aggressiveness. LDR treatment increased the expression of the DNA damage marker γ‑H2AX but promoted cell survival with a significant reduction in apoptotic and necrotic cells. When LDR cells were also treated with an inhibitor of Wnt receptor 1 (IWR1), cell proliferation and migration were significantly reduced. IWR1 treatment significantly inhibited Wnt1, Wnt3a and β‑catenin protein expression. Collectively, the current results demonstrated that IWR1 treatment effectively radio‑sensitizes glioma stem cells and helps to overcome the survival advantages promoted by LDR, which has significant implications for targeted treatment in radioresistant gliomas.

Levocabastine ameliorates cyclophosphamide-induced cardiotoxicity in Swiss albino mice: Targeting TLR4/NF-κB/NLRP3 signaling pathway

Cyclophosphamide (CP), although a potent anti-cancer drug, causes cardiotoxicity as a side effect that limits its use. Hence, a specific medicine that can lower cardiotoxicity and be utilised as an adjuvant in cancer treatment is very much needed. In this light, we intended to assess the protective potential of levocabastine (LEV) on CP-induced cardiotoxicity in Swiss albino mice. Mice were administered LEV (50 and 100 μg/kg, i.p.) daily for 14 days and CP at 200 mg/kg, intraperitoneally once on the 7th day. On the 15th day, mice were weighed, blood withdrawn then sacrificed and hearts were removed to estimate various biochemical and histopathological parameters. CP 200 mg/kg significantly increased cardiac troponin T, LDH, CK-MB, interleukin-1β, IL-6, TNF-α, TBARS, nitrite, and decreased CAT, GSH, and SOD levels, thus, manifested cardiac damage, inflammation, oxidative stress, and nitrative stress, cumulatively causing cardiotoxicity. CP also elevated the expression of various markers including cleaved caspase-3, NF-κB, TLR4, NLRP3, and fibrotic lesions in cardiac tissues, whereas decreased hematological parameters (RBCs, platelets, and Hb) to confirm cardiotoxicity. LEV and fenofibrate (FF) treatment reversed these changes towards normal and showed a significant protective effect against CP. The results showed the protective role of LEV in restoring CP-induced cardiotoxicity in terms of inflammation, apoptosis, oxidative stress, cardiac injury and histopathological damage. Thus, levocabastine can be used as an adjuvant to cyclophosphamide in cancer treatment but a thorough study with various animal cancer models is further needed to establish the fact.

Proton Beam Therapy for Breast Cancer

Given the radiobiological and physical properties of the proton, proton beam therapy has the potential to be advantageous for many patients compared with conventional radiotherapy by limiting toxicity and improving patient outcomes in specific breast cancer scenarios.

Efficacy of low-dose lung radiotherapy in the management of COVID-19 patients: a randomised, open-label study

OBJECTIVE

Evaluate role of low-dose radiotherapy (LDRT) in COVID-19 pneumonia.

METHODS

Sixty-five patients 40 years or older tested positive for COVID-19 reverse transcriptase-polymerase chain reaction with mild to moderate acute respiratory distress syndrome (ARDS), were randomised 1:1, from 4 June 2021, to either best standard of care (control arm) according to the Indian Council of Medical Research guidelines or a single dose of LDRT (LDRT-0.5Gy) to both lungs along with best standard of care (experimental arm). The primary outcome was either progression to severe disease (PaO2/FiO2 ratio <100 mmHg) within 28 days of randomisation or all-cause mortality at 28 days. If the primary outcome could have been prevented, it was considered "favourable"; if not, it was considered "unfavourable."

RESULTS

Thirty-three patients were allocated to experimental arm, 32 to control arm. An intention to treat analysis was performed. Unfavourable outcome was seen in 5 (15.2%) patients in experimental arm, vs , 12 (37.5%) patients in control arm, odds of an unfavourable outcome in experimental arm were 0.3, 95% CI 0.09-0.97; two-sided p = 0.04. Four and five patients died in experimental and control arm, respectively. No radiation-induced toxicity was observed.

CONCLUSION

LDRT reduced the number of patients with unfavourable outcome at 28 days.

ADVANCES IN KNOWLEDGE

One of the few randomised studies showing reduced unfavourable outcome in mild to moderate ARDS COVID-19 patients receiving LDRT.CTRI/2021/06/034001, Clinical Trials Registry - India (ICMR-NIMS).

Exposure to low-dose radiation in occupational settings and ischaemic heart disease: a systematic review and meta-analysis

Ionising radiation is a human carcinogen, but the evidence is less clear that exposure to low-dose ionising radiation (LDIR) increases the risk of adverse cardiovascular outcomes. We synthesised the literature of chronic occupational exposure to LDIR and cardiovascular disease, particularly for ischaemic heart disease (IHD).The literature search was conducted using three databases including studies published between 1990 and 2022. A quality assessment of the studies was completed using the Office of Health and Assessment and Translation Risk of Bias Rating Tool. We conducted meta-analyses for IHD mortality using random effects models using measures of excess relative risk per sievert (ERR/Sv) obtained from internal cohort comparisons, as well as with standardised mortality ratios (SMRs) from external cohort comparisons.We identified 2189 articles, and of these, 26 provided data on IHD and were retained. Most studies were classified as having a 'moderate' level of risk of bias. Fourteen and 10 studies reporting external radiation doses were included in meta-analyses using SMR and ERR/Sv, respectively. The meta-summary SMR was 0.81 (95% CI 0.74 to 0.89) with evidence of reduced risk but high heterogeneity across studies. For internal cohort measures, the summary ERR/Sv for a lagged exposure of 10 years was 0.10 (95% CI 0.01 to 0.20) with low heterogeneity. The subgroup analysis by lagged exposure time showed the strongest association were for the 15 and 20 years lag.Our findings suggest that occupational exposure to LDIR increases the risk IHD mortality and highlight the relevance of internal cohort comparisons.

Multimodal Imaging of Cancer Therapy-Related Cardiac Dysfunction in Breast Cancer-A State-of-the-Art Review

BACKGROUND

This review focuses on multimodality imaging of cardiotoxicity in cancer patients, with the aim of evaluating the effectiveness of different techniques in detecting and monitoring cardiac changes associated with cancer therapy.

METHODS

Eight studies were included in the review, covering various imaging modalities such as cardiac magnetic resonance imaging, echocardiography, and multigated acquisition scanning.

RESULTS

Cardiac magnetic resonance imaging emerged as the most definitive modality, offering real-time detection, comprehensive assessment of cardiac function, the ability to detect early myocardial changes, and superior detection of cardiotoxicity when compared to the other imaging modalities. The studies also emphasize the importance of parameters such as left ventricular ejection fraction and global longitudinal strain in assessing cardiac function and predicting cardiotoxicity.

CONCLUSION

Due to the common use of HER2 agents and anthracyclines within the breast cancer population, the LVEF as a critical prognostic measurement for assessing heart health and estimating the severity of left-sided cardiac malfunction is a commonly used endpoint. CTRCD rates differed between imaging modalities, with cardiac MRI the most sensitive. The use of multimodal cardiac imaging remains a nuanced area, influenced by local availability, the clinical question at hand, body habits, and medical comorbidities. All of the imaging modalities listed have a role to play in current care; however, focus should be given to increasing the provision of cardiac MRI for breast cancer patients in the future to optimize the detection of CTRCD and patient outcomes thereafter.

Cardiotoxicity in breast cancer treatment: Causes and mitigation

Survivorship issues and treatment related toxicities have considerably increased in breast cancer patients following improved therapeutic options. Cardiotoxicity has been a major treatment related side effects in these patients. Despite this being a well-known entity, the real magnitude of the problem remains an enigma. The amount of research in mitigation of cardiotoxicity or its management in breast cancer survivors is limited and there is an urgent need for finding solutions for the problem. In this article, we are reviewing the agents that cause cardiotoxicity and suggesting a proposal for follow up of breast cancer survivors in an attempt to reduce the magnitude of impact on their quality of life.

Uncommon short- and long-term cardiological side effects of thoracic radiation: a report of two cases

Radiotherapy is an essential treatment of more than 50% of oncohematological patients. Pericardial disorders and valvular heart disease are two common radiotherapy complications. Acute pericarditis is infrequent and usually underdiagnosed. Therefore, diagnostic suspicion and early treatment are mandatory to avoid the evolution to constrictive pericarditis. The prevalence of radiation-induced valvular heart disease is common in patients with a history of Hodgkin's lymphoma and breast cancer. It has distinctive characteristics from other etiologies and, thus, different therapeutic approaches. We present two cases of unusual complications of radiotherapy; the first one in the acute setting and the second one during the follow-up in the chronic phase. A multidisciplinary and individualized approach with specific considerations is decisive in the management of these patients.

Novel VEGFR2 inhibitors with thiazoloquinoxaline scaffold targeting hepatocellular carcinoma with lower cardiotoxic impact

Hepatocellular carcinoma (HCC) is a fatal tumor which is usually diagnosed at advanced stage. Molecular targeted drugs were used recently to treat HCC, however, due to serious side effects, mainly cardiotoxicity and emergence of resistance, there is demanding to explore new chemotherapeutics. 10 novel thiazoloquinoxaline derivatives coupled with different sulfonamide moieties 4(a-j) were designed and synthesized fulfilling pharmacophoric features of VEGFR-2 inhibition. Structures of all new compounds were verified via spectral and microanalytical data. After carrying in-vitro VEGFR-2 assay for compounds 4(a-j); sulfapyridine and sulfamethoxazole derivatives 4d and 4f showed potential inhibitory effect [61.04 and 83.35 nM], respectively, comparable to standard sorafenib [51.41 nM]. Both were then further evaluated for their cytocidal activity against HepG2 cell-line and against myocardium cells using H9C2 cell-line. As a result, only sulfapyridine derivative 4d exhibited a significant inhibition of HepG2 cells viability [IC50 = 4.31 μM]. Furthermore, it showed relatively lower cytotoxic impact against normal H9C2 myocardium cells [IC50, 33.47 μM] compared to that of sorafenib [IC50, 98.07 μM]. In-vivo study was carried out to determine myocardium safety of compound 4d on irradiated mice (8 Gy). In-vivo results of sulfapyridine derivative 4d showed normal cardiac enzyme function (CK) and serum catalase activity with significant reductions in LDH, cardiac TNF-α and caspase-9 levels, alongside with its efficacy in suppressing the expression of hepatic VEGF. In conclusion, sulfapyridine derivative 4d could be considered a promising candidate as VEGFR-2 inhibitor with less myocardium side effect.

Circulating cell-free methylated DNA reveals tissue-specific, cellular damage from radiation treatment

Radiation therapy is an effective cancer treatment, although damage to healthy tissues is common. Here we analyzed cell-free, methylated DNA released from dying cells into the circulation to evaluate radiation-induced cellular damage in different tissues. To map the circulating DNA fragments to human and mouse tissues, we established sequencing-based, cell-type-specific reference DNA methylation atlases. We found that cell-type-specific DNA blocks were mostly hypomethylated and located within signature genes of cellular identity. Cell-free DNA fragments were captured from serum samples by hybridization to CpG-rich DNA panels and mapped to the DNA methylation atlases. In a mouse model, thoracic radiation-induced tissue damage was reflected by dose-dependent increases in lung endothelial and cardiomyocyte methylated DNA in serum. The analysis of serum samples from patients with breast cancer undergoing radiation treatment revealed distinct dose-dependent and tissue-specific epithelial and endothelial responses to radiation across multiple organs. Strikingly, patients treated for right-sided breast cancers also showed increased hepatocyte and liver endothelial DNA in the circulation, indicating the impact on liver tissues. Thus, changes in cell-free methylated DNA can uncover cell-type-specific effects of radiation and provide a readout of the biologically effective radiation dose received by healthy tissues.

Late Effects of Chronic Low Dose Rate Total Body Irradiation on the Heart Proteome of ApoE-/- Mice Resemble Premature Cardiac Ageing

Recent epidemiologic studies support an association between chronic low-dose radiation exposure and the development of cardiovascular disease (CVD). The molecular mechanisms underlying the adverse effect of chronic low dose exposure are not fully understood. To address this issue, we have investigated changes in the heart proteome of ApoE deficient (ApoE^-/-) C57Bl/6 female mice chronically irradiated for 300 days at a very low dose rate (1 mGy/day) or at a low dose rate (20 mGy/day), resulting in cumulative whole-body doses of 0.3 Gy or 6.0 Gy, respectively. The heart proteomes were compared to those of age-matched sham-irradiated ApoE^-/- mice using label-free quantitative proteomics. Radiation-induced proteome changes were further validated using immunoblotting, enzyme activity assays, immunohistochemistry or targeted transcriptomics. The analyses showed persistent alterations in the cardiac proteome at both dose rates; however, the effect was more pronounced following higher dose rates. The altered proteins were involved in cardiac energy metabolism, ECM remodelling, oxidative stress, and ageing signalling pathways. The changes in PPARα, SIRT, AMPK, and mTOR signalling pathways were found at both dose rates and in a dose-dependent manner, whereas more changes in glycolysis and ECM remodelling were detected at the lower dose rate. These data provide strong evidence for the possible risk of cardiac injury following chronic low dose irradiation and show that several affected pathways following chronic irradiation overlap with those of ageing-associated heart pathology.

Deep inspiration breath hold: dosimetric benefits to decrease cardiac dose during postoperative radiation therapy for breast cancer patients

Background

Postoperative radiation therapy (RT) is the standard treatment for almost all patients diagnosed with breast cancer. Even with modern RT techniques, parts of the heart may still receive higher doses than those recommended by clinically validated dose limit restrictions, especially when the left breast is irradiated. Deep inspiration breath hold (DIBH) may reduce irradiated cardiac volume compared to free breathing (FB) treatment. This study aimed to evaluate the dosimetric impact on the heart and left anterior descending coronary artery (LAD) in FB and DIBH RT planning in patients with left breast cancer.

Materials and methods

A retrospective cohort study of women diagnosed with left-sided breast cancer submitted to breast surgery followed by postoperative RT from 2015 to 2019. All patients were planned with FB and DIBH and hypofractionated dose prescription (40.05 Gy in 15 fractions).

Results

68 patients were included in the study. For the coverage of the planned target volume evaluation [planning target volume (PTV) eval] there was no significant difference between the DIBH versus FB planning. For the heart and LAD parameters, all constraints evaluated favored DIBH planning, with statistical significance. Regarding the heart, median V16.8 Gy was 2.56% in FB vs. 0% in DIBH (p < 0.001); median V8.8 Gy was 3.47% in FB vs. 0% in DIBH (p < 0.001) and the median of mean heart dose was 1.97 Gy in FB vs. 0.92 Gy in DIBH (p < 0.001). For the LAD constraints D2% < 42 Gy, the median dose was 34.87 Gy in FB versus 5.8 Gy in DIBH (p < 0.001); V16.8 Gy < 10%, the median was 15.87% in FB versus 0% in DIBH (p < 0.001) and the median of mean LAD dose was 8.13Gy in FB versus 2.92Gy in DIBH (p < 0.001).

Conclusions

The DIBH technique has consistently demonstrated a significant dose reduction in the heart and LAD in all evaluated constraints, while keeping the same dose coverage in the PTV eval.

Cancer and Postradiotherapy Cardiotoxicity: How to Face Damage in Women’s Hearts?

Cancer and cardiovascular disease are the two main causes of death worldwide in both men and women. In the past decades, survival rate in cancer patients has substantially improved due to new treatments and developments in radiation therapy (RT). In women, breast cancer (BC) is the leading cause of cancer death and thoracic RT is a main component of the treatment in many cases. Nevertheless, despite new techniques that limit the area receiving RT, cardiac damage is still an important concern in BC patients. In this review, the following aspects will be addressed: pathophysiology of postradiotherapy heart damage in women with BC; mechanisms, diagnosis and prevention/management of heart damage; and future areas of potential research for radiotherapy injury in women.

Incidence risks for subtypes of heart diseases in a Russian cohort of Mayak Production Association nuclear workers

Heart diseases are one of the main causes of death. The incidence risks were assessed for various types of heart diseases (HDs) in a cohort of Russian nuclear workers of the Mayak Production Association (PA) who had been chronically occupationally exposed to external gamma and/ or internal alpha radiation. The study cohort included all workers (22,377 individuals) who had been hired at the Mayak PA during 1948-1982 and followed up until 31 December 2018. The mean gamma-absorbed dose to the liver (standard deviation) was 0.43 (0.63) Gy, and the mean alpha-absorbed dose to the liver was 0.25 (1.19) Gy. Excess relative risk (ERR) per unit liver-absorbed dose (Gy) was calculated based on maximum likelihood. At the end of the follow-up, 559 chronic rheumatic heart disease (CRHD), 7722 ischemic heart disease (IHD) [including 2185 acute myocardial infarction (AMI) and 3976 angina pectoris (AP)], 4939 heart failure (HF), and 3689 cardiac arrhythmia and conduction disorder (CACD) cases were verified in the study cohort. Linear model fits of the gamma dose response for HDs were best once adjustments for non-radiation factors (sex, attained age, calendar period, smoking status and alcohol consumption) and alpha dose were included. ERR/Gy in males and females was 0.17 (95% confidence intervals: 0.10, 0.26) and 0.23 (0.09, 0.38) for IHD; 0.18 (0.09, 0.29) and 0.26 (0.08, 0.49) for AP; - 0.01 (n/a, 0.1) and - 0.01 (n/a, 0.27) for AMI; 0.27 (0.16, 0.40) and 0.27 (0.10, 0.49) for HF; 0.32 (0.19, 0.46) and 0.05 (- 0.09, 0.22) for CACD; 0.73 (- 0.02, 2.40) and - 0.12 (- 0.50, 0.69) for CRHD, respectively. Sensitivity analyses demonstrated the persistence of a significant dose-response regardless of exclusion/inclusion of adjustments for known potential non-radiation confounders (smoking, alcohol consumption, body mass index, hypertension, diabetes mellitus), and it was only the magnitude of the risk estimate that varied. The risks of HD incidence were not modified with sex (except for the CACD risk). This study provides evidence for a significant association of certain types of HDs with cumulative dose of occupational chronic external exposure to gamma radiation.

Identification of circRNAs and circRNA-miRNA-mRNA regulatory network in radiation-induced heart disease

OBJECTIVE

Radiation-induced heart disease (RIHD) is one of the most common and serious long-term adverse effect after thoracic radiotherapy. Our aim was to investigate the potential molecular mechanism underlying RIHD using RNA-sequencing (RNA-seq) and bioinformatics methods.

MATERIALS AND METHODS

An RIHD rat model was established and transcription profiles were identified using RNA-seq. Differentially expressed circRNAs, miRNAs and mRNAs were identified. Enrichment of functions and signaling pathways analysis were performed based on GO and the KEGG database. Potential circRNA-miRNA-mRNA regulatory network underlying RIHD was established. qRT-PCR was used to validate the associated genes.

RESULTS

In total, 21 circRNAs, 26 miRNAs, and 178 mRNA transcripts were differentially expressed in RIHD. GO and KEGG pathway analyses identified that differentially expressed mRNAs were most enriched in pathways referring to endothelial function and vascular pathological processes. Nine circRNAs, 10 miRNAs, and 6 mRNA transcripts were most likely involved in vascular function and a candidate competitive endogenous RNA (ceRNA) network of circRNA-miRNA-mRNA was established, which were further validated by qRT-PCR.

CONCLUSIONS

Our study revealed that vascular pathology plays an important role in the early stage of RIHD. Furthermore, a circRNA-miRNA-mRNA ceRNA network was found that may be involved in the regulation of vascular function and RIHD.

Off-Target Effects of Cancer Therapy on Development of Therapy-Induced Arrhythmia: A Review

BACKGROUND

Advances in cancer therapeutics have improved overall survival and prognosis in this patient population; however, this has come at the expense of cardiotoxicity including arrhythmia.

SUMMARY

Cancer and its therapies are associated with cardiotoxicity via several mechanisms including inflammation, cardiomyopathy, and off-target effects. Among cancer therapies, anthracyclines and tyrosine kinase inhibitors (TKIs) are particularly known for their pro-arrhythmia effects. In addition to cardiomyopathy, anthracyclines may be pro-arrhythmogenic via reactive oxygen species (ROS) generation and altered calcium handling. TKIs may mediate their cardiotoxicity via inhibition of off-target tyrosine kinases. Ibrutinib-mediated inhibition of CSK may be responsible for the increased prevalence of atrial fibrillation. Further investigation is warranted to further elucidate the mechanisms behind arrhythmias in cancer therapies.

KEY MESSAGES

Arrhythmias are a common cardiotoxicity of cancer therapies. Cancer therapies may induce arrhythmias via off-target effects. Understanding the mechanisms underlying arrhythmogenesis associated with cancer therapies may help design cancer therapies that can avoid these toxicities.

Left atrial appendage volume as a prognostic Indicator of long-term mortality in Cancer survivors treated with thoracic radiation

BACKGROUND

Cancer survivors with prior chest radiation therapy (CXRT) frequently present with atrial fibrillation, heart failure, and have higher overall long-term mortality. There are no data examining the utility of left atrial (LA) and LA appendage (LAA) volume-indices to predict clinical outcomes in these patients.

OBJECTIVES

We examined the prognostic value of cardiac phase-dependent 3-D volume-rendered cardiac computerized tomography (CT)-derived LA and LAA volume-indices to predict mortality and major adverse cardiac events (MACE) in cancer survivors treated with thoracic irradiation.

METHOD

We screened 625 consecutive patients with severe aortic stenosis who had undergone transcatheter aortic valve replacement from 2012 to 2017. Based on the gated cardiac CT image quality, we included 184 patients (CXRT:43, non-CXRT:141) for further analysis. We utilized multiplane-3D-reconstructed cardiac CT images to calculate LA and LAA volume-indices, and examined the prognostic role of CCT-derived LA and LAA volume-indices in predicting the all-cause mortality, cardiovascular (CV) mortality, and MACE. We used multivariate cox-proportional hazard analysis to identify the clinical predictors of survival.

RESULTS

Overall, the CXRT group had significantly elevated LAA volume-index compared to non-CXRT group (CXRT:11.2 ± 8.9 ml/m²; non-CXRT:8.6 ± 4.5 ml/m², p = 0.03). On multivariate cox-proportional hazard analysis, the elevated LAA volume and LAA volume-index were the strongest predictors of reduced survival in CXRT group compared to non-CXRT group (LAA volume: RR = 1.03,95% CI 1.0-1.01, p = 0.01; and LAA volume index: RR = 1.05, 95% CI 1.0-1.01, p = 0.03). LAA volume > 21.9 ml was associated with increased mortality. In contrast, LA volume was not a significant predictor of mortality.

CONCLUSION

We describe a novel technique to assess LA and LAA volume using 3-D volume-rendered cardiac CT. This study shows enlarged LAA volume rather than LA volume carries a poor prognosis in cancer-survivors treated with prior CXRT. Compared to conventionally reported markers, LAA volume of > 21.9 ml was incremental to that of other risk factors.

Preclinical models of radiation-induced cardiac toxicity: Potential mechanisms and biomarkers

Radiation therapy (RT) is an important modality in cancer treatment with >50% of cancer patients undergoing RT for curative or palliative intent. In patients with breast, lung, and esophageal cancer, as well as mediastinal malignancies, incidental RT dose to heart or vascular structures has been linked to the development of Radiation-Induced Heart Disease (RIHD) which manifests as ischemic heart disease, cardiomyopathy, cardiac dysfunction, and heart failure. Despite the remarkable progress in the delivery of radiotherapy treatment, off-target cardiac toxicities are unavoidable. One of the best-studied pathological consequences of incidental exposure of the heart to RT is collagen deposition and fibrosis, leading to the development of radiation-induced myocardial fibrosis (RIMF). However, the pathogenesis of RIMF is still largely unknown. Moreover, there are no available clinical approaches to reverse RIMF once it occurs and it continues to impair the quality of life of long-term cancer survivors. Hence, there is an increasing need for more clinically relevant preclinical models to elucidate the molecular and cellular mechanisms involved in the development of RIMF. This review offers an insight into the existing preclinical models to study RIHD and the suggested mechanisms of RIMF, as well as available multi-modality treatments and outcomes. Moreover, we summarize the valuable detection methods of RIHD/RIMF, and the clinical use of sensitive radiographic and circulating biomarkers.

Experimental determination of breast skin dose using volumetric modulated arc therapy and field-in-field treatment techniques

Introduction:

The use of volumetric modulated arc therapy (VMAT) on the breast has several dosimetric advantages but its impact on skin dose should be evaluated and compared to well-established treatment techniques using tangential fields. The aim of this work is to contrast the skin dose for VMAT and field-in-field (FIF) and to estimate the magnitude of the skin dose involved.

Method:

The skin dose was measured, without build-up, using thermoluminescent dosimeter (TLD) and optically stimulated luminescence dosimeter (OSLD) in breast radiotherapy by an in-house anthropomorphic phantom. Two different treatment techniques were used: FIF and VMAT, based on the planning strategy proposed by Nicolini et al. The dose levels were 4300 cGy, 4600 cGy and 5600 cGy in 20 fractions. In vivo dosimetry with TLD for VMAT was performed for different breast sizes in the same locations as phantom measurements.

Results:

The ipsilateral phantom breast skin dose using both treatment techniques was equivalent. TLD measured doses by the VMAT technique were up to 5% higher than OSLD, although they agree if we consider the geometry uncertainty of the TLD. In accordance with in vivo dosimetry, the mean dose of the ipsilateral breast skin was 62 ± 6% (51%, 75%) relative to the prescribed dose, regardless of the breast size for the volumes considered with this small population (n = 9) as shown by Mann–Whitney U-test (Z = 1·9, 95% confidence). The uncertainty expected in this region due to geometry (volume) changes is up to 9% higher for volumes from 225·9 cc to 968·8 cc. According to the treatment techniques and in vivo dosimetry, the contralateral breast skin dose was 1·0% in FIF and 2·5% in VMAT concerning the prescribed dose.

Conclusion:

There is no difference in skin dosimetry between VMAT and FIF techniques on the ipsilateral breast. It provides useful support for the use of VMAT as a planning technique for breast irradiation. The work describes the importance of quantifying potential differences in skin dosimetry.

Tanshinone IIA Accomplished Protection against Radiation-Induced Cardiomyocyte Injury by Regulating the p38/p53 Pathway

Background

Radiotherapy is one of the major strategies for treating tumors, and it inevitably causes damage to relevant tissues and organs during treatment. Radiation-induced heart disease (RIHD) refers to radiation-induced cardiovascular adverse effects caused by thoracic radiotherapy. Currently, there is no uniform standard in the treatment of RIHD.

Methods

In our group study, by administering a dose of 4 Gy radiation, we established a radiation injured cardiomyocyte model and explored the regulatory relationship between tanshinone IIA and p38 MAPK in cardiomyocyte injury. We assessed cell damage and proliferation using clonogenic assay and lactate dehydrogenase (LDH) release assay. The measures of antioxidant activity and oxidative stress were conducted using superoxide dismutase (SOD) and reactive oxygen species (ROS). The apoptosis rate and the relative expression of apoptotic proteins were conducted using flow cytometry and western blot. To assess p38 and p53 expressions and phosphorylation levels, western blot was performed.

Results

Experimental results suggested that tanshinone IIA restored cell proliferation in radiation-induced cardiomyocyte injury (∗∗P < 0.01), and the level of LDH release decreased (∗P < 0.05). Meanwhile, tanshinone IIA could decrease the ROS generation induced by radiation (∗∗P < 0.01) and upregulate the SOD level (∗∗P < 0.01). Again, tanshinone IIA reduced radiation-induced cardiomyocyte apoptosis (∗∗P < 0.01). Finally, tanshinone IIA downregulated radiation-induced p38/p53 overexpression (∗∗∗P < 0.001).

Conclusions

The treatment effects of tanshinone IIA against radiation-induced myocardial injury may be through the regulation of the p38/p53 pathway.

Breast cancer radiotherapy and the risk of acute coronary events - insights from a process oriented model

BACKGROUND AND PURPOSE

Acute coronary events (ACEs) are considered the most important side effect of radiotherapy (RT) for breast cancer but underlying mechanisms still have to be identified. Process oriented models mathematically describe the development of disease and provide a link between mechanisms and subsequent risk. Here, this link is exploited to learn about the underlying mechanisms from the observed age-time patterns of ACE risk.

MATERIALS AND METHODS

A process oriented model of atherosclerosis and subsequent ACEs was applied to a contemporary breast cancer cohort of 810 patients with measurements of coronary artery calcification. Patients with prior ischemic heart disease were excluded. The process oriented model describes disease development as a series of different stages. Different variants of the model were fitted to the data. In each variant, one stage was assumed to be accelerated in relation to mean heart dose.

RESULTS

During a mean follow up of 9.1 years, 25 ACEs occurred. The model reproduced the prevalence and associated risk of coronary calcifications. Mean heart dose significantly improved the fit only when implemented as affecting a late stage of atherosclerosis on already existing, complicated lesions (achieving p = 0.007). This can be understood by atherosclerosis being a slowly progressing disease. Therefore, an increase of ACEs few years after RT requires advanced atherosclerosis at the time of RT.

CONCLUSION

Risk of ACE increases within few years in patients with advanced atherosclerosis at RT. Therefore, patients should be assessed for cardiovascular risk, and also elderly patients need to be considered for heart sparing techniques.

A systems radiation biology approach to unravel the role of chronic low-dose-rate gamma-irradiation in inducing premature senescence in endothelial cells

Purpose

The aim of this study was to explore the effects of chronic low-dose-rate gamma-radiation at a multi-scale level. The specific objective was to obtain an overall view of the endothelial cell response, by integrating previously published data on different cellular endpoints and highlighting possible different mechanisms underpinning radiation-induced senescence.

Materials and methods

Different datasets were collected regarding experiments on human umbilical vein endothelial cells (HUVECs) which were chronically exposed to low dose rates (0, 1.4, 2.1 and 4.1 mGy/h) of gamma-rays until cell replication was arrested. Such exposed cells were analyzed for different complementary endpoints at distinct time points (up to several weeks), investigating cellular functions such as proliferation, senescence and angiogenic properties, as well as using transcriptomics and proteomics profiling. A mathematical model was proposed to describe proliferation and senescence.

Results

Simultaneous ceasing of cell proliferation and senescence onset as a function of time were well reproduced by the logistic growth curve, conveying shared equilibria between the two endpoints. The combination of all the different endpoints investigated highlighted a dose-dependence for prematurely induced senescence. However, the underpinning molecular mechanisms appeared to be dissimilar for the different dose rates, thus suggesting a more complex scenario.

Conclusions

This study was conducted integrating different datasets, focusing on their temporal dynamics, and using a systems biology approach. Results of our analysis highlight that different dose rates have different effects in inducing premature senescence, and that the total cumulative absorbed dose also plays an important role in accelerating endothelial cell senescence.

Pyrrolidine Dithiocarbamate Might Mitigate Radiation-Induced Heart Damage at an Early Stage in Rats

Objective: Radiation-induced heart damage (RIHD) is becoming an increasing concern due to offsetting clinical benefits of radiotherapy to a certain extent. Pyrrolidine dithiocarbamate (PDTC) as an antioxidant has been implicated in cardioprotective effects. We aimed to investigate whether pyrrolidine dithiocarbamate could attenuate heart damage at an early stage post-irradiation and unveil the potential mechanisms. Methods: A total of 15 adult male Sprague-Dawley rats were randomized into the control, irradiation (IR), and PDTC plus irradiation (PDTC + IR) groups. Hearts were irradiated with a single fraction of 20.0 Gy. Rats received daily intraperitoneal injection of PDTC for 14 days. At the 14th day post-irradiation, echocardiography was performed, and rats were killed. Morphological damage was examined by hematoxylin-eosin (HE) stain and Masson's trichrome stain. The collagen volume fraction (CVF) was applied for semi-quantitative analysis. The protein levels were analyzed by Western blot and mRNA levels by quantitative real-time PCR. Results: No significant damage to systolic function of left ventricular was induced at an early stage post-irradiation. HE staining of cardiac tissue showed that the disordered arrangement of myocardial cells and abnormal cell infiltration were alleviated in the PDTC + IR group. The increased CVF in the irradiation group was inhibited in the PDTC + IR group (22.05 ± 2.64% vs. 9.99 ± 1.65%, p < 0.05). The protein levels of nuclear factor-kappa B (NF-κB), hypoxia-inducible factor-1α (HIF-1α), and COL-1 were downregulated after treatment with PDTC (p < 0.05), and there was a declining trend in the protein of the connective tissue growth factor (CTGF). The mRNA expression of NF-κB and HIF-1α in the PDTC plus irradiation group was lower than that in the irradiation group (p < 0.05), and there was a declining trend in the mRNA expression of the connective tissue growth factor and COL-1. Conclusion: PDTC alleviates myocardial cell disordered arrangement, abnormal cell infiltration, and pro-fibrotic change at an early stage in rats with radiation-induced heart damage. Such a protective effect is closely associated with the downregulation of NF-κB.

Cardiovascular ramifications of therapy-induced endothelial cell senescence in cancer survivors

Cancer survivorship has remarkably improved over the past decades; nevertheless, cancer survivors are burdened with multiple health complications primarily caused by their cancer therapy. Therapy-induced senescence is recognized as a fundamental mechanism contributing to adverse health complications in cancer survivors. In this mini-review, we will discuss the recent literature describing the mechanisms of cancer therapy-induced senescence. We will focus on endothelial cell senescence since it has been shown to be a key player in numerous cardiovascular complications. We will also discuss novel senotherapeutic approaches that have the potential to combat therapy-induced endothelial cell senescence.

How to Improve SBRT Outcomes in NSCLC: From Pre-Clinical Modeling to Successful Clinical Translation

Simple Summary

Despite major research and clinical efforts, lung cancer remains the leading cause of cancer-related death. Stereotactic body radiotherapy (SBRT) has emerged as a major treatment modality for lung cancer in the last decade. Additional research is needed to elucidate underlying mechanisms of resistance and to develop improved therapeutic strategies. Clinical progress relies on accurate preclinical modelling of human disease in order to yield clinically meaningful results; however, successful translation of pre-clinical research is still lagging behind. In this review, we summarize the major clinical developments of radiation therapy for non-small-cell lung cancer (NSCLC), and we discuss the pre-clinical research models at our disposal, highlighting ongoing translational challenges and future perspectives.

Abstract

Despite major research and clinical efforts, lung cancer remains the leading cause of cancer-related death. While the delivery of conformal radiotherapy and image guidance of stereotactic body radiotherapy (SBRT) have revolutionized the treatment of early-stage non-small-cell lung cancer (NSCLC), additional research is needed to elucidate underlying mechanisms of resistance and identify novel therapeutic combinations. Clinical progress relies on the successful translation of pre-clinical work, which so far has not always yielded expected results. Improved clinical modelling involves characterizing the preclinical models and selecting appropriate experimental designs that faithfully mimic precise clinical scenarios. Here, we review the current role of SBRT and the scope of pre-clinical armamentarium at our disposal to improve successful clinical translation of pre-clinical research in the radiation oncology of NSCLC.

Lisinopril Mitigates Radiation-Induced Mitochondrial Defects in Rat Heart and Blood Cells

The genetic bases and disparate responses to radiotherapy are poorly understood, especially for cardiotoxicity resulting from treatment of thoracic tumors. Preclinical animal models such as the Dahl salt-sensitive (SS) rat can serve as a surrogate model for salt-sensitive low renin hypertension, common to African Americans, where aldosterone contributes to hypertension-related alterations of peripheral vascular and renal vascular function. Brown Norway (BN) rats, in comparison, are a normotensive control group, while consomic SSBN6 with substitution of rat chromosome 6 (homologous to human chromosome 14) on an SS background manifests cardioprotection and mitochondrial preservation to SS rats after injury. In this study, 2 groups from each of the 3 rat strains had their hearts irradiated (8 Gy X 5 fractions). One irradiated group was treated with the ACE-inhibitor lisinopril, and a separate group in each strain served as nonirradiated controls. Radiation reduced cardiac end diastolic volume by 9-11% and increased thickness of the interventricular septum (11-16%) and left ventricular posterior wall (14-15%) in all 3 strains (5-10 rats/group) after 120 days. Lisinopril mitigated the increase in posterior wall thickness. Mitochondrial function was measured by the Seahorse Cell Mitochondrial Stress test in peripheral blood mononuclear cells (PBMC) at 90 days. Radiation did not alter mitochondrial respiration in PBMC from BN or SSBN6. However, maximal mitochondrial respiration and spare capacity were reduced by radiation in PBMC from SS rats (p=0.016 and 0.002 respectively, 9-10 rats/group) and this effect was mitigated by lisinopril (p=0.04 and 0.023 respectively, 9-10 rats/group). Taken together, these results indicate injury to the heart by radiation in all 3 strains of rats, although the SS rats had greater susceptibility for mitochondrial dysfunction. Lisinopril mitigated injury independent of genetic background.

The Impact of Radiation Dose to Heart Substructures on Major Coronary Events and Patient Survival after Chemoradiation Therapy for Esophageal Cancer

Background: There is a paucity of data regarding the association between radiation exposure of heart substructures and the incidence of major coronary events (MCEs) in patients with esophageal cancer (ESOC) undergoing chemoradiation therapy. We studied radiation dosimetric determinants of MCE risk and measured their impact on patient prognosis using a cohort of ESOC patients treated at a single institution. Methods: Between March 2005 and October 2015, 355 ESOC patients treated with concurrent chemoradiotherapy were identified from a prospectively maintained and institutional-regulatory-board-approved clinical database. Dose-distribution parameters of the whole heart, the atria, the ventricles, the left main coronary artery, and three main coronary arteries were extracted for analysis. Results: Within a median follow-up time of 67 months, 14 patients experienced MCEs at a median of 16 months. The incidence of MCEs was significantly associated with the left anterior descending coronary artery (LAD) receiving ≥30 Gy (V30Gy) (p = 0.048). Patients receiving LAD V30Gy ≥ 10% of volume experienced a higher incidence of MCEs versus the LAD V30Gy < 10% group (p = 0.044). The relative rate of death increased with the left main coronary artery (LMA) mean dose (Gy) (p = 0.002). Furthermore, a mutual promotion effect of hyperlipidemia and RT on MCEs was observed. Conclusion: Radiation dose to coronary substructures is associated with MCEs and overall survival in patients with ESOC. In this study, the doses to these substructures appeared to be better predictors of toxicity outcomes than mean heart dose (MHD) or whole-heart V30Gy. These findings have implications for reducing coronary events through radiation therapy planning.

Incidence risks for cerebrovascular diseases and types of stroke in a cohort of Mayak PA workers

Incidence risks for cerebrovascular diseases (CeVD) and some types of stroke in a cohort of 22,377 Russian Mayak nuclear workers chronically exposed to ionising radiation and followed up until the end of 2018 are reported. Among total 9469 cases of CeVD, 2078 cases were strokes that included 262 hemorrhagic strokes (HS) and 1611 ischemic strokes (IS). Data evaluation was performed with categorical and dose-response analyses estimating the relative risk (RR) and excess relative risk (ERR) per unit cumulative liver absorbed dose of external gamma-ray or internal alpha-particle exposure based on a linear model utilizing the AMFIT module of the EPICURE software. CeVD incidence was found to be significantly associated with cumulative radiation dose: ERR/Gy was 0.37 (95% confidence interval (CI) 0.27, 0.47) in males and 0.47 (95% CI 0.31, 0.66) in females for external exposure, and 0.31 (95% CI 0.11, 0.59) in males and 0.32 (95% CI 0.11, 0.61) in females for internal exposure. When the model for the analysis of external radiation effect did not include an adjustment for alpha radiation dose (and vice versa), the radiogenic risk estimate increased notably both for males and for females. In contrast, exclusion from or inclusion in the model of additional adjustments for non-radiation factors did not notably change the risk estimates. ERR/Gy of external gamma dose for CeVD incidence significantly decreased with increasing attained age (males and females) and duration of employment (females). No significant associations of either stroke or its types with cumulative gamma-ray dose of external exposure or alpha-particle dose of internal exposure were found.

Nuclear medicine imaging methods of radiation-induced cardiotoxicity

Breast cancer survival is significantly improved over the past decades due to major improvements in anti-tumor therapies and the implementation of regular screening, which leads to early detection of breast cancer. Therefore, it is of utmost importance to prevent patients from long-term side effects, including radiotherapy-induced cardiotoxicity. Radiotherapy may contribute to damage of myocardial structures on the cellular level, which eventually could result in various types of cardiovascular problems, including coronary artery disease and (non-)ischemic cardiomyopathy, leading to heart failure. These cardiac complications of radiotherapy are preceded by alterations in myocardial perfusion and blood flow. Therefore, early detection of these alterations is important to prevent the progression of these pathophysiological processes. Several radionuclide imaging techniques may contribute to the early detection of these changes. Single-Photon Emission Computed Tomography (SPECT) cameras can be used to create Multigated Acquisition scans in order to assess the left ventricular systolic and diastolic function. Furthermore, SPECT cameras are used for myocardial perfusion imaging with radiopharmaceuticals such as ^99mTc-sestamibi and ^99mTc-tetrofosmin. Accurate quantitative measurement of myocardial blood flow (MBF), can be performed by Positron Emission Tomography (PET), as the uptake of some of the tracers used for PET-based MBF measurement almost creates a linear relationship with MBF, resulting in very accurate blood flow quantification. Furthermore, there are PET and SPECT tracers that can assess inflammation and denervation of the cardiac sympathetic nervous system. Research over the past decades has mainly focused on the long-term development of left ventricular impairment and perfusion defects. Considering laterality of the breast cancer, some early studies have shown that women irradiated for left-sided breast cancer are more prone to cardiotoxic side effects than women irradiated for right-sided breast cancer. The left-sided radiation field in these trials, which predominantly used older radiotherapy techniques without heart-sparing techniques, included a larger volume of the heart and left ventricle, leading to increased unavoidable radiation exposure to the heart due to the close proximity of the radiation treatment volume. Although radiotherapy for breast cancer exposes the heart to incidental radiation, several improvements and technical developments over the last decades resulted in continuous reduction of radiation dose and volume exposure to the heart. In addition, radiotherapy reduces loco-regional tumor recurrences and death from breast cancer and improves survival. Therefore, in the majority of patients, the benefits of radiotherapy outweigh the potential very low risk of cardiovascular adverse events after radiotherapy. This review addresses existing nuclear imaging techniques, which can be used to evaluate (long-term) effects of radiotherapy-induced mechanical cardiac dysfunction and discusses the potential use of more novel nuclear imaging techniques, which are promising in the assessment of early signs of cardiac dysfunction in selected irradiated breast cancer patients.

Small animal models of localized heart irradiation

A subset of cancer patients treated with radiation therapy may experience radiation-induced heart disease (RIHD) that develops within weeks to several years after cancer treatment. Rodent models are most commonly used to examine the biological effects of local X-rays in the heart and test potential strategies to reduce RIHD. While developments in technology over the last decades have changed the procedures for local heart irradiation in animal models, the X-ray settings and radiation doses have remained quite consistent in time and between different research laboratories. This chapter provides a protocol for whole heart irradiation in rodent models, using an X-ray machine with cone beam computed tomography (CBCT) capabilities. Some methods for the quantification of common histological changes after whole heart irradiation in the rodent are also described.

Radiation-induced cardiovascular disease: an overlooked role for DNA methylation?

Radiotherapy in cancer treatment involves the use of ionizing radiation for cancer cell killing. Although radiotherapy has shown significant improvements on cancer recurrence and mortality, several radiation-induced adverse effects have been documented. Of these adverse effects, radiation-induced cardiovascular disease (CVD) is particularly prominent among patients receiving mediastinal radiotherapy, such as breast cancer and Hodgkin's lymphoma patients. A number of mechanisms of radiation-induced CVD pathogenesis have been proposed such as endothelial inflammatory activation, premature endothelial senescence, increased ROS and mitochondrial dysfunction. However, current research seems to point to a so-far unexamined and potentially novel involvement of epigenetics in radiation-induced CVD pathogenesis. Firstly, epigenetic mechanisms have been implicated in CVD pathophysiology. In addition, several studies have shown that ionizing radiation can cause epigenetic modifications, especially DNA methylation alterations. As a result, this review aims to provide a summary of the current literature linking DNA methylation to radiation-induced CVD and thereby explore DNA methylation as a possible contributor to radiation-induced CVD pathogenesis.

Bradyarrhythmias in Cardio-Oncology

The relationship between bradyarrhythmias and cancer therapies has not been well described but is increasingly recognized. There have been extensive advances in oncological pharmacotherapy, with several new classes of drugs available including targeted agents, immune checkpoint inhibitors and CAR T cell therapy. This increasing repertoire of available drugs has revolutionized overall prognosis and survival of cancer patients but the true extent of their cardiovascular toxicity is only beginning to be understood. Previous studies and published reviews have traditionally focused on conventional chemotherapies and in arrhythmias in general, particularly tachyarrhythmias. The number of patients with both cancer and cardiovascular problems is increasing globally and oncologists and cardiologists need to be adept at managing arrythmia based scenarios. Greater collaboration between the two specialties including studies with prospective data collection in Cardio-Oncology are much needed to fill in knowledge gaps in this arena. This case-based review summarizes current available evidence of cancer treatment-related bradyarrhythmia incidence (including its different subtypes), possible mechanisms and outcomes. Furthermore, we propose a stepwise surveillance and management protocol for patients with suspected bradyarrhythmia related to cancer treatment.

Cardiovascular risk in high-hazard occupations: the role of occupational cardiology

Work is beneficial for health, but many individuals develop cardiovascular disease (CVD) during their working lives. Occupational cardiology is an emerging field that combines traditional cardiology sub-specialisms with prevention and risk management unique to specific employment characteristics and conditions. In some occupational settings incapacitation through CVD has the potential to be catastrophic due to the nature of work and/or the working environment. These are often termed 'hazardous' or 'high-hazard' occupations. Consequently, many organizations that employ individuals in high-hazard roles undertake pre-employment medicals and periodic medical examinations to screen for CVD. The identification of CVD that exceeds predefined employer (or regulatory body) risk thresholds can result in occupational restriction, or disqualification, which may be temporary or permanent. This article will review the evidence related to occupational cardiology for several high-hazard occupations related to aviation and space, diving, high altitude, emergency workers, commercial transportation, and the military. The article will focus on environmental risk, screening, surveillance, and risk management for the prevention of events precipitated by CVD. Occupational cardiology is a challenging field that requires a broad understanding of general cardiology, environmental, and occupational medicine principles. There is a current lack of consensus and contemporary evidence which requires further research. Provision of evidence-based, but individualized, risk stratification and treatment plans is required from specialists that understand the complex interaction between work and the cardiovascular system. There is a current lack of consensus and contemporary evidence in occupational cardiology and further research is required.

Antioxidant Potential and Inhibition of Mitochondrial Permeability Transition Pore by Myricetin Reduces Aluminium Phosphide-Induced Cytotoxicity and Mitochondrial Impairments

Oxidative stress and mitochondrial dysfunction are involved in the mechanisms of cardiac toxicity induced by aluminum phosphide (AlP). AlP-induced cardiotoxicity leads to cardiomyocyte death, cardiomyopathy, cardiac dysfunction, and eventually severe heart failure and death. Importantly, protecting cardiomyocytes from death resulting from AlP is vital for improving survival. It has been reported that flavonoids such as myricetin (Myr) act as modifiers of mitochondrial function and prevent mitochondrial damage resulting from many insults and subsequent cell dysfunction. In this study, the ameliorative effect of Myr, as an important antioxidant and mitochondrial protective agent, was investigated in cardiomyocytes and mitochondria isolated from rat heart against AlP-induced toxicity, oxidative stress, and mitochondrial dysfunction. Treatment of AlP (20 μg/ml) significantly increased cytotoxicity; reduced glutathione (GSH) depletion, cellular reactive oxygen species (ROS) formation, malondialdehyde (MDA) level, ATP depletion, caspase-3 activation, mitochondrial membrane potential (ΔΨm) collapse, and lysosomal dysfunction; and decreased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in intact cardiomyocytes. Also, treatment of AlP (20 μg/ml) significantly increased mitochondrial dysfunction and swelling in isolated mitochondria. Myr (80 µM) appeared to ameliorate AlP-induced cytotoxicity in isolated cardiomyocytes; significantly lessened the AlP-stimulated intracellular ROS and MDA production and depletion of GSH; and increased the activities of SOD, CAT, and GSH-Px. Furthermore, Myr (40 and 80 µM) lowered AlP-induced lysosomal/mitochondrial dysfunction, ATP depletion, and caspase-3 activation. In the light of these findings, we concluded that Myr through antioxidant potential and inhibition of mitochondrial permeability transition (MPT) pore exerted an ameliorative role in AlP-induced toxicity in isolated cardiomyocytes and mitochondria, and it would be valuable to examine its in vivo effects.

Investigation of the Antihypertrophic and Antifibrotic Effects of Losartan in a Rat Model of Radiation-Induced Heart Disease

Radiation-induced heart disease (RIHD) is a potential late side-effect of thoracic radiotherapy resulting in left ventricular hypertrophy (LVH) and fibrosis due to a complex pathomechanism leading to heart failure. Angiotensin-II receptor blockers (ARBs), including losartan, are frequently used to control heart failure of various etiologies. Preclinical evidence is lacking on the anti-remodeling effects of ARBs in RIHD, while the results of clinical studies are controversial. We aimed at investigating the effects of losartan in a rat model of RIHD. Male Sprague-Dawley rats were studied in three groups: (1) control, (2) radiotherapy (RT) only, (3) RT treated with losartan (per os 10 mg/kg/day), and were followed for 1, 3, or 15 weeks. At 15 weeks post-irradiation, losartan alleviated the echocardiographic and histological signs of LVH and fibrosis and reduced the overexpression of chymase, connective tissue growth factor, and transforming growth factor-beta in the myocardium measured by qPCR; likewise, the level of the SMAD2/3 protein determined by Western blot decreased. In both RT groups, the pro-survival phospho-AKT/AKT and the phospho-ERK1,2/ERK1,2 ratios were increased at week 15. The antiremodeling effects of losartan seem to be associated with the repression of chymase and several elements of the TGF-β/SMAD signaling pathway in our RIHD model.

Stereotactic radioablation for ventricular tachycardia

Non-invasive stereotactic radioablation of ventricular tachycardia (VT) substrate has been proposed as a novel treatment modality for patients not eligible for catheter-based ablation or in whom this approach has failed. Initial clinical results are promising with good short-term efficacy in VT suppression and tolerable side effects. This article reviews the current clinical evidence for cardiac radioablation and gives an overview of important preclinical and translational results. Practical guidance is provided, and a cardiac radioablation planning and treatment workflow based on expert consensus and the authors' institutional experience is set out.

Assessment of Prognostic Value of High-Sensitivity Cardiac Troponin T for Early Prediction of Chemoradiation Therapy-Induced Cardiotoxicity in Patients with Non-Small Cell Lung Cancer: A Secondary Analysis of a Prospective Randomized Trial

PURPOSE

Cardiotoxicities induced by cancer therapy can negatively affect quality of life and survival. We investigated whether high-sensitivity cardiac troponin T (hs-cTnT) levels could serve as biomarker for early detection of cardiac adverse events (CAEs) after chemoradiation therapy (CRT) for non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

This study included 225 patients who received concurrent platinum and taxane-doublet chemotherapy with thoracic radiation therapy to a total dose of 60 to 74 Gy for NSCLC. All patients were evaluated for CAEs; 190 patients also had serial hs-cTnT measurements.

RESULTS

Grade ≥3 CAEs occurred in 24 patients (11%) at a median interval of 9 months after CRT. Pretreatment hs-cTnT levels were higher in men, in patients aged ≥64 years, and in patients with pre-existing heart disease or poor performance status (P < .05). hs-cTnT levels increased at 4 weeks during CRT (P < .05) and decreased after completion of CRT but did not return to pretreatment levels (P = .002). The change (Δ) in hs-cTnT levels during CRT correlated with mean heart dose (P = .0004), the heart volumes receiving 5 to 55 Gy (P < .05), and tumor location (P = .006). Risks of severe CAEs and mortality were significantly increased if the pretreatment hs-cTnT was >10 ng/L or the Δ during CRT was ≥5 ng/L.

CONCLUSIONS

Elevation of hs-cTnT during CRT was radiation heart dose-dependent, and high hs-cTnT levels during the course of CRT were associated with CAEs and mortality. Routine monitoring of hs-cTnT could identify patients who are at high risk of CRT-induced CAEs early to guide modifications of cancer therapy and possible interventions to mitigate cardiotoxicity.

The Importance of Primary Care in Cardio-Oncology

OPINION STATEMENT

There is significant interplay between cancer and cardiovascular disease involving shared risk factors, cross disease communication where cardiovascular events can influence cancer recurrence, and mortality rates and cardiotoxicity from cancer treatments with resultant increased cardiovascular mortality and morbidity in cancer patients. This is a major cause of death in many long-term cancer survivors. As a result, cardio-oncology, which involves the prevention, early detection, and optimal treatment of cardiovascular disease in patients treated for cancer, is expanding globally. However, there is still limited awareness of its importance and limited application of the lessons already learnt. Primary care physicians, and their clinical teams, especially nursing colleagues, have a foundation role in the management of all patients, and this paper outlines areas where they can lead in the cardio-oncology management of cancer patients. Although there is currently a lack of an adequate clinical framework or shared care plan, primary care physicians have a role to play in the various phases of cancer treatment: pre-therapy, during therapy, and survivorship.

Cardiovascular Manifestations From Therapeutic Radiation: A Multidisciplinary Expert Consensus Statement From the International Cardio-Oncology Society

Radiation therapy is a cornerstone of cancer therapy, with >50% of patients undergoing therapeutic radiation. As a result of widespread use and improved survival, there is increasing focus on the potential long-term effects of ionizing radiation, especially cardiovascular toxicity. Radiation therapy can lead to atherosclerosis of the vasculature as well as valvular, myocardial, and pericardial dysfunction. We present a consensus statement from the International Cardio-Oncology Society based on general principles of radiotherapy delivery and cardiovascular risk assessment and risk mitigation in this population. Anatomical-based recommendations for cardiovascular management and follow-up are provided, and a priority is given to the early detection of atherosclerotic vascular disease on imaging to help guide preventive therapy. Unique management considerations in radiation-induced cardiovascular disease are also discussed. Recommendations are based on the most current literature and represent a unanimous consensus by the multidisciplinary expert panel.

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Radiation therapy leads to short- and long-term cardiovascular adverse effects of the vasculature and the heart, including valvular, myocardial, and pericardial disease.

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Computed tomography scans conducted for radiation planning or cancer staging provide an available opportunity to detect asymptomatic atherosclerosis and direct preventive therapies.

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Additional practical screening recommendations for cardiovascular disease based on anatomical exposure are provided.

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There are unique considerations in the management of radiation-induced cardiovascular disease; contemporary percutaneous treatment is often preferred over surgical options.

A Human 3D Cardiomyocyte Risk Model to Study the Cardiotoxic Influence of X-rays and Other Noxae in Adults

The heart tissue is a potential target of various noxae contributing to the onset of cardiovascular diseases. However, underlying pathophysiological mechanisms are largely unknown. Human stem cell-derived models are promising, but a major concern is cell immaturity when estimating risks for adults. In this study, 3D aggregates of human embryonic stem cell-derived cardiomyocytes were cultivated for 300 days and characterized regarding degree of maturity, structure, and cell composition. Furthermore, effects of ionizing radiation (X-rays, 0.1–2 Gy) on matured aggregates were investigated, representing one of the noxae that are challenging to assess. Video-based functional analyses were correlated to changes in the proteome after irradiation. Cardiomyocytes reached maximum maturity after 100 days in cultivation, judged by α-actinin lengths, and displayed typical multinucleation and branching. At this time, aggregates contained all major cardiac cell types, proven by the patch-clamp technique. Matured and X-ray-irradiated aggregates revealed a subtle increase in beat rates and a more arrhythmic sequence of cellular depolarisation and repolarisation compared to non-irradiated sham controls. The proteome analysis provides first insights into signaling mechanisms contributing to cardiotoxicity. Here, we propose an in vitro model suitable to screen various noxae to target adult cardiotoxicity by preserving all the benefits of a 3D tissue culture.

Leveraging Radiobiology for Arrhythmia Management: A New Treatment Paradigm?

Radiation therapy is a well-established approach for safely and non-invasively treating solid tumours and benign diseases with high precision and accuracy. Cardiac radiation therapy has recently emerged as a non-invasive treatment option for the management of refractory ventricular tachycardia. Here we summarise existing clinical and preclinical literature surrounding cardiac radiobiology and discuss how these studies may inform basic and translational research, as well as clinical treatment paradigms in the management of arrhythmias.

Cardiac Magnetic Resonance Imaging and Blood Biomarkers for Evaluation of Radiation-Induced Cardiotoxicity in Patients With Breast Cancer: Results of a Phase 2 Clinical Trial

PURPOSE

Radiation therapy (RT) can increase the risk of cardiac events in patients with breast cancer (BC), but biomarkers predicting risk for developing RT-induced cardiac disease are currently lacking. We report results from a prospective clinical trial evaluating early magnetic resonance imaging (MRI) and serum biomarker changes as predictors of cardiac injury and risk of subsequent cardiac events after RT for left-sided disease.

METHODS

Women with node-negative and node-positive (N-/+) left-sided BC were enrolled on 2 institutional review board (IRB)-approved protocols at 2 institutions. MRI was conducted pretreatment (within 1 week of starting radiation), at the end of treatment (last day of treatment ±1 week), and 3 months after the last day of treatment (±2 weeks) to quantify left and right ventricular volumes and function, myocardial fibrosis, and edema. Perfusion changes during regadenoson stress perfusion were also assessed on a subset of patients (n = 28). Serum was collected at the same time points. Whole heart and cardiac substructures were contoured using CT and MRI. Models were constructed using baseline cardiac and clinical risk factors. Associations between MRI-measured changes and dose were evaluated.

RESULTS

Among 51 women enrolled, mean heart dose ranged from 0.80 to 4.7 Gy and mean left ventricular (LV) dose from 1.1 to 8.2 Gy, with mean heart dose 2.0 Gy. T1 time, a marker of fibrosis, and right ventricular (RV) ejection fraction (EF) significantly changed with treatment; these were not dose dependent. T2 (marker of edema) and LV EF did not significantly change. No risk factors were associated with baseline global perfusion. Prior receipt of doxorubicin was marginally associated with decreased myocardial perfusion after RT (P = .059), and mean MHD was not associated with perfusion changes. A significant correlation between baseline IL-6 and mean heart dose (MHD) at the end of RT (ρ 0.44, P = .007) and a strong trend between troponin I and MHD at 3 months post-treatment (ρ 0.33, P = .07) were observed. No other significant correlations were identified.

CONCLUSIONS

In this prospective study of women with left-sided breast cancer treated with contemporary treatment planning, cardiac radiation doses were very low relative to historical doses reported by Darby et al. Although we observed significant changes in T1 and RV EF shortly after RT, these changes were not correlated with whole heart or substructure doses. Serum biomarker analysis of cardiac injury demonstrates an interesting trend between markers and MHD that warrants further investigation.