Persistent Impairment in Cardiopulmonary Fitness after Breast Cancer Chemotherapy

Relevance of Cardiovascular Exercise in Cancer and Cancer Therapy-Related Cardiac Dysfunction

PURPOSE OF THE REVIEW

Cancer therapy-related cardiac dysfunction (CTRCD) has been identified as a threat to overall and cancer-related survival. Although aerobic exercise training (AET) has been shown to improve cardiorespiratory fitness (CRF), the relationship between specific exercise regimens and cancer survival, heart failure development, and reduction of CTRCD is unclear. In this review, we discuss the impact of AET on molecular pathways and the current literature of sports in the field of cardio-oncology.

RECENT FINDINGS

Cardio-oncological exercise trials have focused on variations of AET intensity by using moderate continuous and high intensity interval training, which are applicable, safe, and effective approaches to improve CRF. AET increases CRF, reduces cardiovascular morbidity and heart failure hospitalization and should thus be implemented as an adjunct to standard cancer therapy, although its long-term effect on CTRCD remains unknown. Despite modulating diverse molecular pathways, it remains unknown which exercise regimen, including variations of AET duration and frequency, is most suited to facilitate peripheral and central adaptations to exercise and improve survival in cancer patients.

Protective effects of exercise on cardiotoxicity induced by breast cancer treatments: A systematic review and meta-analysis

OBJECTIVE

Currently, one of the main causes of death in women with breast cancer is cardiovascular disease caused by the oncologic therapies. Exercise has demonstrated positive effects on cardiovascular fitness in individuals without cancer. Therefore, the aim of this study was to evaluate the cardioprotective effects of exercise in women with breast cancer, during and after the application of their treatments.

METHODS

Systematic search was done in PubMed, Scopus, Web of Science, CINAHL, MEDLINE, SPORTDiscus, and PEDro. The articles must have been published in the last ten years; the intervention to be evaluated was to consist of an exercise program; the sample had to comprise women who were undergoing breast cancer treatment or who had completed it at the time of the intervention; and the outcome variables had to include at least one parameter for the assessment of cardiac function and/or structure.

RESULTS

Of the 28 articles identified, nine reported non-randomized controlled studies, 16 randomized clinical trials and three quasi-experimental studies. The effects of exercise on left ventricular ejection fraction, global longitudinal strain and the E/A waveforms ratio were not significant. However, its effect on VO2max was significant.

CONCLUSIONS

Exercise does not seem to be effective in avoiding the cardiotoxic effects of oncological treatment for breast cancer. Although exercise seems to mitigate the symptomatology, reflected in improved functional capacity, more long-term studies are needed.

PROSPERO REGISTRATION CODE

CRD42023391441.

Digital home-based post-treatment exercise interventions for female cancer survivors: A systematic review and meta-analysis

BACKGROUND

Although exercise benefits female cancer survivors, clinical decision-making regarding timing, frequency, duration, and intensity is lacking. Optimizing exercise interventions in this population is necessary. This study aimed to describe existing digital home-based exercises and to assess their effectiveness at improving physical health in female cancer survivors upon completion of therapy.

DESIGN

We conducted a systematic review using articles from Web of Science, Embase and Medline (Ovid). We included intervention studies examining the effects of digital home-based exercise programs on post-treatment recovery in female cancer survivors. Rob2 and ROBIN I were used to assess quality of studies. Quality-of-life, fatigue score, and physical performance were assessed using meta-analysis.

RESULTS

This study involved 1578 female cancer survivors in 21 interventions. Following guidelines and supervised exercise with coaches led to better outcomes than interventions without guidelines, programs without coaches, or lower intensity exercise. Exercise led to significant improvement in some physical performance outcomes. Significant improvements were seen in physical performance outcomes, including the 6-min walk test, metabolic equivalent task, and number of steps per day.

CONCLUSION

Providing cancer survivors with standard guidelines for home-based, coach-supervised, vigorous exercise on digital platforms could improve their physical function, health, and quality-of-life.

Effects of aerobic combined with resistance exercise on cardiorespiratory fitness and cardiometabolic health in breast cancer survivors: A Systematic Review, meta-analysis and meta-regression

Background

Cardiotoxicity from chemotherapy is a serious risk to the quality of survival of breast cancer survivors (BCS), and aerobic combined with resistance exercise (CE) has the potential to combat this cardiac damage. However, there is a lack of high-quality studies to assess the specific effects of CE. This study aimed to investigate the effects of CE on cardiopulmonary function (CRF) and cardiometabolic health in BCS.

Methods

A comprehensively searched of the 4 databases (PubMed, Embase, Web of Science, Cochrane Library) from the database construction until March 1, 2023. The included studies were randomized controlled trials (RCTs) reporting the effects of CE on CRF and cardiometabolic health in BCS. The quality of the literature was assessed by two independent reviewers using the Cochrane Collaboration Risk of Bias Tool. Weight means difference (WMD), or standardized mean difference (SMD), were combined using random or fixed effects models. Subgroup and meta-regression explored heterogeneity as well as covariate effects.

Results

40 studies were included in the meta-analysis, with 2849 participants. Results showed that CE significantly increased maximal oxygen uptake (VO2max) (WMD:4.55; 95% CI:2.84, 6.26; I2 = 91.90%, P < 0.001) and reduced body weight (BW) (WMD: 1.61; 95% CI: 2.44, -0.78; I2 = 38.60%, P = 0.032) and body mass index (BMI) (WMD: 0.86; 95% CI: 1.43, -0.29; I2 = 70.50%, P < 0.001) in BCS. Subgroup analysis showed that BMI (WMD: 1.15; 95% CI: 1.89, -0.41; I2 = 76.90%, P < 0.001) and VO2max (WMD:4.21; 95% CI:2.40, 6.02; I2 = 96.4%, P < 0.001) were more effective with supervision. Meta-regression analysis showed that sample size had a significant moderating effect on BW (Coeff: 0.03, 95% CI: 0.00, 0.06).

Conclusions

CE significantly increases CRF in BCS and improves most cardiometabolic health-related outcomes. In addition, there will be a need for many larger RCTs to explore the effects of CE on inflammatory biomarkers in BCS.

Exercise, cancer, and the cardiovascular system: clinical effects and mechanistic insights

Cardiovascular diseases and cancer are the leading causes of death in the Western world and share common risk factors. Reduced cardiorespiratory fitness (CRF) is a major determinant of cardiovascular morbidity and cancer survival. In this review we discuss cancer- induced disturbances of parenchymal, cellular, and mitochondrial function, which limit CRF and may be antagonized and attenuated through exercise training. We show the impact of CRF on cancer survival and its attenuating effects on cardiotoxicity of cancer-related treatment. Tailored exercise programs are not yet available for each tumor entity as several trials were performed in heterogeneous populations without adequate cardiopulmonary exercise testing (CPET) prior to exercise prescription and with a wide variation of exercise modalities. There is emerging evidence that exercise may be a crucial pillar in cancer treatment and a tool to mitigate cardiotoxic treatment effects. We discuss modalities of aerobic exercise and resistance training and their potential to improve CRF in cancer patients and provide an example of a periodization model for exercise training in cancer.

Determinants of Impaired Peak Oxygen Uptake in Breast Cancer Survivors: JACC: CardioOncology Primer

•Exercise intolerance is common among breast cancer survivors.•Exercise intolerance in breast cancer survivors is related to cardiac, vascular, and skeletal muscle impairments.•Holistic rehabilitation or pharmacological therapies are needed to address these impairments.

A Review on the Role of Exercise Training to Prevent a Decline in Cardiorespiratory Fitness and Cardiac Function in Breast Cancer Survivors

PURPOSE

Improvements in diagnosis and treatment mean that the long-term health of breast cancer survivors (BCS) is increasingly dictated by cardiovascular comorbidities. This is partly a consequence of exposure to cardiotoxic therapies, which result in cardiac dysfunction and decreased cardiorespiratory fitness (CRF). Exercise training (ExT) is a key therapeutic strategy for secondary prevention and increasing CRF in adults with established cardiovascular disease. Exercise-based cardio-oncology rehabilitation (CORE) has been proposed as an emerging strategy to address CRF and cardiac impairment in BCS. This review aims to (1) provide an overview of the impact of breast cancer therapy on CRF; (2) provide an up-to-date summary of the effects of ExT on CRF and cardiac function in BCS undergoing cardiotoxic therapy; and (3) discuss how traditional ExT approaches can be adapted for BCS undergoing therapy.

REVIEW METHODS

A literature review was performed based on an intensive literature search for systematic reviews and meta-analyses, randomized and non-randomized controlled trials and single-arm trials investigating the impact of exercise training or cardiac rehabilitation on CRF and/or cardiac function in BCS who are undergoing or have completed cardiotoxic cancer therapy.

SUMMARY

Overall, current evidence suggests that ExT induces clinically meaningful benefits for CRF in BCS during and after therapy. There is also emerging evidence that ExT can improve peak exercise measures of cardiac function; however, there is a need for further research to understand how to adapt these effective ExT approaches into clinical CORE-based settings.

Timing of exercise therapy when initiating adjuvant chemotherapy for breast cancer: a randomized trial

AIMS

The most appropriate timing of exercise therapy to improve cardiorespiratory fitness (CRF) among patients initiating chemotherapy is not known. The effects of exercise therapy administered during, following, or during and following chemotherapy were examined in patients with breast cancer.

METHODS AND RESULTS

Using a parallel-group randomized trial design, 158 inactive women with breast cancer initiating (neo)adjuvant chemotherapy were allocated to receive (1:1 ratio): usual care or one of three exercise regimens-concurrent (during chemotherapy only), sequential (after chemotherapy only), or concurrent and sequential (continuous) (n = 39/40 per group). Exercise consisted of treadmill walking three sessions/week, 20-50 min at 55%-100% of peak oxygen consumption (VO2peak) for ≈16 (concurrent, sequential) or ≈32 (continuous) consecutive weeks. VO2peak was evaluated at baseline (pre-treatment), immediately post-chemotherapy, and ≈16 weeks after chemotherapy. In intention-to-treat analysis, there was no difference in the primary endpoint of VO2peak change between concurrent exercise and usual care during chemotherapy vs. VO2peak change between sequential exercise and usual care after chemotherapy [overall difference, -0.88 mL O2·kg-1·min-1; 95% confidence interval (CI): -3.36, 1.59, P = 0.48]. In secondary analysis, continuous exercise, approximately equal to twice the length of the other regimens, was well-tolerated and the only strategy associated with significant improvements in VO2peak from baseline to post-intervention (1.74 mL O2·kg-1·min-1, P < 0.001).

CONCLUSION

There was no statistical difference in CRF improvement between concurrent vs. sequential exercise therapy relative to usual care in women with primary breast cancer. The promising tolerability and CRF benefit of ≈32 weeks of continuous exercise therapy warrant further evaluation in larger trials.

Cardiac and intramuscular adaptations following short-term exercise prehabilitation in unfit patients scheduled to undergo hepatic or pancreatic surgery: study protocol of a multinuclear MRI study

INTRODUCTION

Short-term exercise prehabilitation programmes have demonstrated promising results in improving aerobic capacity of unfit patients prior to major abdominal surgery. However, little is known about the cardiac and skeletal muscle adaptations explaining the improvement in aerobic capacity following short-term exercise prehabilitation.

METHODS AND ANALYSIS

In this single-centre study with a pretest-post-test design, 12 unfit patients with a preoperative oxygen uptake (VO2) at the ventilatory anaerobic threshold ≤13 mL/kg/min and/or VO2 at peak exercise ≤18 mL/kg/min, who are scheduled to undergo hepatopancreatobiliary surgery at the University Medical Center Groningen (UMCG), the Netherlands, will be recruited. As part of standard care, unfit patients are advised to participate in a home-based exercise prehabilitation programme, comprising high-intensity interval training and functional exercises three times per week, combined with nutritional support, during a 4-week period. Pre-intervention and post-intervention, patients will complete a cardiopulmonary exercise test. Next to this, study participants will perform additional in-vivo exercise cardiac magnetic resonance (MR) imaging and phosphorus 31-MR spectroscopy of the quadriceps femoris muscle before and after the intervention to assess the effect on respectively cardiac and skeletal muscle function.

ETHICS AND DISSEMINATION

This study was approved in May 2023 by the Medical Research Ethics Committee of the UMCG (registration number NL83611.042.23, March 2023) and is registered in the ClinicalTrials.gov register. Results of this study will be submitted for presentation at (inter)national congresses and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05772819.

Anti-breast cancer-induced cardiomyopathy: Mechanisms and future directions

With the progression of tumor treatment, the 5-year survival rate of breast cancer is close to 90%. Cardiovascular toxicity caused by chemotherapy has become a vital factor affecting the survival of patients with breast cancer. Anthracyclines, such as doxorubicin, are still some of the most effective chemotherapeutic agents, but their resulting cardiotoxicity is generally considered to be progressive and irreversible. In addition to anthracyclines, platinum- and alkyl-based antitumor drugs also demonstrate certain cardiotoxic effects. Targeted drugs have always been considered a relatively safe option. However, in recent years, some random clinical trials have observed the occurrence of subclinical cardiotoxicity in targeted antitumor drug users, which may be related to the effects of targeted drugs on the angiotensin converting enzyme, angiotensin receptor and β receptor. The use of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and beta-blockers may prevent clinical cardiotoxicity. This article reviews the toxicity and mechanisms of current clinical anti-breast cancer drugs and proposes strategies for preventing cardiovascular toxicity to provide recommendations for the clinical prevention and treatment of chemotherapy-related cardiomyopathy.

Incorporating Exercise Training into Cardio-Oncology Care: Current Evidence and Opportunities: JACC: CardioOncology State-of-the-Art Review

Cancer treatment-induced cardiotoxicities are an ongoing concern throughout the cancer care continuum from treatment initiation to survivorship. Several "standard-of-care" primary, secondary, and tertiary prevention strategies are available to prevent the development or further progression of cancer treatment-induced cardiotoxicities and their risk factors. Despite exercise's established benefits on the cardiovascular system, it has not been widely adopted as a nonpharmacologic cardioprotective strategy within cardio-oncology care. In this state-of-the-art review, the authors discuss cancer treatment-induced cardiotoxicities, review the existing evidence supporting the role of exercise in preventing and managing these sequelae in at-risk and affected individuals living after cancer diagnoses, and propose considerations for implementing exercise-based services in cardio-oncology practice.

Effect of home-based online training and activity feedback on oxygen uptake in patients after surgical cancer therapy: a randomized controlled trial

BACKGROUND

Exercise training is beneficial in enhancing physical function and quality of life in cancer patients. Its comprehensive implementation remains challenging, and underlying cardiopulmonary adaptations are poorly investigated. This randomized controlled trial examines the implementation and effects of home-based online training on cardiopulmonary variables and physical activity.

METHODS

Of screened post-surgical patients with breast, prostate, or colorectal cancer, 148 were randomly assigned (1:1) to an intervention (2 × 30 min/week of strength-endurance training using video presentations) and a control group. All patients received activity feedback during the 6-month intervention period. Primary endpoint was change in oxygen uptake after 6 months. Secondary endpoints included changes in cardiac output, rate pressure product, quality of life (EORTC QoL-C30), C-reactive protein, and activity behavior.

RESULTS

One hundred twenty-two patients (62 intervention and 60 control group) completed the study period. Change in oxygen uptake between intervention and control patients was 1.8 vs. 0.66 ml/kg/min (estimated difference after 6 months: 1.24; 95% CI 0.23 to 2.55; p = 0.017). Rate pressure product was reduced in IG (estimated difference after 6 months: - 1079; 95% CI - 2157 to - 1; p = 0.05). Physical activity per week was not different in IG and CG. There were no significant interaction effects in body composition, cardiac output, C-reactive protein, or quality of life.

CONCLUSIONS

Home-based online training among post-surgery cancer patients revealed an increase of oxygen uptake and a decrease of myocardial workload during exercise. The implementation of area-wide home-based training and activity feedback as an integral component in cancer care and studies investigating long-term effects are needed.

TRIAL REGISTRATION

DRKS-ID: DRKS00020499 ; Registered 17 March 2020.

Effects of exercise training on cardiac toxicity markers in women with breast cancer undergoing chemotherapy with anthracyclines: a randomized controlled trial

AIMS

Exercise training has been suggested to prevent anthracycline-related cardiac dysfunction, but clinicalbased evidence is scarce. We investigated the effects of a supervised exercise training programme (SETP) on cardiac toxicity markers in women with breast cancer (BC) receiving anthracycline-containing chemotherapy.

METHODS AND RESULTS

Ninety-three women with early-stage breast cancer were randomly allocated to a supervised exercise training programme (SETP) plus usual care group (Exercise, n = 47) or usual care alone group (UC, n = 46). The SETP consisted of three sessions per week, combining aerobic and resistance training, conducted concurrently across the anthracycline-containing chemotherapy length. The primary endpoint was the change in left ventricular ejection fraction (LVEF) from baseline to the end of anthracycline cycles. Secondary endpoints included global longitudinal strain (GLS) and other conventional echocardiographic parameters, cardiorespiratory fitness (estimated peak VO2), circulating biomarkers (NT-proBNP, hs-TnT), and safety of the SETP. The study endpoints were also assessed 3 months after the end of anthracycline cycles. All patients were prescribed four cycles of doxorubicin plus cyclophosphamide (AC). No significant between-group differences in LVEF change were seen at the end of AC [mean difference: 0.7%; 95% confidence interval (CI): -0.8, 2.3; P = 0.349] and 3 months after AC (1.1%; 95% CI: -0.5, 2.6; P = 0.196). Compared to the usual care (UC) group, the estimated peak VO2 increased in the Exercise group at the end of AC (1.6 mL O2·kg-1·min-1; 95% CI: 0.06, 3.1; P = 0.041) and 3 months after AC (3.1 mL O2·kg-1·min-1; 95% CI: 1.4, 4.7; P < 0.001). No between-group differences were found in the remaining secondary endpoints. No serious adverse events were observed during SETP.

CONCLUSION

Exercise training was safe during chemotherapy and significantly improved cardiorespiratory fitness. No significant effects were seen on cardiac toxicity markers (LVEF or GLS) as compared to the usual care.

TRIAL REGISTRATION

Mama Move Gaia on treatment trial ISRCTN32617901.

Feasibility of Aerobic Exercise Training to Mitigate Cardiotoxicity of Breast Cancer Therapy: A Systematic Review and Meta-Analysis

BACKGROUND

Current anticancer treatments for breast cancer (BC) may cause cardiotoxicity. This study aimed to investigate the effectiveness of aerobic exercise in mitigating cardiotoxicity caused by BC therapy.

MATERIALS AND METHODS

PubMed, Embase, Cochrane Library, Web of Science, and the Physiotherapy Evidence Database were searched until February 7, 2023. Clinical trials investigating the effectiveness of exercise training, including aerobic exercise, in BC patients receiving treatments that could cause cardiotoxicity were eligible. Outcome measures included cardiorespiratory fitness (CRF) (peak oxygen consumption, VO₂peak), left ventricular ejection fraction, and peak oxygen pulse. Intergroup differences were determined by standard mean differences (SMD) and 95% confidence intervals (CIs). Trial sequential analysis (TSA) was utilized to ensure whether the current evidence was conclusive.

RESULTS

Sixteen trials involving 876 participants were included. Aerobic exercise significantly improved CRF measured by VO₂peak in mL/kg/min (SMD 1.79, 95% CI 0.99-2.59) when compared to usual care. This result was confirmed through TSA. Subgroup analyses revealed that aerobic exercise given during BC therapy significantly improved VO₂peak (SMD 1.84, 95% CI 0.74-2.94). Exercise prescriptions at a frequency of up to 3 times per week, an intensity of moderate to vigorous, and a >30-minute session length also improved VO₂peak.

CONCLUSION

Aerobic exercise is effective in improving CRF when compared to usual care. Exercise performed up to 3 times per week, at a moderate-to-vigorous intensity, and having a session length >30 minutes is considered effective. Future high-quality research is needed to determine the effectiveness of exercise intervention in preventing cardiotoxicity caused by BC therapy.

High-intensity exercise prescription guided by heart rate variability in breast cancer patients: a study protocol for a randomized controlled trial

BACKGROUND

Breast cancer is a chronic disease with a large growth in its treatments, prognosis, improvements, side effects and rehabilitation therapies research. These advances have also highlighted the need to use physical exercise as a countermeasure to reduce the cardiotoxicity of pharmacological treatments, increase patients' strength and quality of life and improve body composition, physical condition and mental health. However, new investigations show the need for a closed exercise individualisation to produce higher physiological, physical and psychological benefits in remote exercise programs. To this end, the present study will use, in a novel way in this population, heart rate variability (HRV) as a measure for prescribing high-intensity training. Thus, the primary objective of this randomised clinical trial is to analyse the effects of a high-intensity exercise program daily guided by HRV, a preplanned moderate to high-intensity exercise intervention and a usual care group, in breast cancer patients after chemotherapy and radiotherapy treatments.

METHODS

For this purpose, a 16-week intervention will be carried out with 90 breast cancer patients distributed in 3 groups (a control group, a moderate to high-intensity preplanned exercise group and a high-intensity exercise group guided by HRV). Both physical exercise interventions will be developed remotely and supervised including strength and cardiovascular exercises. Physiological variables, such as cardiotoxicity, biomarkers, lipid profile, glucose, heart rate and blood pressure; physical measures like cardiorespiratory capacity, strength, flexibility, agility, balance and body composition; and psychosocial variables, as health-related quality of life, fatigue, functionality, self-esteem, movement fear, physical exercise level, anxiety and depression will be measure before, after the intervention and 3 and 6 months follow up.

DISCUSSION

Personalized high-intensity exercise could be a promising exercise intervention in contrast to moderate-intensity or usual care in breast cancer patients to reach higher clinical, physical and mental effects. In addition, the novelty of controlling HRV measures daily may reflect exercise effects and patients' adaptation in the preplanned exercise group and a new opportunity to adjust intensity. Moreover, findings may support the effectiveness and security of physical exercise remotely supervised, although with high-intensity exercise, to reach cardiotoxicity improvements and increase physical and psychosocial variables after breast cancer treatments. Trial registration ClinicalTrials.gov nº NCT05040867 ( https://clinicaltrials.gov/ct2/show/record/NCT05040867 ).

Exercise for the Prevention of Anthracycline-Induced Functional Disability and Cardiac Dysfunction: The BREXIT Study

BACKGROUND

Breast cancer survivors treated with anthracycline-based chemotherapy (AC) have increased risk of functional limitation and cardiac dysfunction. We conducted a 12-month randomized controlled trial in 104 patients with early-stage breast cancer scheduled for AC to determine whether 12 months of exercise training (ExT) could attenuate functional disability (primary end point), improve cardiorespiratory fitness (VO₂peak), and prevent cardiac dysfunction.

METHODS

Women 40 to 75 years of age with stage I to III breast cancer scheduled for AC were randomized to 3 to 4 days per week aerobic and resistance ExT for 12 months (n=52) or usual care (UC; n=52). Functional measures were performed at baseline, at 4 weeks after AC (4 months), and at 12 months, comprising: (1) cardiopulmonary exercise testing to quantify VO₂peak and functional disability (VO₂peak ≤18.0 mL·kg^-1·min^-1); (2) cardiac reserve (response from rest to peak exercise), quantified with exercise cardiac magnetic resonance measures to determine changes in left and right ventricular ejection fraction, cardiac output, and stroke volume; (3) standard-of-care echocardiography-derived resting left ventricular ejection fraction and global longitudinal strain; and (4) biochemistry (troponin and BNP [B-type natriuretic peptide]).

RESULTS

Among 104 participants randomized, greater study attrition was observed among UC participants (P=0.031), with 93 women assessed at 4 months (ExT, n=49; UC, n=44) and 87 women assessed at 12 months (ExT, n=49; UC, n=38). ExT attenuated functional disability at 4 months (odds ratio, 0.32 [95% CI, 0.11-0.94]; P=0.03) but not at 12 months (odds ratio, 0.27 [95% CI, 0.06-1.12]; P=0.07). In a per-protocol analysis, functional disability was prevented entirely at 12 months among participants adherent to ExT (ExT, 0% versus UC, 20%; P=0.005). Compared with UC at 12 months, ExT was associated with a net 3.5-mL·kg^-1·min^-1 improvement in VO₂peak that coincided with greater cardiac output, stroke volume, and left and right ventricular ejection fraction reserve (P<0.001 for all). There was no effect of ExT on resting measures of left ventricular function. Postchemotherapy troponin increased less in ExT than in UC (8-fold versus 16-fold increase; P=0.002). There were no changes in BNP in either group.

CONCLUSIONS

In women with early-stage breast cancer undergoing AC, 12 months of ExT did not attenuate functional disability, but provided large, clinically meaningful benefits on VO₂peak and cardiac reserve.

REGISTRATION

URL: https://www.anzctr.org.au/; Unique identifier: ACTRN12617001408370.

Cardiotoxicity from neoadjuvant targeted treatment for breast cancer prior to surgery

Cancer treatment has been gradually shifting from non-specific cytotoxic agents to molecularly targeted drugs. Breast cancer (BC), a malignant tumor with one of the highest incidence worldwide, has seen a rapid development in terms of targeted therapies, leading to a radical change in the treatment paradigm. However, the use of targeted drugs is accompanied by an increasing rate of deaths due to non-tumor-related causes in BC patients, with cardiovascular complications as the most common cause. Cardiovascular toxicity during antitumor therapy has become a high-risk factor for survival in BC patients. Targeted drug-induced cardiotoxicity exerts a wide range of effects on cardiac structure and function, including conduction disturbances, QT interval prolongation, impaired myocardial contractility, myocardial fibrosis, and hypertrophy, resulting in various clinical manifestations, e.g., arrhythmias, cardiomyopathy, heart failure, and even sudden death. In adult patients, the incidence of antitumor targeted drug-induced cardiotoxicity can reach 50%, and current preclinical evaluation tools are often insufficiently effective in predicting clinical cardiotoxicity. Herein, we reviewed the current status of the occurrence, causative mechanisms, monitoring methods, and progress in the prevention and treatment of cardiotoxicity associated with preoperative neoadjuvant targeted therapy for BC. It supplements the absence of relevant review on the latest research progress of preoperative neoadjuvant targeted therapy for cardiotoxicity, with a view to providing more reference for clinical treatment of BC patients.

Feasibility, Safety, and Preliminary Efficacy of Very Low-Volume Interval Training in Advanced Cancer Patients

PURPOSE

High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness (CRF) and health-related outcomes in various chronic diseases, including cancer. However, data on feasibility and efficacy of HIIT in advanced cancer patients are still sparse, presumably because of safety concerns, like suspected immunosuppression after vigorous exercise. This randomized, sham-intervention controlled study aimed to investigate feasibility, safety, and preliminary efficacy of very low-volume HIIT (LOW-HIIT) in advanced cancer patients.

METHODS

Twenty-seven patients (55.4 ± 13.2 yr) with different advanced cancers (Union for International Cancer Control [UICC] III/IV) were randomly allocated to LOW-HIIT ( n = 13), consisting of 5 × 1 min cycle ergometer intervals (14 min per session total duration) at 80% to 95% HR peak (two sessions per week for 12 wk), or a sham intervention ( n = 14) performing light physical mobilization exercises (SHAM). Primary outcomes were attrition and attendance rates, with values of ≤25% and ≥80%, respectively, considered acceptable. Secondary outcomes were safety, protocol fidelity, physiological (including CRF measures) and patient-reported outcomes (including fatigue and quality of life).

RESULTS

One of 13 patients (8%) receiving LOW-HIIT dropped out. Mean attendance rate was ~93%. The prescribed minimum exercise intensity was consistently reached by all patients. Low-volume HIIT was well tolerated and not associated with any serious adverse event nor with increased infection susceptibility. There were no biochemical signs of acute immunosuppression after LOW-HIIT. Contrarily, differentiation and degranulation of natural killer cells was acutely increased postexercise. Low-volume HIIT improved CRF measures including peak oxygen uptake, self-reported fatigue, physical, and social functioning. No significant changes occurred in the SHAM group.

CONCLUSIONS

Low-volume HIIT can be regarded as feasible and safe in advanced cancer patients. Our preliminary data indicate favorable acute effects on NK-cells and beneficial chronic adaptations in CRF, fatigue, and aspects of quality of life.

Cardiotoxicity is mitigated after a supervised exercise program in HER2-positive breast cancer undergoing adjuvant trastuzumab

Background

Trastuzumab is used, alone or in conjunction with standard chemotherapy, to treat HER2-positive breast cancer (BC). Although it improves cancer outcomes, trastuzumab. can lead to cardiotoxicity. Physical exercise is a safe and effective supportive therapy in the management of side effects, but the cardioprotective effects of exercise are still unclear.

Objectives

The primary aim of this study was to test whether trastuzumab-induced cardiotoxicity [left ventricular ejection fraction (LVEF) under 50%, or an absolute drop in LVEF of 10%] was reduced after a supervised exercise program of 3 months in patients with HER2-positive breast cancer. Secondary endpoints were to evaluate (i) cardiotoxicity rates using other criteria, (ii) cardiac parameters, (iii) cardiorespiratory fitness and (iv) whether a change in LVEF influences the cardiorespiratory fitness.

Methods

89 women were randomized to receive adjuvant trastuzumab in combination with a training program (training group: TG; n = 46) or trastuzumab alone (control group: CG; n = 43). The primary and secondary endpoints were evaluated at the end of the supervised exercise program of 3 months (T3).

Results

After exercise program, 90.5 % of TG patients and 81.8% of CG patients did not exhibit cardiotoxicity. Furthermore, whatever the used criterion, percentage of patients without cardiotoxicity were greater in TG (97.6 and 100% respectively) than in CG (90.9 and 93.9% respectively). LVEF and GLS values remained stable in both groups without any difference between the groups. In contrast, at T3, peak VO2 (+2.6 mL.min−1.kg−1; 95%CI, 1.8 to 3.4) and maximal power (+21.3 W; 95%CI, 17.3 to 25.3) increased significantly in TG, whereas they were unchanged in CG (peak VO2: +0.2 mL.min−1.kg−1; 95%CI, −0.5 to 0.9 and maximal power: +0.7 W, 95%CI, −3.6 to 5.1) compared to values measured at T0. No correlation between LVEF changes and peak VO2 or maximal power was observed.

Conclusion

A 12-week supervised exercise regimen was safe and improved the cardiopulmonary fitness in particular peak VO2, in HER2-positive BC patients treated with adjuvant trastuzumab therapy. The study is under powered to come to any conclusion regarding the effect on cardiotoxicity.

Clinical trial registration

www.ClinicalTrials.gov, identifier: NCT02433067.

Cardiovascular Dysautonomia in Patients with Breast Cancer

Breast cancer is the most frequent malignant disease among women, being responsible for a considerable percentage of fatalities and comorbidities every year. Despite advances in early detection and therapy, evidence shows that breast cancer survivors are at increased risk of developing other chronic conditions, such as cardiovascular diseases.

Autonomic dysfunction is an emerging, but poorly understood topic that has been suggested as a risk factor for cardiovascular disease in breast cancer patients. It clinically manifests through persistently elevated heart rates and abnormal heart rate variability, even before any signs of cardiovascular dysfunction appear. Since changes in the left ventricular ejection fraction only manifest when myocardial injury has already occurred, it has been hypothesized that autonomic dysfunction can constitute an early biomarker of cardiovascular impairment in breast cancer patients.

This review focuses on the direct and indirect effects of cancer and its treatment on the autonomic nervous system in breast cancer patients. We highlight the mechanisms potentially involved in cancer and antineoplastic therapy-related autonomic imbalance and review the potential strategies to prevent and/or attenuate autonomic dysfunction.

There are gaps in the current knowledge; more research in this area is needed to identify the relevance of autonomic dysfunction and define beneficial interventions to prevent cardiovascular disease in breast cancer patients.

Breast cancer survivors with preserved or rescued cardiorespiratory fitness have similar cardiac, pulmonary and muscle function compared to controls

Breast cancer survivors (BCS) have a high prevalence of cardiovascular disease and low cardiorespiratory fitness (CRF). CRF is an important predictor of survival in BCS. However, the physiological factors that contribute to low CRF in BCS have not been completely elucidated. To assess differences in physiological factors (cardiac, pulmonary, muscle function) related to CRF between BCS and controls. Twenty-three BCS and 23 age-body mass index (BMI) matched controls underwent a peak cycling exercise test to determine CRF, with physiological factors measured at resting and at peak exercise. Cardiac hemodynamics (stroke volume [SV], SVindex, heart rate [HR], cardiac output [Formula: see text], and [Formula: see text]index) were evaluated using ultrasonography. Pulmonary function was evaluated using the oxygen uptake efficiency slope (OUES), ventilation to carbon dioxide production slope [Formula: see text] and breathing reserve at peak exercise (BR). Muscle oxygenation variables (oxygenated [HbO₂] deoxygenated [HHb] and total hemoglobin [Hb], and tissue oxygenation index [TSI]) were measured with near-infrared spectroscopy (NIRS). Both groups had similar CRF and similarly increased all hemodynamic variables (HR, SV, SVindex, [Formula: see text] and [Formula: see text]index) at peak exercise compared to resting (p < 0.001). BCS had higher overall HR and lower SVindex (group effect, p < 0.05). BCS had similar OUES, [Formula: see text] and BR compared to the controls. Both groups decreased TSI, and increased Hb and HHb similarly at peak exercise compared to resting (p < 0.001). Our data suggest BCS do not exhibit differences in cardiac, pulmonary, or muscle function at peak exercise compared to controls, when both groups have similar CRF and physical activity.

Novel Therapeutics for Anthracycline Induced Cardiotoxicity

Anthracyclines remain an essential component of the treatment of many hematologic and solid organ malignancies, but has important implications on cardiovascular disease. Anthracycline induced cardiotoxicity (AIC) ranges from asymptomatic LV dysfunction to highly morbid end- stage heart failure. As cancer survivorship improves, the detection and treatment of AIC becomes more crucial to improve patient outcomes. Current treatment modalities for AIC have been largely extrapolated from treatment of conventional heart failure, but developing effective therapies specific to AIC is an area of growing research interest. This review summarizes the current evidence behind the use of neurohormonal agents, dexrazoxane, and resynchronization therapy in AIC, evaluates the clinical outcomes of advanced therapy and heart transplantation in AIC, and explores future horizons for treatment utilizing gene therapy, stem cell therapy, and mechanism-specific targets.

Exercise Cardio-Oncology: Exercise as a Potential Therapeutic Modality in the Management of Anthracycline-Induced Cardiotoxicity

Anthracyclines are one of the most effective chemotherapy agents and have revolutionized cancer therapy. However, anthracyclines can induce cardiac injuries through ‘multiple-hits', a series of cardiovascular insults coupled with lifestyle risk factors, which increase the risk of developing short- and long-term cardiac dysfunction and cardiovascular disease that potentially lead to premature mortality following cancer remission. Therefore, the management of anthracycline-induced cardiotoxicity is a serious unmet clinical need. Exercise therapy, as a non-pharmacological intervention, stimulates numerous biochemical and physiologic adaptations, including cardioprotective effects, through the cardiovascular system and cardiac muscles, where exercise has been proposed to be an effective clinical approach that can protect or reverse the cardiotoxicity from anthracyclines. Many preclinical and clinical trials demonstrate the potential impacts of exercise on cardiotoxicity; however, the underlying mechanisms as well as how to implement exercise in clinical settings to improve or protect against long-term cardiovascular disease outcomes are not clearly defined. In this review, we summarize the current evidence in the field of “exercise cardio-oncology” and emphasize the utilization of exercise to prevent and manage anthracycline-induced cardiotoxicities across high-risk and vulnerable populations diagnosed with cancer.

Clinical, Echocardiographic, and Biomarker Associations With Impaired Cardiorespiratory Fitness Early After HER2-Targeted Breast Cancer Therapy

Background

Cardiorespiratory fitness (CRF) is reduced in cancer survivors and predicts cardiovascular disease (CVD)–related and all-cause mortality. However, routine measurement of CRF is not always feasible.

Objectives

The purpose of this study was to identify clinical, cardiac biomarker, and imaging measures associated with reduced peak oxygen consumption (VO₂peak) (measure of CRF) early post–breast cancer therapy to help inform CVD risk.

Methods

Consecutive women with early-stage HER2+ breast cancer receiving anthracyclines and trastuzumab were recruited prospectively. Within 6 ± 2 weeks of trastuzumab completion, we collected clinical information, systolic/diastolic echocardiographic measures, high-sensitivity troponin I, B-type natriuretic peptide, and VO₂peak using a cycle ergometer. Regression models were used to examine the association between VO₂peak and clinical, imaging, and cardiac biomarkers individually and in combination.

Results

Among 147 patients (age 52.2 ± 9.3 years), the mean VO₂peak was 19.1 ± 5.0 mL O₂·kg⁻¹·min⁻¹ (84.2% ± 18.7% of predicted); 44% had a VO₂peak below threshold for functional independence (<18 mL O₂·kg⁻¹·min⁻¹). In multivariable analysis, absolute global longitudinal strain (GLS) (β = 0.58; P = 0.007), age per 10 years (β: -1.61; P = 0.001), and E/e’ (measure of diastolic filling pressures) (β = -0.45; P = 0.038) were associated with VO₂peak. GLS added incremental value in explaining the variability in VO₂peak. The combination of age ≥50 years, E/e’ ≥7.8, and GLS <18% identified a high probability (85.7%) of compromised functional independence, whereas age <50 years, E/e’ <7.8, and GLS ≥18% identified a low probability (0%). High-sensitivity troponin I and B-type natriuretic peptide were not associated with VO₂peak.

Conclusions

Readily available clinical measures were associated with VO₂peak early post–breast cancer therapy. A combination of these parameters had good discrimination to identify patients with compromised functional independence and potentially increased future CVD risk.

Skeletal Muscle Deconditioning in Breast Cancer Patients Undergoing Chemotherapy: Current Knowledge and Insights From Other Cancers

Breast cancer represents the most commonly diagnosed cancer while neoadjuvant and adjuvant chemotherapies are extensively used in order to reduce tumor development and improve disease-free survival. However, chemotherapy also leads to severe off-target side-effects resulting, together with the tumor itself, in major skeletal muscle deconditioning. This review first focuses on recent advances in both macroscopic changes and cellular mechanisms implicated in skeletal muscle deconditioning of breast cancer patients, particularly as a consequence of the chemotherapy treatment. To date, only six clinical studies used muscle biopsies in breast cancer patients and highlighted several important aspects of muscle deconditioning such as a decrease in muscle fibers cross-sectional area, a dysregulation of protein turnover balance and mitochondrial alterations. However, in comparison with the knowledge accumulated through decades of intensive research with many different animal and human models of muscle atrophy, more studies are necessary to obtain a comprehensive understanding of the cellular processes implicated in breast cancer-mediated muscle deconditioning. This understanding is indeed essential to ultimately lead to the implementation of efficient preventive strategies such as exercise, nutrition or pharmacological treatments. We therefore also discuss potential mechanisms implicated in muscle deconditioning by drawing a parallel with other cancer cachexia models of muscle wasting, both at the pre-clinical and clinical levels.

Traditional markers of cardiac toxicity fail to detect marked reductions in cardiorespiratory fitness among cancer patients undergoing anti-cancer treatment

AIMS

Left ventricular ejection fraction (LVEF) is standard of care for evaluating chemotherapy-associated cardiotoxicity, although global longitudinal strain (GLS) offers advantages. However, neither change in LVEF or GLS has been associated with short-term symptoms, functional capacity, or long-term heart failure (HF) risk. We sought to determine whether an integrative measure of cardiovascular function (VO2peak) that is strongly associated with HF risk would be more sensitive to cardiac damage induced by cancer treatment than LVEF, GLS, or cardiac biomarkers.

METHODS AND RESULTS

Patients (n = 206, 53 ± 13 years, 35% male) scheduled to commence anti-cancer treatment completed assessment prior to, and within 6 months after therapy. Changes in echocardiographic measures of LV function (LVEF, GLS), cardiac biomarkers (troponin and BNP), and cardiorespiratory fitness (VO2peak) were measured. LV function was normal prior to treatment (LVEF 61 ± 5%; GLS -19.4 ± 2.1), but VO2peak was only 88 ± 26% of age-predicted. After treatment, VO2peak was reduced by 7 ± 15% (equivalent of 7 years normal ageing, P < 0.0001) and the rates of functional disability (defined as VO2peak ≤ 18 mL/min/kg) almost doubled (15% vs. 26%, P = 0.016). In contrast, small, reductions in LVEF (59 ± 5% vs. 58 ± 5%, P = 0.03) and GLS (-19.4 ± 2.1 vs. -18.9 ± 2.2, P = 0.002) and an increase in troponin levels (4.0 ± 6.9 vs. 26.4 ± 26.2 ng/mL, P < 0.0001) were observed.

CONCLUSION

Anti-cancer treatment is associated with marked reductions in functional capacity that occur independent of reductions in LVEF and GLS. The assessment of VO2peak prior to, and following treatment may be a more sensitive means of identifying patients at increased risk of HF.

Cardiac and skeletal muscle predictors of impaired cardiorespiratory fitness post-anthracycline chemotherapy for breast cancer

This study aimed to characterize peak exercise cardiac function and thigh muscle fatty infiltration and their relationships with VO2peak among anthracycline-treated breast cancer survivors (BCS). BCS who received anthracycline chemotherapy ~ 1 year earlier (n = 16) and matched controls (matched-CON, n = 16) were enrolled. Resting and peak exercise cardiac function, myocardial T1 mapping (marker of fibrosis), and thigh muscle fat infiltration were assessed by magnetic resonance imaging, and VO2peak by cycle test. Compared to matched-CON, BCS had lower peak SV (64 ± 9 vs 57 ± 10 mL/m2, p = 0.038), GLS (- 30.4 ± 2.2 vs - 28.0 ± 2.5%, p = 0.008), and arteriovenous oxygen difference (16.4 ± 3.6 vs 15.2 ± 3.9 mL/100 mL, p = 0.054). Mediation analysis showed: (1) greater myocardial T1 time (fibrosis) is inversely related to cardiac output and end-systolic volume exercise reserve; (2) greater thigh muscle fatty infiltration is inversely related to arteriovenous oxygen difference; both of which negatively influence VO2peak. Peak SV (R2 = 65%) and thigh muscle fat fraction (R2 = 68%) were similarly strong independent predictors of VO2peak in BCS and matched-CON combined. Post-anthracyclines, myocardial fibrosis is associated with impaired cardiac reserve, and thigh muscle fatty infiltration is associated with impaired oxygen extraction, which both contribute to VO2peak.

Cancer therapy-related cardiac dysfunction: is endothelial dysfunction at the heart of the matter?

Significant improvements in cancer survival have brought to light unintended long-term adverse cardiovascular effects associated with cancer treatment. Although capable of manifesting a broad range of cardiovascular complications, cancer therapy-related cardiac dysfunction (CTRCD) remains particularly common among the mainstay anthracycline-based and human epidermal growth factor receptor-targeted therapies. Unfortunately, the early asymptomatic stages of CTRCD are difficult to detect by cardiac imaging alone, and the initiating mechanisms remain incompletely understood. More recently, circulating inflammatory markers, cardiac biomarkers, microRNAs, and extracellular vesicles (EVs) have been considered as early markers of cardiovascular injury. Concomitantly, the role of the endothelium in regulating cardiac function in the context of CTRCD is starting to be understood. In this review, we highlight the impact of breast cancer therapies on the cardiovascular system with a focus on the endothelium, and examine the status of circulating biomarkers, including inflammatory markers, cardiac biomarkers, microRNAs, and endothelial cell-derived EVs. Investigation of these emerging biomarkers may uncover mechanisms of injury, detect early stages of cardiovascular damage, and elucidate novel therapeutic approaches.

The role of exercise in the prevention of cancer therapy-related cardiac dysfunction in breast cancer patients undergoing chemotherapy: systematic review

AIMS

Breast cancer (BC) patients undergoing chemotherapy are at risk of developing cancer therapy-related cardiac dysfunction (CTRCD). Exercise has been proposed to prevent CTRCD; however, its effectiveness remains unclear. The aim of this systematic review was to establish the effect of exercise on global longitudinal strain (GLS) and left ventricular ejection fraction (LVEF) in BC patients undergoing chemotherapy, to determine if exercise can prevent the development of CTRCD.

METHODS AND RESULTS

Four databases (Medline, Scopus, eMbase, SPORTDiscus) were searched. Studies were eligible for inclusion if they measured GLS or LVEF prior to and following an exercise intervention of any length in BC patients undergoing chemotherapy and were published in English from 2000 onwards. Risk of bias was evaluated using the QUADAS-2 tool. Of the 398 studies screened, eight were eligible. Changes were similar in exercising (EX) and non-exercising (CON) groups for GLS (EX: pre: -19.6 ± 0.4, post: -20.1 ± 1.0, CON: pre: -20.0 ± 0.4, post: -20.1 ± 1) and LVEF (EX: pre: 58.5 ± 4.1%, post: 58.6 ± 2%, CON: pre: 56.6 ± 4.2%, post: 55.6 ± 4.6%). Exercise maintained or improved peak oxygen uptake (VO2peak) during chemotherapy, while declines were observed in non-exercising groups. The included studies were limited by methodological deficiencies.

CONCLUSION

The ability of exercise to prevent CTRCD is unclear. However, exercise positively impacts cardiorespiratory fitness in BC patients undergoing chemotherapy. Future research must address the methodological limitations of current research to understand the true effect of exercise in the prevention of CTRCD.

Exercise Cardiovascular Magnetic Resonance: A Review

While pharmacologic stress cardiovascular magnetic resonance imaging (MRI) is a robust noninvasive tool in the diagnosis and prognostication of epicardial coronary artery disease, clinical guidelines recommend exercise-based testing in those patients who can exercise. This review describes the development of exercise cardiovascular MRI protocols, summarizes the insights across various patient populations, and highlights future research initiatives. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 2.

The role of cardiac magnetic resonance imaging in the detection and monitoring of cardiotoxicity in patients with breast cancer after treatment: a comprehensive review

The use of chemotherapy medicines for breast cancer (BC) has been associated with an increased risk of cardiotoxicity. In recent years, there have been growing interests regarding the application of cardiovascular magnetic resonance (CMR) imaging, a safe and noninvasive modality, with the potential to identify subtle morphological and functional changes in the myocardium. In this investigation, we aimed to review the performance of various CMR methods in diagnosing cardiotoxicity in BC, induced by chemotherapy or radiotherapy. For this purpose, we reviewed the literature available in PubMed, MEDLINE, Cochrane, Google Scholar, and Scopus databases. Our literature review showed that CMR is a valuable modality for identifying and predicting subclinical cardiotoxicity induced by chemotherapy. The novel T1, T2, and extracellular volume mapping techniques may provide critical information about cardiotoxicity, in addition to other CMR features such as functional and structural changes. However, further research is needed to verify the exact role of these methods in identifying cardiotoxicity and patient management. Since multiple studies have reported the improvement of left ventricular performance following the termination of chemotherapy regimens, CMR remains an essential imaging tool for the prediction of cardiotoxicity and, consequently, decreases the mortality rate of BC due to heart failure.

Cardiopulmonary exercise testing - refining the clinical perspective by combining assessments

INTRODUCTION

Cardiorespiratory fitness (CRF) is now established as a vital sign. Cardiopulmonary exercise testing (CPX) is the gold-standard approach to assessing CRF.

AREAS COVERED

A body of literature spanning several decades clearly supports the clinical utility of CPX in those who are apparently health and at risk for chronic disease as well as numerous patient populations. While CPX, in and of itself, is a valid and reliable clinical assessment, combining findings with other available assessments may provide a more comprehensive perspective that enhances clinical decision making and outcomes. The current review will accomplish the following: (1) define key CPX measures based upon current evidence; and (2) describe the current evidence addressing the relationships between CPX and echocardiography, serum biomarkers, and cardiovascular magnetic resonance.

EXPERT OPINION

Cardiopulmonary exercise testing provides prognostic and diagnostic information in apparently healthy individuals, those at risk for one or more chronic conditions, as well as numerous patient populations. Moreover, if the goal of an intervention is to improve one or more systems integral to the physiologic response to exercise, CPX should be considered as a central assessment to gauge therapeutic efficacy. To further refine the information obtained from CPX, combining other assessments has demonstrated promise.

The Utility of Cardiac Reserve for the Early Detection of Cancer Treatment-Related Cardiac Dysfunction: A Comprehensive Overview

With progressive advancements in cancer detection and treatment, cancer-specific survival has improved dramatically over the past decades. Consequently, long-term health outcomes are increasingly defined by comorbidities such as cardiovascular disease. Importantly, a number of well-established and emerging cancer treatments have been associated with varying degrees of cardiovascular injury that may not emerge until years following the completion of cancer treatment. Of particular concern is the development of cancer treatment related cardiac dysfunction (CTRCD) which is associated with an increased risk of heart failure and high risk of morbidity and mortality. Early detection of CTRCD appears critical for preventing long-term cardiovascular morbidity in cancer survivors. However, current clinical standards for the identification of CTRCD rely on assessments of cardiac function in the resting state. This provides incomplete information about the heart's reserve capacity and may reduce the sensitivity for detecting sub-clinical myocardial injury. Advances in non-invasive imaging techniques have enabled cardiac function to be quantified during exercise thereby providing a novel means of identifying early cardiac dysfunction that has proved useful in several cardiovascular pathologies. The purpose of this narrative review is (1) to discuss the different non-invasive imaging techniques that can be used for quantifying different aspects of cardiac reserve; (2) discuss the findings from studies of cancer patients that have measured cardiac reserve as a marker of CTRCD; and (3) highlight the future directions important knowledge gaps that need to be addressed for cardiac reserve to be effectively integrated into routine monitoring for cancer patients exposed to cardiotoxic therapies.

Exercise Intolerance in Anthracycline-Treated Breast Cancer Survivors: The Role of Skeletal Muscle Bioenergetics, Oxygenation, and Composition

BACKGROUND

Peak oxygen consumption (VO₂ ) is reduced in women with a history of breast cancer (BC). We measured leg blood flow, oxygenation, bioenergetics, and muscle composition in women with BC treated with anthracycline chemotherapy (n = 16, mean age: 56 years) and age- and body mass index-matched controls (n = 16).

MATERIALS AND METHODS

Whole-body peak VO₂ was measured during cycle exercise. ³¹ Phosphorus magnetic resonance (MR) spectroscopy was used to measure muscle bioenergetics during and after incremental to maximal plantar flexion exercise (PFE). MR imaging was used to measure lower leg blood flow, venous oxygen saturation (S_v O₂ ), and VO₂ during submaximal PFE, and abdominal, thigh, and lower leg intermuscular fat (IMF) and skeletal muscle (SM).

RESULTS

Whole-body peak VO₂ was significantly lower in BC survivors versus controls (23.1 ± 7.5 vs. 29.5 ± 7.7 mL/kg/minute). Muscle bioenergetics and mitochondrial oxidative capacity were not different between groups. No group differences were found during submaximal PFE for lower leg blood flow, S_v O₂ , or VO₂ . The IMF-to-SM ratio was higher in the thigh and lower leg in BC survivors (0.36 ± 0.19 vs. 0.22 ± 0.07, p = .01; 0.10 ± 0.06 vs. 0.06 ± 0.02, p = .03, respectively) and were inversely related to whole-body peak VO₂ (r = -0.71, p = .002; r = -0.68, p = .003, respectively)_. In the lower leg, IMF-to-SM ratio was inversely related to VO₂ and O₂ extraction during PFE.

CONCLUSION

SM bioenergetics and oxidative capacity in response to PFE are not impaired following anthracycline treatment. Abnormal SM composition (increased thigh and lower leg IMF-to-SM ratio) may be an important contributor to reduced peak VO₂ during whole-body exercise among anthracycline-treated BC survivors.

IMPLICATIONS FOR PRACTICE

Peak oxygen consumption (peak VO₂ ) is reduced in breast cancer (BC) survivors and is prognostic of increased risk of cardiovascular disease-related and all-cause mortality. Results of this study demonstrated that in the presence of deficits in peak VO₂ 1 year after anthracycline therapy, skeletal muscle bioenergetics and oxygenation are not impaired. Rather, body composition deterioration (e.g., increased ratio of intermuscular fat to skeletal muscle) may contribute to reduced exercise tolerance in anthracycline BC survivors. This finding points to the importance of lifestyle interventions including caloric restriction and exercise training to restore body composition and cardiovascular health in the BC survivorship setting.