Prognostic and Added Value of Echocardiographic Strain for Prediction of Adverse Outcomes in Patients with Locally Advanced Non-Small Cell Lung Cancer after Radiotherapy

Consequences of ionizing radiation exposure to the cardiovascular system

Ionizing radiation is widely used in various industrial and medical applications, resulting in increased exposure for certain populations. Lessons from radiation accidents and occupational exposure have highlighted the cardiovascular and cerebrovascular risks associated with radiation exposure. In addition, radiation therapy for cancer has been linked to numerous cardiovascular complications, depending on the distribution of the dose by volume in the heart and other relevant target tissues in the circulatory system. The manifestation of symptoms is influenced by numerous factors, and distinct cardiac complications have previously been observed in different groups of patients with cancer undergoing radiation therapy. However, in contemporary radiation therapy, advances in treatment planning with conformal radiation delivery have markedly reduced the mean heart dose and volume of exposure, and these variables are therefore no longer sole surrogates for predicting the risk of specific types of heart disease. Nevertheless, certain cardiac substructures remain vulnerable to radiation exposure, necessitating close monitoring. In this Review, we provide a comprehensive overview of the consequences of radiation exposure on the cardiovascular system, drawing insights from various cohorts exposed to uniform, whole-body radiation or to partial-body irradiation, and identify potential risk modifiers in the development of radiation-associated cardiovascular disease.

Cardiotoxicity following thoracic radiotherapy for lung cancer

Radiotherapy is the standard of care treatment for unresectable NSCLC, combined with concurrent chemotherapy and adjuvant immunotherapy. Despite technological advances in radiotherapy planning and delivery, the risk of damage to surrounding thoracic tissues remains high. Cardiac problems, including arrhythmia, heart failure and ischaemic events, occur in 20% of patients with lung cancer who undergo radiotherapy. As survival rates improve incrementally for this cohort, minimising the cardiovascular morbidity of RT is increasingly important. Problematically, the reporting of cardiac endpoints has been poor in thoracic radiotherapy clinical trials, and retrospective studies have been limited by the lack of standardisation of nomenclature and endpoints. How baseline cardiovascular profile and cardiac substructure radiation dose distribution impact the risk of cardiotoxicity is incompletely understood. As Thoracic Oncology departments seek to expand the indications for radiotherapy, and as the patient cohort becomes older and more comorbid, there is a pressing need for cardiotoxicity to be comprehensively characterised with sophisticated oncology, physics and cardio-oncology evaluations. This review synthesises the evidence base for cardiotoxicity in conventional radiotherapy, focusing on lung cancer, including current data, unmet clinical needs, and future scientific directions.

Radiation Oncology Opinions and Practice on Cardiotoxicity in Lung Cancer: A Cross-sectional Study by the International Cardio-oncology Society

AIMS

Symptomatic radiation cardiotoxicity affects up to 30% patients with lung cancer and several heart substructure doses are associated with reduced overall survival. A greater focus on minimising cardiotoxicity is now possible due to advancements in radiotherapy technology and the new discipline of cardio-oncology, but uptake of emerging data has not been ascertained. A global cross-sectional analysis of Radiation Oncologists who treat lung cancer was therefore conducted by the International Cardio-Oncology Society in order to establish the impact of recently published literature and guidelines on practice.

MATERIALS AND METHODS

A bespoke questionnaire was designed following an extensive review of the literature and from recurring relevant themes presented at Radiation Oncology and Cardio-Oncology research meetings. Six question domains were retained following consensus discussions among the investigators, comprising 55 multiple choice stems: guidelines, cardiovascular assessment, cardiology investigations, radiotherapy planning strategies, primary prevention prescribing and local cardio-oncology service access. An invitation was sent to all Radiation Oncologists registered with ICOS and to Radiation Oncology colleagues of the investigators.

RESULTS

In total 118 participants were recruited and 92% were consultant physicians. The ICOS 2021 expert consensus statement was rated as the most useful position paper, followed by the joint ESC-ESTRO 2022 guideline. The majority (80%) of participants indicated that a detailed cardiovascular history was advisable. Although 69% of respondents deemed the availability of cardiac substructure auto-segmentation to be very/quite important, it was implemented by only a few, with the most common being the left anterior descending coronary artery V15. A distinct cardio-oncology service was available to 39% participants, while the remainder utilised general cardiology services.

CONCLUSION

The uptake of recent guidelines on cardiovascular optimisation is good, but access to cardiology investigations and consultations, and auto-segmentation, represent barriers to modifying radiotherapy practices in lung cancer to reduce the risk of radiation cardiotoxicity.

A Historical Survey of Key Epidemiological Studies of Ionizing Radiation Exposure

In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis.

Baseline Cardiac Parameters as Biomarkers of Radiation Cardiotoxicity in Lung Cancer: An NI-HEART Analysis

Background

Radiation-induced cardiotoxicity poses a significant challenge in lung cancer management because of the close anatomical proximity of the heart to the lungs, compounded by a high prevalence of cardiovascular risk factors among patients.

Objectives

The aim of this study was to assess the predictive value of routinely available clinical and imaging-based cardiac parameters in identifying "high risk" patients for major adverse cardiac events (MACE) and mortality following radiation therapy (RT).

Methods

The medical records of patients who underwent definitive RT for non-small cell lung cancer using modern planning techniques at a single center between 2015 and 2020 were retrospectively reviewed. Cardiac events were verified by cardiologists, and mortality data were confirmed with the national registry. Cardiac substructures were autosegmented on RT planning scans for retrospective structure and dose analysis, and their correlation with clinical factors was examined. Fine-Gray models were used to analyze relationships while considering the competing risk for death.

Results

Among 478 patients included in the study, 77 (16%) developed 88 MACE, with a median time to event of 16.3 months. A higher burden of pre-existing cardiac diseases was associated with an increased cumulative incidence of MACE (55% [95% CI: 12%-20%] vs 16% [95% CI: 35%-71%]; P < 0.001). Left atrial and left ventricular enlargement on RT planning scans was associated with cumulative incidence of atrial arrhythmia (14% [95% CI: 9%-20%] vs 4% [95% CI: 2%-8%]; P = 0.001) and heart failure (13% [95% CI: 8%-18%] vs 6% [95% CI: 3%-10%]; P = 0.007) at 5 years, respectively. However, myocardial infarction was not associated with the presence of coronary calcium (4.2% [95% CI: 2%-7%] vs 0% [95% CI: 0%-0%]; P = 0.094). No cardiac imaging metrics were found to be both clinically and statistically associated with survival.

Conclusions

The present findings suggest that cardiac history and RT planning scan parameters may offer potential utility in prospectively evaluating cardiotoxicity risk following RT for patients with lung cancer.

Effects of confounding and effect-modifying lifestyle, environmental and medical factors on risk of radiation-associated cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death worldwide. It has been known for some considerable time that radiation is associated with excess risk of CVD. A recent systematic review of radiation and CVD highlighted substantial inter-study heterogeneity in effect, possibly a result of confounding or modifications of radiation effect by non-radiation factors, in particular by the major lifestyle/environmental/medical risk factors and latent period.

METHODS

We assessed effects of confounding by lifestyle/environmental/medical risk factors on radiation-associated CVD and investigated evidence for modifying effects of these variables on CVD radiation dose-response, using data assembled for a recent systematic review.

RESULTS

There are 43 epidemiologic studies which are informative on effects of adjustment for confounding or risk modifying factors on radiation-associated CVD. Of these 22 were studies of groups exposed to substantial doses of medical radiation for therapy or diagnosis. The remaining 21 studies were of groups exposed at much lower levels of dose and/or dose rate. Only four studies suggest substantial effects of adjustment for lifestyle/environmental/medical risk factors on radiation risk of CVD; however, there were also substantial uncertainties in the estimates in all of these studies. There are fewer suggestions of effects that modify the radiation dose response; only two studies, both at lower levels of dose, report the most serious level of modifying effect.

CONCLUSIONS

There are still large uncertainties about confounding factors or lifestyle/environmental/medical variables that may influence radiation-associated CVD, although indications are that there are not many studies in which there are substantial confounding effects of these risk factors.

Pulmonary vein dose and risk of atrial fibrillation in patients with non-small cell lung cancer following definitive radiotherapy: An NI-HEART analysis

BACKGROUND AND PURPOSE

Symptomatic arrhythmia is common following radiotherapy for non-small cell lung cancer (NSCLC), frequently resulting in morbidity and hospitalization. Modern treatment planning technology theoretically allows sparing of cardiac substructures. Atrial fibrillation (AF) comprises the majority of post-radiotherapy arrhythmias, but efforts to prevent this cardiotoxicity have been limited as the causative cardiac substructure is not known. In this study we investigated if incidental radiation dose to the pulmonary veins (PVs) is associated with AF.

MATERIAL AND METHODS

A single-centre study of patients completing contemporary (chemo)radiation for NSCLC, with modern planning techniques. Oncology, cardiology and death records were examined, and AF events were verified by a cardiologist. Cardiac substructures were contoured on planning scans for retrospective dose analysis.

RESULTS

In 420 eligible patients with NSCLC treated with intensity-modulated (70%) or 3D-conformal (30%) radiotherapy with a median OS of 21.8 months (IQR 10.8-35.1), there were 26 cases of new AF (6%). All cases were grade 3 except two cases of grade 4. Dose metrics for both the left (V55) and right (V10) PVs were associated with the incidence of new AF. Metrics remained statistically significant after accounting for the competing risk of death and cardiovascular covariables for both the left (HR 1.02, 95%CI 1.00-1.03, p = 0.005) and right (HR 1.01 (95%CI 1.00-1.02, p = 0.033) PVs.

CONCLUSION

Radiation dose to the PVs during treatment of NSCLC was associated with the onset of AF. Actively sparing the PVs during treatment planning could reduce the incidence of AF during follow-up, and screening for AF may be warranted for select cases.

Potential Role of Global Longitudinal Strain in Cardiac and Oncological Patients Undergoing Cardio-Oncology Rehabilitation (CORE)

Although shown to be effective in improving survival and quality of life in patients with cancer, some treatments are well-known causes of cardiotoxicity, such as anthracyclines, monoclonal antibodies against human epidermal growth factor receptor 2 (HER2) and radiotherapy. To prevent cardiovascular disease (CVD) in patients living with cancer, cardiologists and oncologists promoted the development of cardio-oncology, an interdisciplinary field which aims to further improving life expectancy in these patients. Cardio-oncology rehabilitation (CORE), through correction of risk factors, prescription of drug therapies and structured exercise programs, tries to improve symptoms, quality of life, cardiorespiratory fitness (CRF) and survival in patients with cancer. Different imaging modalities can be used to evaluate the real effectiveness of exercise training on cardiac function. Among these, the global longitudinal strain (GLS) has recently aroused interest, thanks to its high sensitivity and specificity for cardiac dysfunction detection due to advanced ultrasound programs. This review summarizes the evidence on the usefulness of GLS in patients with cancer undergoing cardiac rehabilitation programs.

Global Longitudinal Strain in Cardio-Oncology: A Review

Several therapies used in cancer treatment are potentially cardiotoxic and may cause left ventricular (LV) dysfunction and heart failure. For decades, echocardiography has been the main modality for cardiac assessment in cancer patients, and the parameter examined in the context of cardiotoxicity was the left ventricular ejection fraction (LVEF). The assessment of the global longitudinal strain (GLS) using speckle tracking echocardiography (STE) is an emerging method for detecting and quantifying subtle disturbances in the global long-axis LV systolic function. In the latest ESC guidelines on cardio-oncology, GLS is an important element in diagnosing the cardiotoxicity of oncological therapy. A relative decrease in GLS of >15% during cancer treatment is the recommended cut-off point for suspecting subclinical cardiac dysfunction. An early diagnosis of asymptomatic cardiotoxicity allows the initiation of a cardioprotective treatment and reduces the risk of interruptions or changes in the oncological treatment in the event of LVEF deterioration, which may affect survival.

Cardiotoxicity of Anti-Cancer Radiation Therapy: a Focus on Heart Failure

PURPOSE OF REVIEW

As the percentage of patients achieving long-term survival following treatment of their cancer grows, it is increasingly important to understand the long-term toxicities of cancer-directed treatment. In this review, we highlight the recent findings regarding radiation-induced cardiotoxicity across multiple disease sites, with a particular focus on heart failure.

RECENT FINDINGS

Despite its relative lack of study historically, radiation-induced heart failure has now recently been implicated in several studies of breast cancer, lung cancer, esophageal cancer, and lymphoma as a non-trivial potential consequence of thoracic radiotherapy. Data regarding specific cardiac dosimetric endpoints relevant to cardiotoxicity continue to accumulate. Radiation-induced heart failure is a rare but significant toxicity of thoracic radiotherapy, that is likely underreported. Important areas for future focus include understanding the interplay between thoracic radiotherapy and concurrent cardiotoxic systemic therapy as well as development of potential mitigation strategies and novel therapeutics.

Early GLS changes detection after chemoradiation in locally advanced non-small cell lung cancer (NSCLC)

PURPOSE

Chemoradiation is the standard treatment in patients with locally advanced non-small-cell lung cancer (LA-NSCLC), and thanks to the recent combination with immunotherapy, median survival has unexpectedly improved. This study aims to evaluate early changes in cardiac function after chemoradiotherapy (CRT) in LA-NSCLC by multimodal use of advanced imaging techniques.

MATERIALS AND METHODS

This is a prospective, observational cohort study. At the beginning of combined treatment, screening tests including blood samples, electrocardiogram (ECG), echocardiographic examination (TTE), and cardiac magnetic resonance were performed in all patients with LA-NSCLC. ECG and cardiac marker assays were performed weekly during treatment. ECG and TTE were performed at month 1 (M1) and month 3 (M3) after the end of CRT.

RESULTS

This preliminary analysis included thirty-four patients with a mean age of 69.5 years. The median follow-up was 27.8 months. 62% of patients were in stage IIIA. Radiation therapy was delivered with a median total dose of 60 Gy with conventional fractionation. All patients were treated with concurrent CRT, and 65% of cases were platinum-based therapy. Global longitudinal strain (GLS) and ejection fraction (EF) progressively decreased from baseline to M1 and M3. There was a strong correlation between GLS and EF reduction (at M1: p = 0.034; at M3: p = 0.018). Cardiac arrhythmias occurred in eight patients (23.5%) at a mean follow-up of 15.8 months after CRT.

CONCLUSIONS

Reduction in GLS is an early sign occurring after the end of CRT for LA-NSCLC. Future studies are needed to identify variables that can increase the risk of cardiac events in this patient population to implement adequate damage prevention strategies.

Lack of Cardiotoxicity Endpoints in Prospective Trials Involving Chest Radiation Therapy: A Review of Registered, Latter-Phase Studies

BACKGROUND

Chest radiation therapy (RT) has been associated with increased cardiac morbidity and mortality in numerous studies including the landmark Darby study published in 2013 demonstrating a linear increase in cardiac mortality with increasing mean heart radiation dose. However, the extent to which cardiotoxicity has been incorporated as an endpoint in prospective RT studies remains unknown.

METHODS

We queried clincaltrials.gov to identify phase II/III trials in lung, esophageal, lymphoma, mesothelioma, thymoma, or breast cancer from 1/1/2006-2/1/2021 enrolling greater than 100 patients wherein chest RT was delivered in at least one treatment arm. The primary endpoint was the rate of inclusion of cardiotoxicity as a specific primary or secondary endpoint in the pre- (enrollment started prior to 1/1/2014) versus post-Darby era using the Chi-square test (p<0.05 considered significant). We also analyzed clinical trial factors associated with the inclusion of cardiotoxicity as an endpoint using logistic regression analysis.

RESULTS

In total, 1,822 trials were identified, of which 256 merited inclusion. 32% were for esophageal, 31% lung, 28% breast, and 7% lymphoma/thymoma/mesothelioma cancers, respectively. 5% (N=13) included cardiotoxicity as an endpoint: 6 breast cancer, 3 lung cancer, 3 esophageal cancer, and 1 lymphoma study. There was no difference in the inclusion of cardiotoxicity endpoints in the pre-Darby versus post-Darby era (3.9% vs. 5.9%, P=0.46). The greatest absolute increase in inclusion of cardiotoxicity as an endpoint was seen for lung cancer (0% vs. 6%, p=0.17) and breast cancer (5.7% vs. 10.8%, p=0.43) studies, though these increases remained statistically non-significant. We found no clinical trial factors associated with the inclusion of cardiotoxicity as an endpoint.

CONCLUSIONS

Among prospective trials involving chest RT, cardiotoxicity remains an uncommon endpoint despite its prevalence as a primary source of toxicity following treatment. In order to better characterize cardiac toxicities, future prospective studies involving chest RT should include cardiotoxicity endpoints.

New developments in locally advanced nonsmall cell lung cancer

Locally advanced nonsmall cell lung cancer, due to its varying prognosis, is grouped according to TNM stage IIIA, IIIB and IIIC. Developments over the last 3 years have been focused on the integration of immunotherapy into the combination treatment of a locally definitive therapy (surgery or radiotherapy) and chemotherapy. For concurrent chemoradiotherapy, consolidation therapy with durvalumab was established. Adjuvant targeted therapy has again gained increasing interest. In order to adapt treatment to the specific stage subgroup and its prognosis, fluorodeoxyglucose positron emission tomography/computed tomography and pathological evaluation of the mediastinum are important. Tumours should be investigated for immunological features and driver mutations. Regarding toxicity, evaluation of pulmonary and cardiac function, as well as symptoms and quality of life, is of increasing importance. To improve the management and prognosis of this heterogeneous entity, clinical trials and registries should take these factors into account.

Myocardial deformation after radiotherapy: a layer-specific and territorial longitudinal strain analysis in a cohort of left-sided breast cancer patients (BACCARAT study)

Background

Radiotherapy for breast cancer (BC) and its resulting cardiac exposure are associated with subclinical left ventricular dysfunction characterized by early decrease of global longitudinal strain (LS) measurement based on 2D speckle-tracking echocardiography. Recent software allows multi-layer and segmental analysis of strain, which may be of interest to quantify and locate the impact of cardiac exposure on myocardial function and potentially increase the early detection of radiation-induced cardiotoxicity. The aim of the study was to evaluate whether decrease in LS 6 months after radiotherapy is layer-specific and if it varies according to the left ventricular regional level and the coronary arterial territories.

Methods

LS was measured at baseline before radiotherapy and 6 months post-radiotherapy. The LS was obtained for each myocardial layer (endocardial, mid-myocardial, epicardial), left ventricular regional level (basal, mid, apical) and coronary artery territory (left anterior descending artery (LAD), circumflex artery, right coronary artery).

Results

The study included 64 left-sided BC patients. Mean age was 58 years, mean doses to the heart, the left ventricle and the LAD were respectively 3.0, 6.7 and 16.4 Gy. The absolute decrease of LS was significant for the three layers (endocardial: − 20.0 ± 3.2% to − 18.8 ± 3.8%; mid-myocardial: − 16.0 ± 2.7% to − 15.0 ± 3.1%; epicardial: − 12.3 ± 2.5% to − 11.4 ± 2.8%, all p = 0.02), but only the relative decrease of LS in the endocardial layer was close to be significant (− 4.7%, p = 0.05). More precisely, the LS of the endocardial layer was significantly decreased for the most exposed parts of the left ventricle corresponding to the apical level (− 26.3 ± 6.0% vs. -24.2 ± 7.1%, p = 0.03) and LAD territory (− 22.8 ± 4.0% vs. -21.4 ± 4.8%, p = 0.03).

Conclusion

Six months post-radiotherapy, LS decreased predominantly in the endocardial layer of the most exposed part of the left ventricle. For precise evaluation of radiotherapy-induced cardiotoxicity and early left ventricular dysfunction, the endocardial layer-based LS might be the most sensitive parameter.

Trial registration

ClinicalTrials.gov: NCT02605512, Registered 6 November 2015 - Retrospectively registered.

Early detection of subclinical left ventricular dysfunction after breast cancer radiation therapy using speckle-tracking echocardiography: association between cardiac exposure and longitudinal strain reduction (BACCARAT study)

BACKGROUND

Breast cancer (BC) radiotherapy (RT) can induce cardiotoxicity, with adverse events often observed many years after BC RT. Subclinical left ventricular (LV) dysfunction can be detected early after BC RT with global longitudinal strain (GLS) measurement based on 2D speckle-tracking echocardiography. This 6-month follow-up analysis from the BACCARAT prospective study aimed to investigate the association between cardiac radiation doses and subclinical LV dysfunction based on GLS reduction.

METHODS

The patient study group consisted of 79 BC patients (64 left-sided BC, 15 right-sided BC) treated with RT without chemotherapy. Echocardiographic parameters, including GLS, were measured before RT and 6 months post-RT. The association between subclinical LV dysfunction, defined as GLS reduction > 10%, and radiation doses to whole heart and the LV were performed based on logistic regressions. Non-radiation factors associated with subclinical LV dysfunction including age, BMI, hypertension, hypercholesterolemia and endocrine therapy were considered for multivariate analyses.

RESULTS

A mean decrease of 6% in GLS was observed (- 15.1% ± 3.2% at 6 months vs. - 16.1% ± 2.7% before RT, p = 0.01). For left-sided patients, mean heart and LV doses were 3.1 ± 1.3 Gy and 6.7 ± 3.4 Gy respectively. For right-sided patients, mean heart dose was 0.7 ± 0.5 Gy and median LV dose was 0.1 Gy. Associations between GLS reduction > 10% (37 patients) and mean doses to the heart and the LV as well as the V20 were observed in univariate analysis (Odds Ratio = 1.37[1.01-1.86], p = 0.04 for Dmean Heart; OR = 1.14 [1.01-1.28], p = 0.03 for Dmean LV; OR = 1.08 [1.01-1.14], p = 0.02 for LV V20). In multivariate analysis, these associations did not remain significant after adjustment for non-radiation factors. Further exploratory analysis allowed identifying a subgroup of patients (LV V20 > 15%) for whom a significant association with subclinical LV dysfunction was found (adjusted OR = 3.97 [1.01-15.70], p = 0.048).

CONCLUSIONS

This analysis indicated that subclinical LV dysfunction defined as a GLS decrease > 10% is associated with cardiac doses, but adjustment for non-radiation factors such as endocrine therapy lead to no longer statistically significant relationships. However, LV dosimetry may be promising to identify high-risk subpopulations. Larger and longer follow-up studies are required to further investigate these associations.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02605512, Registered 6 November 2015 - Retrospectively registered.