Radio-induced cardiotoxicity: From physiopathology and risk factors to adaptation of radiotherapy treatment planning and recommended cardiac follow-up

Heart and lung sparing with isocentric lateral decubitus positioning compared with dorsal decubitus positioning during adjuvant localized breast cancer radiotherapy

OBJECTIVES

The cardiac and pulmonary dosimetric benefit of alternative positioning in isocentric lateral decubitus compared with dorsal decubitus during adjuvant breast irradiation has yet to be proven, in spite of the relative long-standing use of isocentric lateral decubitus.

METHODS

Eight consecutive patients with an indication for adjuvant breast irradiation without boost or lymph node irradiation were scanned in both isocentric lateral and dorsal decubitus positions. For each patient, a plan delivering 40.05 Gy in 15 fractions in isocentric lateral decubitus and in dorsal decubitus using a field-in-field technique was calculated. Doses to the heart, to various cardiac substructures, and to the lungs were compared.

RESULTS

Mean dose to the heart, to various cardiac structures (left ventricle, left coronary, right coronary), to the homolateral lung, and to the contralateral lung were significantly lower in isocentric lateral decubitus than in dorsal decubitus. Average absolute mean dose reductions were -40 cGy for the heart, -27.5 cGy for the left ventricle, -56.5 cGy for the right coronary artery, -64.5 cGy for the left coronary artery, -45.5 cGy for the sinoatrial node, -74 cGy for the homolateral lung, and -4.5 cGy for the contralateral lung. For all organs at risk, median dose-volume histograms in isocentric lateral decubitus showed lower relative volumes than in dorsal decubitus.

CONCLUSION

Lateral decubitus positioning significantly reduces dose to the heart, to various cardiac substructures, to the homolateral lung, and to the contralateral lung, compared with dorsal decubitus. This technique is easily implemented and can be widely recommended to reduce heart and lung doses to a minimum.

ADVANCES IN KNOWLEDGE

Lateral decubitus positioning significantly reduces dose to the heart, to various cardiac substructures, to the homolateral lung, and to the contralateral lung, compared with dorsal decubitus. This technique is easily implemented and can be widely recommended to reduce heart and lung doses to a minimum.

NADPH Oxidases in Cancer Therapy-Induced Cardiotoxicity: Mechanisms and Therapeutic Approaches

Cancer therapy-induced cardiotoxicity remains a significant clinical challenge, limiting the efficacy of cancer treatments and impacting long-term survival and quality of life. NADPH oxidases, a family of enzymes that are able to generate reactive oxygen species (ROS), have emerged as key players in the pathogenesis of cardiotoxicity associated with various cancer therapies. This review comprehensively examines the role of NADPH oxidases in cancer therapy-induced cardiotoxicity, elucidating the underlying mechanisms and exploring potential therapeutic approaches. We discuss the structure and function of NADPH oxidases in the cardiovascular system and their involvement in cardiotoxicity induced by anthracyclines and ionizing radiation. The molecular mechanisms by which NADPH oxidase-derived ROS contribute to cardiac injury are explored, including direct oxidative damage, activation of pro-apoptotic pathways, mitochondrial dysfunction, vascular damage, inflammation, fibrosis, and others. Furthermore, we evaluate therapeutic strategies targeting NADPH oxidases, such as specific inhibitors, antioxidant therapies, natural products, and other cardioprotectors. The review also addresses current challenges in the field, including the need for isoform-specific targeting and the identification of reliable biomarkers. Finally, we highlight future research directions aimed at mitigating NADPH oxidase-mediated cardiotoxicity and alleviating cardiovascular side effects in cancer survivors. By synthesizing current knowledge and identifying knowledge gaps, this review provides a rationale for future studies and the development of novel cardioprotective strategies in cancer therapy.

Assessment and stratification of cardiovascular disease risk in people diagnosed with breast cancer: A scoping review

BACKGROUND

Breast cancer patients are at increased risk of cardiovascular disease, which often are associated with cardiotoxic breast cancer treatment or overlapping risk factors between the two diseases. Pre-treatment cardiovascular risk assessment can enable accurate risk stratification and prevention of cardiovascular disease. Several tools have been suggested, described or used in research to assess baseline (pre-treatment) risk to determine appropriate cardiovascular disease care before, during and after cancer treatment. This scoping review aims to identify and describe key features of baseline cardiovascular disease risk assessment tools for breast cancer patients.

METHODS

PubMed, Embase and Google Scholar were searched for articles published January 2013 - March 2024 to identify publications reporting cardiovascular disease risk assessment tools in breast cancer patients. Publications included research articles (observational and experimental studies) and position/policy, commentary and review papers. Eligibility was assessed and key data were extracted independently by two reviewers. Conflicts were discussed and resolved with the authorship team.

RESULTS

A total 144 articles were identified. Of these, 57 reported original data for the development, validation or recommendations of cardiovascular disease risk assessment tools and 87 reported the use of such tools. From these articles, 13 tools were identified that assessed the risk of cardiovascular disease broadly (n = 3) or death due to cardiovascular disease (n = 1) or specifically of cardiotoxicity or heart failure (n = 8) or venous thromboembolism (n = 1) in people diagnosed with breast cancer. Fourteen tools assessed cardiovascular disease risk in people diagnosed with mixed cancer types, including breast cancer. The planned development of four tools and/or surveillance pathways were described in protocol papers. Among all these tools identified (n = 31), seven tools (among these, four tools assessed people diagnosed with breast cancer only) went through external validation and performed poorly or moderately in stratifying cancer patients effectively into risk categories. Risk factors included in the assessment tools were age, breast cancer treatment type and pre-existing cardiovascular disease. While clinical guidelines and recommendations about baseline cardiovascular disease risk assessment were identified, these were either for cancer patients broadly or for cancer treatment types, and not specifically for people diagnosed with breast cancer.

CONCLUSION

Several tools to assess baseline cardiovascular disease in people diagnosed with breast cancer were identified but only seven tools had gone through a validation process, and none were found to be very effective in differentiating people by baseline cardiovascular disease risk. Further work is needed to optimise the effectiveness of baseline cardiovascular disease risk assessments for breast cancer patients to enable appropriate stratification and monitoring of risk before, during and after treatment to improve cardiovascular health and outcomes.

Quantitative evaluation of radiation-induced heart disease in beagle dogs by speckle tracking echocardiography

OBJECTIVE

This study aimed to detect early changes in left ventricular systolic function in Beagle dogs after radiotherapy using two-dimensional speckle tracking echocardiography and to explore its potential value in evaluating radiation-induced heart disease.

METHODS

Thirty-six Beagle dogs were randomized into a control group (n = 18) and an irradiation group (n = 18). The irradiation group received a single dose of 20 Gy to the left ventricular anterior wall, while controls underwent sham irradiation. Conventional echocardiography and 2D speckle tracking echocardiography were performed at baseline and 3, 6, and 12 months post-procedure. Additionally, six dogs were randomly selected from each group and euthanized at 3-, 6-, and 12-month post-irradiation, and their hearts were collected for histopathological testing.

RESULTS

In the irradiation group, the global longitudinal strain of the left ventricle and regional strain in the irradiated area were significantly reduced versus baseline and controls by 3 months, with progressive decline at 6 and 12 months. Strain reduction correlated spatially with pathological injury. Conversely, there were no substantial differences in conventional echocardiographic parameters between the groups after 3 months. Conventional parameters (e.g., LVEF) showed differences only at later timepoints. Histopathology revealed progressive cardiomyocyte damage, fibrosis, and microvascular injury in irradiated regions, extending to the posterior wall by 12 months.

CONCLUSION

Two-dimensional speckle tracking echocardiography-derived strain parameters spatially correlate with radiation-induced pathological changes and detect subtle systolic dysfunction prior to irreversible remodeling. Speckle tracking may localize regions of peak radiation dose delivery.

Proton therapy reduces the effective dose to immune cells in breast cancer patients

BACKGROUND

The effective dose to circulating immune cells (EDIC) is associated with survival in lung and esophageal cancer patients. This study aimed to evaluate the benefit of intensity-modulated proton therapy (IMPT) for EDIC reduction as compared to volumetric modulated arc therapy (VMAT) in patients with locally advanced breast cancer (BC).

MATERIALS AND METHODS

Ten BC patients treated with locoregional VMAT after breast-conserving surgery were included. Mean dose to the heart (MHD), lungs (MLD), and liver (MlD), as well as the integral dose to the body (ITD), were retrieved, and we calculated EDIC as 0.12 × MLD + 0.08 × MHD + 0.15 × 0.85 × √(n/45) × MlD + (0.45 + 0.35 × 0.85 × √(n/45)) × ITD/(62 × 103), where n is the number of fractions. EDIC was compared between VMAT and IMPT plans.

RESULTS

Median EDIC was reduced from 3.37 Gy (range: 2.53-5.99) with VMAT to 2.13 Gy (1.31-3.77) with IMPT (p < 0.01). For left-sided BC patients, EDIC was reduced from 3.15 Gy (2.53-3.78) with VMAT to 1.65 Gy (1.31-3.77) with IMPT (p < 0.01). For right-sided BC patients, EDIC was reduced from 5.60 Gy (5.06-5.99) with VMAT to 3.38 Gy (3.10-3.77) with IMPT (p < 0.01). Right-sided BC patients had a higher EDIC irrespective of the technique. Integral dose reduction was the main driver of EDIC reduction with IMPT and was associated with lung sparing for left-sided BC patients or liver sparing for right-sided BC patients.

CONCLUSION

IMPT significantly reduced EDIC in BC patients undergoing locoregional adjuvant radiotherapy. Integral total dose reduction, associated with improved lung sparing in left-sided BC patients or liver sparing in right-sided BC patients, mainly drove EDIC reduction with IMPT. The emergence of dynamic models taking into account the circulatory kinetics of immune cells may improve the accuracy of the estimate of the dose received by the immune system compared to calculation of the EDIC, which is based solely on static dosimetric data.

Mechanisms of Cardiovascular Toxicities Induced by Cancer Therapies and Promising Biomarkers for Their Prediction: A Scoping Review

AIM

With the advancement of anti-cancer medicine, cardiovascular toxicities due to cancer therapies are common in oncology patients, resulting in increased mortality and economic burden. Cardiovascular toxicities caused by cancer therapies include different severities of cardiomyopathy, arrhythmia, myocardial ischaemia, hypertension, and thrombosis, which may lead to left ventricular dysfunction and heart failure. This scoping review aimed to summarise the mechanisms of cardiovascular toxicities following various anti-cancer treatments and potential predictive biomarkers for early detection.

METHODS

PubMed, Cochrane, Embase, Web of Science, Scopus, and CINAHL databases were searched for original studies written in English related to the mechanisms of cardiovascular toxicity induced by anti-cancer therapies, including chemotherapy, targeted therapy, immunotherapy, radiation therapy, and relevant biomarkers. The search and title/abstract screening were conducted independently by two reviewers, and the final analysed full texts achieved the consensus of the two reviewers.

RESULTS

A total of 240 studies were identified based on their titles and abstracts. In total, 107 full-text articles were included in the analysis. Cardiomyocyte and endothelial cell apoptosis caused by oxidative stress injury, activation of cell apoptosis, blocking of normal cardiovascular protection signalling pathways, overactivation of immune cells, and myocardial remodelling were the main mechanisms. Promising biomarkers for anti-cancer therapies related to cardiovascular toxicity included placental growth factor, microRNAs, galectin-3, and myeloperoxidase for the early detection of cardiovascular toxicity.

CONCLUSION

Understanding the mechanisms of cardiovascular toxicity following various anti-cancer treatments could provide implications for future personalised treatment methods to protect cardiovascular function. Furthermore, specific early sensitive and stable biomarkers of cardiovascular system damage need to be identified to predict reversible damage to the cardiovascular system and improve the effects of anti-cancer agents.

A bibliometric analysis of cardiotoxicity in cancer radiotherapy

Background

Radiotherapy, a primary treatment for malignant cancer, presents significant clinical challenges globally due to its associated adverse effects, especially with the increased survival rates of cancer patients. Radiation induced heart disease (RIHD) significantly impacts the long-term survival and quality of life of cancer survivors as one of the most devastating consequences. Quite a few studies have been conducted on preclinical and clinical trials of RIHD, showing promising success to some extent. However, no researchers have performed a comprehensive bibliometric study so far.

Objective

This study attempts to gain a deeper understanding of the focal points and patterns in RIHD research and to pinpoint prospective new research avenues using bibliometrics.

Methods

The study group obtained related 1554 publications between 1990 and 2023 on the Web of Science Core Collection (WOSCC) through a scientific search query. Visualization tools like CiteSpace and VOSviewer were utilized to realize the visual analysis of countries, authors, journals, references and keywords, identifying the hotspots and frontiers in this research field.

Results

After collecting all the data, a total of 1554 documents were categorized and analyzed using the above tools. The annual number of publications in the field of RIHD shows a continuous growth trend. In 2013, there was a significant rise in the number of linked publications, with the majority of authors being from the USA, according to the statistics. Among all the journals, INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS published the most relevant papers. Cluster analysis of the references showed that research on RIHD has focused on breast cancer, non-small cell lung cancer (NSCLC), and Hodgkin's lymphoma (also among the three main clusters), preclinical research, childhood cancer, heart dose, coronary artery disease, etc, which are also hot topics in the field. High-frequency keywords in the analysis include risk factors, cancer types, heart disease, survival, trials, proton therapy (PT), etc.

Conclusion

Future research on RIHD will mostly focus on thoracic cancer, whose exact cause is yet unknown, with preclinical trials playing an important role. Preventing, consistently monitoring, promptly diagnosing, and timely treating are crucial to decreasing RIHD and extending the life expectancy of cancer survivors.

Tolerance and Oncological Outcomes of In-Field Reirradiation for Locally Recurrent Breast Cancer: A Long-Term Single-Center Experience

BACKGROUND

The management of cancer relapse in previously irradiated tissues is a challenging therapeutic issue. The aim of this work was to report our experience with breast reirradiation for locoregionally recurrent breast cancer.

METHODS

All patients who underwent breast or chest wall in-field reirradiation at the Institut Curie, Paris, France, between 2003 and 2019, were identified. Efficacy outcomes and physician-reported toxicities were retrospectively assessed.

RESULTS

A total of 21,372 patients underwent breast irradiation in our institution. Of these, 28 received a second course of radiotherapy to the homolateral breast/chest wall. A total of 18 (64%) patients were treated with a curative intent, and 10 (36%) were treated for palliative purposes. Only one acute and one late grade 3 adverse events were reported. One patient with major cardiovascular risk factors died of myocardial infarction 13 months after left breast reirradiation. The 2-year LRFS, OS, DSS, PFS and MFS were 59%, 79%, 82%, 46% and 75%, respectively, in the whole cohort. The 2-year LRFS (72% vs. 31%, p = 0.02), OS (94% vs. 50%, p < 0.01), DSS (94% vs. 56%, p < 0.01) and PFS (61% vs. 20%, p = 0.02) differed significantly between patients treated with curative or palliative intent but not the MFS (78% vs. 69%, p = 0.77). Among the patients, eight (29%) remained relapse-free 5 years after reirradiation.

CONCLUSION

Breast/chest wall reirradiation appears to be feasible with good disease control, especially in patients treated with a curative intent, and presents acceptable toxicity rates.

Radiation Treatment Mechanisms of Cardiotoxicity: A Systematic Review

Radiotherapy may be used alone or in combination with chemotherapy for cancer treatment. There are many mechanisms of radiation treatment exposure to toxicities. Our aim was to summarize the literature about known mechanisms of radiation-induced cardiac toxicities. We performed a systematic review of the literature on the PubMed database until October 2022 about cardiovascular toxicities and radiation therapy exposure. Only systematic reviews, meta-analyses, and reviews were selected. Out of 1429 publications screened, 43 papers met inclusion criteria and were selected for the umbrella review process. Microvascular and macrovascular complications could lead to adverse cardiac effects. Many radiotherapy-associated risk factors were responsible, such as the site of radiation treatment, beam proximity to heart tissues, total dosage, the number of radiotherapy sessions, adjuvant chemotherapeutic agents used, and patient traditional cardiovascular risk factors, patient age, and gender. Moreover, important dosage cutoff values could increase the incidence of cardiac toxicities. Finally, the time from radiation exposure to cardiac side effects was assessed. Our report highlighted mechanisms, radiation dosage values, and the timeline of cardiovascular toxicities after radiation therapy. All of the above may be used for the assessment of cardiovascular risk factors and the development of screening programs for cancer patients.

Role and molecular mechanism of traditional Chinese medicine in preventing cardiotoxicity associated with chemoradiotherapy

Cardiotoxicity is a serious complication of cancer therapy. It is the second leading cause of morbidity and mortality in cancer survivors and is associated with a variety of factors, including oxidative stress, inflammation, apoptosis, autophagy, endoplasmic reticulum stress, and abnormal myocardial energy metabolism. A number of studies have shown that traditional Chinese medicine (TCM) can mitigate chemoradiotherapy-associated cardiotoxicity via these pathways. Therefore, this study reviews the effects and molecular mechanisms of TCM on chemoradiotherapy-related cardiotoxicity. In this study, we searched PubMed for basic studies on the anti-cardiotoxicity of TCM in the past 5 years and summarized their results. Angelica Sinensis, Astragalus membranaceus Bunge, Danshinone IIA sulfonate sodium (STS), Astragaloside (AS), Resveratrol, Ginsenoside, Quercetin, Danggui Buxue Decoction (DBD), Shengxian decoction (SXT), Compound Danshen Dripping Pill (CDDP), Qishen Huanwu Capsule (QSHWC), Angelica Sinensis and Astragalus membranaceus Bunge Ultrafiltration Extract (AS-AM),Shenmai injection (SMI), Xinmailong (XML), and nearly 60 other herbs, herbal monomers, herbal soups and herbal compound preparations were found to be effective as complementary or alternative treatments. These preparations reduced chemoradiotherapy-induced cardiotoxicity through various pathways such as anti-oxidative stress, anti-inflammation, alleviating endoplasmic reticulum stress, regulation of apoptosis and autophagy, and improvement of myocardial energy metabolism. However, few clinical trials have been conducted on these therapies, and these trials can provide stronger evidence-based support for TCM.

Quantifying Societal Burden of Radiation-Induced Cardiovascular Events in Breast Cancer Survivors

Background and Purpose

Radiation-induced cardiotoxicity is an important health concern for clinicians during treatment of breast cancer (BC) patients. Underlying mechanisms are well-documented, whereas little is known about the societal impact of this long-term effect. This study aimed to quantify the additional burden of radiation-induced cardiovascular (CV) diseases in BC survivors.

Materials and Methods

Conventional health economic modelling techniques were applied to estimate attributed CV-related costs and disutility in a hypothetical cohort of BC survivors. A situation in which radiotherapy caused an additional CV risk was compared with a situation in which this risk was not taken into account. Uncertainty was assessed via deterministic and probabilistic sensitivity analyses. Analyses were performed from a broad societal perspective up until 20 years after BC treatment.

Results

Radiation-induced cardiotoxicity evokes a mean incremental cost of €275.10 per woman over a time horizon of 20 years after BC treatment. An additional decrement of 0.017 QALYs (per woman) might be expected when taking the radiation-induced cardiotoxic risk into account in BC survivors. Incremental costs and disutility increased with age. A scenario analysis showed that these results were more profound in women with more advanced staging.

Conclusion

Our analyses suggest that with current radiation techniques, rather minor costs and disutility are to be expected from radiation-induced cardiotoxicity in BC survivors. The cost of past investments in order to achieve current mean heart dose (MHD) seems justified when considering the gains from cost and disutility reduction resulting from radiation-induced cardiovascular events. The question we might consider is whether future opportunity costs associated with investments on further technological advancements offset the expected marginal benefit from further reducing the MHD.

Radiation-Induced Heart Disease

Cancer incidence and survivorship have had a rising tendency over the last two decades due to better treatment modalities. One of these is radiation therapy (RT), which is used in 20-55% of cancer patients, and its basic principle consists of inhibiting proliferation or inducing apoptosis of cancer cells. Classically, photon beam RT has been the mainstay therapy for these patients, but, in the last decade, proton beam has been introduced as a new option. This newer method focuses more on the tumor and affects less of the surrounding normal tissue, i.e., the heart. Radiation to the heart is a common complication of RT, especially in patients with lymphoma, breast, lung, and esophageal cancer. The pathophysiology is due to changes in the microvascular and macrovascular milieu that can promote accelerated atherosclerosis and/or induce fibrosis of the myocardium, pericardium, and valves. These complications occur days, weeks, or years after RT and the risk factors associated are high radiation doses (>30 Gy), concomitant chemotherapy (primarily anthracyclines), age, history of heart disease, and the presence of cardiovascular risk factors. The understanding of these mechanisms and risk factors by physicians can lead to a tailored assessment and monitorization of these patients with the objective of early detection or prevention of radiation-induced heart disease. Echocardiography is a noninvasive method which provides a comprehensive evaluation of the pericardium, valves, myocardium, and coronaries, making it the first imaging tool in most cases; however, other modalities, such as computed tomography, nuclear medicine, or cardiac magnetic resonance, can provide additional value.

[Non-pharmalogical interventions and breast cancer: What benefit in addition to radiotherapy?]

Adjuvant radiotherapy is one of the major anticancer treatments in early breast cancer patients. Acute and late radio-induced effects may occur during or after breast cancer radiotherapy, and their medical management is a major issue for radiation oncologists. Here, the present review of literature embraces complementary non-pharmacological interventions, which could be combined to adjuvant radiotherapy in order to improve patients care.

Clinical practice of breast cancer protontherapy: A single-centre experience from selection to treatment

PURPOSE

Breast protontherapy efficiently limits cardiac, lung and contralateral breast exposure, which may clinically translate into better late tolerance profile compared with classic photon techniques. While breast protontherapy is already implemented in the United States and in some European countries, clinical experience of breast cancer protontherapy is currently limited in France. The aim of this study is to evaluate the clinical practice of breast cancer protontherapy at the Institut Curie in order to implement this technique at a larger scale.

MATERIALS AND METHODS

Data from all breast cancer patients that have been addressed to the protontherapy centre of Orsay (CPO, Institut Curie) for adjuvant breast protontherapy were retrieved. We analysed why these patients were ultimately treated with protontherapy or not.

RESULTS

Between November 2019 and November 2020, eleven breast cancer patients have been evaluated for adjuvant protontherapy at the CPO. Two of them were ultimately treated with proton beams; adjuvant breast protontherapy therapy was well tolerated. The nine other patients were not treated with protontherapy due to lack of availability of protontherapy treatment rooms in acceptable time limits, at the time of patient evaluation.

CONCLUSION

Despite dosimetric advantages and excellent clinical tolerance, lack of availability of protontherapy machines currently limits wider implementation of breast protontherapy.

Adjuvant Trastuzumab Emtansine (T-DM1) and Concurrent Radiotherapy for Residual Invasive HER2-positive Breast Cancer: Single-center Preliminary Results

OBJECTIVES

The treatment of nonmetastatic HER2-positive breast cancer with residual invasive disease using concurrent Trastuzumab emtansine (T-DM1) and radiotherapy appears to be an effective option. Our aim was to evaluate the acute side effects of this treatment regime.

METHODS

Fourteen patients were treated between March 2019 and April 2020 concurrent T-DM1 and radiotherapy. Left ventricular ejection fraction was assessed at baseline, before and after radiotherapy. All toxicities were evaluated using Common Terminology Criteria of Adverse Events (CTCAE) version 3.0.

RESULTS

The median age was 55 years (range 36 to 72). All patients received total dose of 50 Gy for the breast/ chest wall, 10 patients got lymph node irradiation, 4 patients received an additional tumor bed boost. The most common side effect was grade 1 radiodermatitis. A reversible grade 2 left ventricular ejection fraction decrease occurred in 2 patients. During our examination 3 patients showed alanine aminotransferases increase after the cycle 4 of T-DM1, 1 patient had grade 1, 1 patient grade 2, and 1 patient grade 3 alanine aminotransferase increases.

CONCLUSIONS

The acute toxicity rate especially focusing on skin and cardiac toxicity were assumed acceptable in our cohort. To safely administer this concomitant treatment, further examination and prospective data are needed.

Risk of Cardiac Disease in Patients With Breast Cancer: Impact of Patient-Specific Factors and Individual Heart Dose From Three-Dimensional Radiation Therapy Planning

PURPOSE

This retrospective cohort study aimed to determine whether adjuvant radiation therapy increases the risk of cardiac toxicity in Asian women with breast cancer, with a focus on patient-specific factors.

METHODS AND MATERIALS

We evaluated women who underwent primary breast surgery for breast cancer with (n = 520) or without (n = 774) adjuvant radiation therapy between January 2005 and May 2013. Patients who underwent breast surgery without radiation therapy were categorized as patients who received 0 Gy to the heart. The primary endpoint was the occurrence of a breast cancer treatment-related heart disease (BCT-HD), defined as a diagnosis of angina pectoris, unstable angina, myocardial infarction, ischemic heart disease, heart failure, or atrial fibrillation.

RESULTS

In total, 1294 patients were included. The overall 5- and 10-year BCT-HD rates were 2.4% and 5.7%, respectively. The risk of an BCT-HD significantly increased per 1-Gy increase in the mean heart dose (adjusted hazard ratio: 1.23). Additionally, histories of hypertension (hazard ratio: 1.92), and diabetes (hazard ratio: 2.51) were found to be adverse risk factors, whereas regular physical exercise (hazard ratio: 0.17) was a protective factor. Subgroup analysis according to risk groups showed that the effect of increasing mean heart dose (per Gy) was similar between women without or with minimal risk factors (hazard ratio: 1.23) and women with multiple risk factors (hazard ratio: 1.27).

CONCLUSIONS

The results indicate a radiation dose-effect relationship for cardiac disease in breast cancer patients, highlighting that there remains a considerable risk of cardiac toxicity even with 3-dimensional radiation therapy planning. Thus, measures to minimize the heart dose in breast cancer patients undergoing adjuvant radiation therapy, even in those without any risk factor for cardiac disease, should be routinely implemented.