Cardiotoxicity in cancer patients: beyond the left ventricular ejection fraction.

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UNIVERSITA’ DI PISA

SCUOLA DI SPECIALIZZAZIONE IN MALATTIE DELL’APPARATO

CARDIOVASCOLARE

Cardiotoxicity in cancer patients: beyond the left ventricular

ejection fraction

Advisors: Prof. Mario Marzilli, University of Pisa, Italy Dr. Lucia Venneri, CNR Pisa, Italy

Candidate: Dr. Francesca Calicchio

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SUMMARY

Life-expectancy for patients with cancer is steadily improving, with an increasing rate of treatment related complications. Antineoplastic therapy employed in cancer treatment is frequently complicated by the development of cardiotoxicity. Cardiovascular complications can be different, ranging from heart failure, myocardial ischemia or infarction to hypertension, arrhythmias and thromboembolism. It is therefore mandatory to early recognize and treat cardiovascular side effects related to chemotherapy drugs. Echocardiography has been and it is still the cornerstone in the diagnosis and follow-up of cardiac dysfunction due to its availability, safety and versatility. The most used parameter to evaluate cardiac dysfunction in this context is the left ventricular ejection fraction (LVEF) and current European Society of Echocardiography and American Society of Echocardiography guidelines for the evaluation of adult patients during and after cancer therapy are based on LVEF. However this parameter has several limits and may mask cardiac dysfunction. Recently developed strain imaging may provide a more sensitive and early detection of altered left ventricular function.

In the present study we evaluated 53 patients (age 53 ± 13 years, women 64%) on cancer drug therapies referred to the cardio-oncology clinic of the Royal Brompton Hospital in London. All patients had 2D echo-derived LVEF ≥55% and echo images suitable to

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speckle tracking analysis for global longitudinal (GLS), circumferential (GCS) and radial strain (GRS). Concomitant troponin I and BNP levels were measured and 43 (81%) patients underwent CMR imaging. The 2D strain data were compared to 25 healthy age matched controls using the student t test. Conventional echocardiographic parameters were substantially normal, including diastolic measurements All strain parameters were significantly lower in patients on cancer drug therapies compared to controls. In the cancer population (n=53) we found mean global peak systolic values of global longitudinal strain (GLS) global circumferential strain (GCS) and global radial strain (GRS) respectively of -19.8 ± 3.3%, -23.4 ± 4.8% and 29.7 ± 14%. In the 25 controls strain imaging values were respectively -22 ± 2% for GLS, -29.5 ± 5% for GCS and 42 ± 10% for GRS.

CMR showed loss of torsion and/or fibrosis in 10(23%) patients with no correlation to strain values. BNP was elevated in 34(64%) patients with no differences in strain values compared to those with normal BNP values. Troponin I was elevated in only one patient. Intra-observer reproducibility carried out in a subgroup of 20 random selected cancer patients revealed good correlation for global longitudinal and circumferential strain (ICC 0.8; r=0.7) and moderate correlation for global radial strain (ICC 0.7; r=0.6) while inter-observer variability showed moderate correlation for all the three parameters (ICC 0.7; r=0.5).

In our study cancer patients on current chemotherapy drugs with preserved left ventricular ejection fraction (LVEF ≥ 55%) showed significantly lower GLS, GCS and GRS values when compared to our echo-lab normal reference values (p<.05).

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In our study, despite having a normal LVEF, patients on cancer drug therapies had evidence of sub-clinical myocardial dysfunction affecting all myocardial layers and in particular radial function. Strain can be therefore a sensitive tool to detect early chemotherapy related cardiotoxicity and to prevent morbidity and mortality through close follow-up and appropriate cardiac therapy. CMR findings and BNP levels may provide additional complementary information. The clinical relevance of these findings requires further study.

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LIST OF FIGURES

Figure 1.1. Current and estimated cancer survivors in the United States from 1977 to 2012……

Figure 1.2. Type I and type II cardiotoxicity...

Figure 1.3. Relation between drug-cancer exposure and cardiovascular side effects...

Figure 1.4. Cardiovascular side effects of radiation exposure...

Figure 1.5. Myocardial fibers orientation and related deformation indices...

Figure 4.1 The study protocol...

Figure 4.2 Cardiovascular risk factors in the study group...

Figure 4.3. Type of cancer in the study group...

Figura 4.4. GLS and GRS in a cancer patient with normal LVEF... 16 17 20 23 28 43 44 46 49

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LIST OF TABLES

Table 1.1. Cardiovascular side effects and cancer drugs... .22

Table 1.2. Terms and definition of speckle tracking echocardiography... 29

Table 4.1. Baseline clinical and echocardiographic characteristics of cancer patients... 48

Table 4.2. Intra-observer reproducibility of strain measurements... 51

Table 4.3. Inter-observer reproducibility of strain measurements... 51

Table 4.4. Baseline clinical and echocardiographic characteristics of controls... 52

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1. INTRODUCTION

1.1 CANCER EPIDEMIOLOGY

The number of people currently living who have been diagnosed with cancer has been steadily increasing. This is due to two complementary reasons: the increase of cancer survivors and the aging of the population.

Age is one of the most important risk factors for developing cancer and for the majority of the most common cancers, more than half of cases occurs in individuals who are 65 year or older at the time of diagnosis. Breast cancer and ovarian cancer represent an exception to this pattern because they occur in younger patients.

Each year in Europe around 3 million patients are diagnosed with cancer. In 2008, an estimated 39 million U.S. citizens (13%) were 65 years or older. By the year 2030, this proportion is projected to increase to 19.3% and also the over 85 and older will increase more than three times by the 2050 [Parry et al, 2011].

Since 1971, when the "war against cancer" was launched, there has been an increase in the number of survivors thanks to many advances in cancer detection, treatment, and supportive care. [Thavendiranathan et al., 2014]. Increased survival and older age are accompanied by greater risk for developing subsequent cancers. In the United States the

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number of cancer survivors is projected to increase by 31% to almost 18 million during the next ten years (see Figure 1.1). They are especially women with breast cancer and men with prostate cancer because of the low mortality rate of these two cancers. The number of new cancer cases and the number of long-term survivors is projected to increase over the next decade. From 2012 to 2022 the number of survivors (< 5 years from diagnosis) will increase from 4.9 million to 6.0 million or 22%; and the number of survivors (≥ 5 years from diagnosis) will increase from 8.7 million to 11.9 million or 37% [De Moor J et al., 2013].

1.2 CARDIOTOXICITY: DEFINITION AND CLASSIFICATION

Cardiotoxicity is one of the most frequent and devastating consequences of antineoplastic therapy and it can gravely affect patient prognosis. Cardiac dysfunction related to exposure to cancer therapeutics was first recognized in 1960s. Common cardiovascular complications include left ventricular dysfunction, heart failure (HF), hypertension (HTN), thromboembolism, arrhythmias and myocardial ischemia [Yeh, 2009].

Due to the increasing number of cancer survivors together with the introduction of new antineoplastic drugs, there is growing interest in diagnosis, management and prevention of cardiac side effects. Contemporary management of patients with cancer should include careful consideration of potential cardiotoxicity during therapy, with a focus on early detection and intervention.

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Historically, several definitions of cardiotoxicity have been proposed [Khouri et al., 2012].

The most used definition is a ≥5% reduction in symptomatic patients (or ≥10% reduction in asymptomatic patients) in the left ventricular ejection fraction (LVEF) from baseline to an LVEF <55% [Seidman, 2002].

A cardinal distinction is between non-reversible (type I) and reversible (type II) cardiotoxicity (see Figure 1.2)

Type I cardiotoxicity is determined by all the anthracyclines (doxorubicin, epirubicin, idarubicin) and mitoxantrone and it is dose-dependent. It is related to the production of reactive oxygen species causing myocyte damage and apoptosis, thus leading to irreversible damage. It involves increased risk to cause long-term cardiac dysfunction and increased morbidity and mortality. Cardiac function may be preserved thanks to early detection and prompt treatment with antiremodeling therapy [Plana et al., 2013].

Type II cardiotoxicity is classically caused by trastuzumab as well as other small molecules such as pertuzumab, bevacizumab, and tyrosin kinase inhibitors (imatinib, sunitinib, sorafenib, lacatinib). The hypothesized mechanism seems to be related to transient damage of contractile cells or to the increased afterload. It is not dose dependent and can be reversible and functional recovery is often observed after interruption of the chemotherapy.

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Figure 1.1. Current and estimated cancer survivors in the United States from 1977 to 2022 [De Moor et al., 2014].

This classification has technical limitations because often different types of cancer drugs are given sequentially or concomitantly in the same patient (for example anthacyclines and trastuzumab in breast cancer) resulting in more complex assessment of related cardiac dysfunction [Plana et al., 2013].

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Figure 1.2. Type I and type II cardiotoxicity.

1.3 CARDIOVASCULAR SIDE EFFECTS OF CANCER THERAPY

Cardiotoxicity classification in literature is based on the different type of drug, mechanism of action and onset of symptoms.

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- anthracyclines (Doxorubicin, Epirubicin, Idarubicin); - alkylating agents (Cyclophosphamide, Ifosfamide, Cisplatin);

- monoclonal antibody-based tyrosine kinase inhibitors (Bevacizumab, Trastuzumab);

- pyrimidine analogues (Fluorouracil, Capecitabine); - antimicrotubule agents (Docetaxel, Paclitaxel); - antimetabolites (Clofarabine);

- proteasome inhibitor (Bortezomib);

- small molecule tyrosine kinase inhibitors (Dasatinib, Lapatinib, Sunitinib, Imatinib, Sorafenib).

Each cancer drug acts through different mechanism and cardiovascular side effects are time and dose-dependent. Often, since the heart has significant cardiac reserve, cardiac damage cannot be detected even until decades after receiving the treatment (see Figure 1.3).

Anthracyclines, antimetabolites and alkylating agents can induce permanent myocardial cell injury. More in detail anthracyclines, one of the most used cancer drug, can cause both early cardiac side effects (such as dysrhythmia, repolarization changes, pericarditis) and late cardiotoxicity that leads to cardiomyopathy and systolic heart failure [Smith et al.,

2010]. Mitoxantrone, an anthracycline analogue, can result in the same cardiotoxicity as anthracyclines [Saletan, 1987]. Cyclophosphamide can cause haemorrhagic cell necrosis and severe heart failure [Braverman at al., 1991] Cisplatin has also been associated with

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Trastuzumab is a monoclonal antibody against the HER2/erbB2 receptor and it is frequently used in combination with chemotherapy in women with HER2-overexpressed breast cancer. Concomitant use of trastuzumab with anthracycline hugely increases the risk of cardiotoxicity thus it is generally used after anthracyclines.

Angiogenesis inhibitors, either antibodies against VEGF (bevacizumab) or small molecule TKIs (sunitinib, sorafenib) are employed in a variety of solid tumours, including metastatic colorectal, renal cell, hepatocelluar cancer, and gastro-intestinal stromal tumours. They may cause cardiac dysfunction with heart failure.

Many types of cancer drugs may cause, beyond the left ventricular dysfunction, a wide spectrum of cardiovascular side effects from arterial hypertension to vasospastic and thromboembolic ischaemia, thromboembolic events or electrocardiographic abnormalities [Suter et al., 2013].

The most common cardiovascular side effects of cancer therapeutics are summarized in Table 1.1.

Studies in animal models (mice with cancer cachexia) have shown a firm relationship between cancer and heart muscle dysfunction. Studies conducted in animal models of cancer cachexia have demostrated that proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), play an important role in inducing muscle wasting and can cause early systolic dysfunction of the heart.

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Figure 1.3. Relation between drug-cancer exposure and cardiovascular side effects [by Suter TM, 2013].

Several explanations for contractile impairment of the cardiomyocytes can be derived from the literature related to the oxidation of proteins involved in ATP production and muscle contraction or over expression of myosin heavy chain. Xu at al. [2011] hypothesized first that tumor growth can directly impact contractile function in cardiomyocytes. They showed an increase in left ventricular systolic diameter (LVSD) and decrease in % fractional shortening, indicative of systolic dysfunction, without any evidence of diastolic dysfunction in vivo [Xu et al., 2011; Tian et al., 2010, Argiles et al.,

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These findings imply that cardiac evaluation has to be part of the clinical evaluation in cancer patients.

1.4 CARDIOVASCULAR SIDE EFFECTS OF RADIATION THERAPY

In addition to chemotherapy, also radiotherapy (RT) through micro and macrovascular damage can affect cardiac function and structures with acute or long term onset patterns (see Figure 1.4 for a description).

Factors that may influence radiation cardiac effects are the cumulative dose, the concomitant use of chemotherapeutic agents (as anthracyclines), left chest irradiation, presence of tumour in or next to the heart and pre-existing cardiovascular risk factors or diseases. Microvascular damage both of the endothelium and valves produces inflammatory response with thickening and fibrosis of vessels and valve leaflets. Macrovascular injury accelerates atherosclerosis and can lead to coronary artery disease and ischemia with worsening in systolic and diastolic function [Lancellotti et al., 2014].

The most common clinical manifestations of the above described pathophysiological mechanism include valvular heart disease, pericarditis, coronary artery disease, myocardial ischemia and restrictive cardiomyopathy.

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Cardiac side effect Drug Frequency Reversibility Heart Failure Anthracyclines

Cisplatin Cyclophosphamide Trastuzumab Bevacizumab Sunitinib Imatinib Dose related Rare Rare Variable Low Low Rare Minimal Unknown Partial High Partial Unknown High Myocardial ischemia Pyrimidine analogues Moderate High Arterial hypertension Bevacizumab, Sunitinib,

Sorafenib

Moderate Unknown

Thromboembolism Cisplatin, Bevacizumab, Sunitinib, Sorafenib

Moderate Variable

Arrhythmia/QT prolongation Lapatinib, Sunitinib Rare Unknown

Table 1.1. Cardiovascular side effects and cancer drugs.

There are no clear guidelines regarding the optimal screening and follow-up timing of patients with previous radiation exposure but echocardiography, together with cardiac magnetic resonance, computed tomography and nuclear cardiology, play an important

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role in detecting fibrosis, myocardial oedema or inflammation and other radiation cardiac side effects.

Figure 1.4. Cardiovascular side effects of radiation exposure.

1.5 ASSESSMENT OF CARDIOVASCULAR RISK IN CANCER PATIENTS

In cancer patient population we have a wide range of techniques to assess global cardiovascular risk.

Electrocardiography (ECG) is a wide available and inexpensive tool to detect conduction disturbances and signs of cardiomyopathy. Some chemotherapics, indeed, can produce

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QT prolongation or myocardial ischemia or repolarization abnormalities. Many studies describe corrected QT prolongation as an early marker of cardiac dysfunction [Nakamae, 2000] but there are no data on long term prognosis. Moreover ECG does not provide information on left ventricular function and can be modified by different and concurrent medications.

Echocardiography allows to study systolic and diastolic function and is used especially to assess LVEF and its changes during treatment. According to the European Society of Cardiology, LVEF in the range of 53-73% has to be classified as normal and chemotherapy-related cardiac dysfunction is defined as a decrease in LVEF >10% to a value <53%, which is the normal reference value for 2D echocardiography. It can be symptomatic or asymptomatic and can be reversible (to within 5 percentage points of baseline), partially reversible (improved by 10 percentage points but remaining >5 percentage points below baseline) and irreversible (remaining within 10 percentage points of the nadir) [Plana et al., 2014]. The calculation of ejection fraction should be done ideally with 3D otherwise with the modified biplane Simpson. The quantification of left ventricle longitudinal function can be assessed by medial and lateral excursion of mitral annulus (MAPSE) or with measurement of peak systolic velocity (S’) by tissue Doppler imaging (TDI). In addition assessment of diastolic function and right ventricle chamber and function is crucial and should be performed in each cancer patients. Echocardiography is very versatile and can be repeated a lot of times due to its safety and several studies show the best method to evaluate the patient before, during and after the chemotherapy is echocardiography. Unfortunately LVEF is not the most reliable

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parameter due to interobserver variability and load dependency while diastolic measurements and especially the newer strain imaging might provide early detection in cardiac function.

Stress echocardiography is often used in cancer patients for its diagnostic and prognostic value. It helps to rule out ischemia in patients receiving cardiotoxic drugs and also allows the determination of myocardial contractile reserve in patient with chemotherapy related cardiac dysfunction.

Cardiac magnetic resonance imaging is very useful to analyze both structural and functional parameters in chemotherapy related cardiac dysfunction with high resolution and without radiation exposure. Calculation of LVEF is reliable and it has shown very good correlation with LVEF assessed by 2D and 3D echocardiography. Moreover by using the late gadolinium enhancement it allows to recognize fibrosis (late gadolinium enhancement) thus providing important functional information. On the other hand it has high costs, it is not widely available and in some cases there are absolute contraindications to the exam. It is still not known if magnetic resonance can detect early cardiovascular dysfunction related to cancer drugs.

MUGA (multiple gated acquisition) scintigraphy, together with echocardiography, is the most widely accepted tool to assess LVEF during treatment with cancer drugs [Jannazzo, 2008]. It has low interobserver variability and high reproducibility. However it involves substantial radiation exposure and has very limited value for subclinical cardiac dysfunction and early detection of cardiotoxicity.

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1.6 SPECKLE TRACKING ECHOCARDIOGRAPHY: A PROMISING TOOL FOR THE EARLY DETECTION OF SUBCLINICAL LEFT VENTRICULAR DYSFUNCTION

Echocardiographic strain imaging, also known as deformation imaging, is a technological advancement and has been developed to objectively quantify regional myocardial function and it was originally introduced as a product of tissue doppler imaging (TDI) while speckle tracking is a more recent extension of strain imaging. Two-dimensional strain is an automated and quantitative technique for the measurement of global long-axis function from gray-scale images. It is not angle-dependent and has been shown to correlate well with LVEF measured both by echocardiography and cardiac magnetic resonance [Stanton, 2009]. Strain imaging can now be performed during routine echocardiography and has provided greater understanding of the pathophysiology of cardiac ischemia and infarction, the effects of valvular disease on myocardial function, primary diseases of the myocardium, assessment of dyssynchrony for cardiac resynchronization therapy (CRT), and the mechanics of diastolic function. Moreover several potential clinical applications can derive from both 2D and 3D speckle tracking echocardiography. An important advantage of strain or strain rate measurement is they are not load dependent. Currently myocardial deformation can be measured using TDI and 2 and 3 dimensional speckle tracking echocardiography.

Speckle-tracking echocardiography is based on an analysis of the spatial dislocation (referred to as tracking) of speckles (defined as spots generated by the interaction between the ultrasound beam and myocardial fibers) on routine 2-dimensional

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echocardiograms. The displacement tracking of speckles during the cardiac cycle allows semiautomated elaboration of myocardial deformation in three spatial directions: longitudinal, radial, and circumferential. The semiautomated nature of speckle-tracking echocardiography guarantees good intraobserver and interobserver reproducibility. Single speckles are combined in functional units (kernels) that are univocally identifiable given the peculiar disposition of the speckles. Thus, each kernel can be tracked by software during the entire cardiac cycle. Through analysis of the motion of each kernel that composes a routine 2-dimensional gray scale image, the system can calculate displacement, the rate of displacement (velocity), deformation (strain), and the rate of deformation (strain rate) of the selected myocardial segments and LV rotation. Each sample for a speckle-tracking echocardiographic analysis must be obtained by averaging at least 3 consecutive heart cycles, setting the frame rate of the routine 2-dimensional image acquisition between 60 and 110 frames per second. [Perk et Gorcsan 2007a, 2011b].

Strain is a therefore dimensionless index reflecting the total deformation of the ventricular myocardium during a cardiac cycle as a percentage of its initial length (reported as percentage). Radial strain has positive curves, reflecting myocardial thickening. Conversely, longitudinal and circumferential strains have negative curves, reflecting myocardial shortening (see Figure 1.5 ).

Strain rate (SR) is the rate of deformation or stretch (reported as strain_1_{) [Geyer}et al., 2010; Mor-Avi et al., 2011]. Both strain and strain rate can be measured in the

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studies have shown the strain rate is less dependent on LV load variations than strain [Marwick TH 2005].

Figure 1.5. Myocardial fibers orientation and related deformation indices [Gorcsan et al., 2011].

The obtained images are processed using specific software usually available on dedicated workstations, allowing offline semi automated analysis. The endocardial surface of the myocardial segment analyzed is manually traced in apical and/or short axis views. Then an epicardial surface tracing is automatically generated by the software creating a region of interest (ROI). After manual adjustment of the ROI the system can automatically divide the region of interest into segments, and the tracking quality for each segment is automatically marked as acceptable or unacceptable. There is the possibility to manually correct the track of each segment. Segments considered inadequate are rejected by the

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software and can be excluded from the analysis. Finally, the software generates strain curves for each segment and from these curves, regional values as well as and global peak and time-to-peak values can be achieved [Mondillo et al., 2011].

Term Definition

Strain (S) Myocardial deformation .

Strain rate (SR) Myocardial deformation rate velocity.

Global Longitudinal Strain (GLS) Base-to-apex–directed myocardial deformation. Global Circumferential Strain (GCS) Left ventricular myocardial shortening along the

circular perimeter observed in a short-axis view. Global Radial Strain (GRS) Myocardial deformation directed radially toward

the center of the left ventricular cavity.

Table 1.2. Terms and definition of speckle tracking echocardiography.

It must be taken into account that a variety of parameters may potentially influence the measurement of strain, including cardiac factors (LV size, wall thickness), patients-related features (anthropometric variables, ethnicity, age, gender, race), hemodynamic factors (blood pressure, heart rate) [Marwick, 2009]. Another cause for concern is the variation in recorded measurements among different vendors due to differences in the softwares used to calculate the deformation. Among the deformation indices global longitudinal strain (GLS) appears to be the simplest deformation parameter, and probably the closest to

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routine clinical application while strain rate is noisier and less reproducible and thus less utilized in clinical studies.

Substantial potential limitations of this technique are its strict dependence on the high-quality 2-dimensional images which are necessary for obtaining an optimal definition of the endocardial border, and dependence on frame rate.

According to a recently published meta-analysis by Marwick et al. normal values for global

longitudinal strain are -19.7% (95%CI, -20.4% to -18.9%), for global circumferential strain -23.3% (95% CI, -24.6% to -22.1%), and for normal radial strain 47.3% (95% CI, 43.6% to 51.0%). They concluded that variations among different normal ranges seemed to be associated with differences in systolic blood pressure in different patient groups [Yingchoncharoen et al., 2013] therefore it is mandatory take into account systolic blood

pressures values.

1.7 SPECKLE TRACKING ECHOCARDIOGRAPHY IN CANCER PATIENTS

Early detection of cardiotoxicity is especially based on cardiac imaging to identify a reduction in left ventricular function. However, ejection fraction has important limitations. First, it is an imperfect parameter because of load dependency and technique-related variability which can be higher than the thresholds used to define cardiotoxicity [Otterstad, 1997]. Second the LVEF reduction is often a late phenomenon which fails to detect early subtle changes and often reflects advanced damage associated with a poor prognosis [Eidem, 2008]. Therefore, there has been a growing interest in markers of early

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myocardial damage (such as strain and strain rate) to predict ventricular dysfunction or the development of heart failure, so that preventive strategies with cardioprotective medications (for example angiotensin-converting enzyme inhibitors and beta-blockers) could be implemented.

A growing body of literature confirms the use of myocardial deformation parameters also to detect early myocardial injury and to forecast cardiac toxicity in patients receiving cancer therapy.

Decrease in longitudinal strain and strain rate were detected in patients treated with anthracyclines (sometimes in association with trastuzumab and taxanes) [Sawaya et al.,

2012] and in one small study earlier decrease in radial strain was found in patients treated with the same cancer drug [Jurcut et al., 2008].

Ho et al. [2010] reported the long-term effects of chemotherapy on myocardial function

in asymptomatic breast cancer survivors using strain imaging. They found that the chemotherapy group had reduced GLS compared to normal controls even with similar EF while global radial speckle tracking strain did not differ significantly between the 2 groups.

Global longitudinal strain is therefore one of the newer parameter to detect early sub-clinical left ventricular dysfunction. Ideally all the patients should have baseline referral values and the most convenient measurement would be the difference in serial echocardiograms. A recent study by Negishi et al. [2013] showed in patients with baseline

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clinically meaningful. In absence of baseline values a cut-off of -19% has been recently proposed by the European Society of echocardiography [Plana et al.2014].

Most of the studies have been conducted in women with breast cancer after exposure to anthacyclines and trastuzumab. Due to the small study population there are different findings in literature regarding the strain deformation indices in cancer patients.

Stoodley et al. [2011] showed reduced left ventricular systolic strain (longitudinal and

radial, both global and regional) immediately after anthracyclines treatment in 52 women with breast cancer.

GLS resulted as an independent early predictor of later reductions in EF in a study conducted by Negishi et al. [2013] in breast cancerwomen treated with trastuzumab. A decrease in longitudinal strain after epirubicin exposure was the best independent and accurate predictor of cardiotoxicity in a cohort of 40 women with breast cancer studied by Florescu et al. [2014].

Another study by Sawaya et al. in women with breast cancer and exposed to anthacyclines

and trastuzumab therapy showed significant reduction in longitudinal strain from baseline to 3 months.

Not only the systolic longitudinal myocardial strain but also biomarkers have been widely investigated in literature. Troponin I measured after the exposure to anthracyclines seems to be an useful sign in the prediction of subsequent cardiotoxicity. Indeed in patients treated with anthracyclines and trastuzumab a decrease in longitudinal strain from baseline to 3 months and detectable cardiac troponin plasma concentrations at 3 months

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were independent predictors of the development of cardiotoxicity at 6 months while the LVEF and NT pro BNP failed to predict cardiotoxicity [Sawaya 2012].

Global systolic strain as a more sensitive marker of cardiac dysfunction has been confirmed also by Stoodley et al [2013] in seventy-eight HER2/neu negative breast cancer

patients up to 12 months after cancer drug administration.

Focusing the attention on the GLS percentage change some authors have demonstrated a >15.9% decrease in GLS and a >0.004 ng/mL elevation in TnT from baseline to the third cycle of chemotherapy predicted later cardiotoxicity in 75 patients with non-Hodgkin lymphoma treated with anthracyclines [Kang at al., 2014].

Regarding the role of radiation therapy there is evidence in literature in women receiving adjuvant RT to the breast or chest wall and lymph nodes that strain rate imaging can identify reductions in LV function not detectable by conventional echocardiographic function parameters and can last several months after the exposure.

A significant decrease in longitudinal strain and SR was observed immediately after RT and at 8 and 14 months after RT for left-sided breast cancer patients in a study on 75 women with breast ca. Moreover, mean TnI levels for the left- sided patients were significantly elevated after RT compared with before RT, whereas TnI levels of the right-sided patients remained unaffected suggesting a possible relation with the radiation dose and volume. [Erven et al., 2012]. Further studies are needed to assess the clinical impact

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1.8 FUTURE AND COMPLEMENTARY STRATEGIES

Beside the well recognized strategies to assess cardiovascular dysfunction we have other parameters whose clinical impact and prognostic value has to be further evaluated. Serum biomarkers such as natriuretic peptides, (n-terminal pro-brain natriuretic peptide, brain natriuretic peptide, and atrial natriuretic peptide) and cardiac troponin I and T are easily accessible and offer low interobserver variability. Persistent high levels of cardiac troponin I or N-terminal pro B-type natriuretic peptide concentrations seem to identify patients at risk for cardiotoxicity [Sandri et al., 2005; Cardinale et al., 2004]. Unfortunately

their exact predictive value is not certain and normal.and abnormal values are not well determined. Biomarkers may be useful when integrated with conventional cardiac imaging.

Endothelial damage biochemical markers might be a useful tool to investigate early cardiotoxicity. Many vasoactive factors such as cytochines and adhesion molecules are implicated in the endothelial dysfunction and can accelerate the atherosclerotic process. However the exact factors implicated as well as their predictive role remain still unknown. The nuclear tracer 123-Iodine-metaiobenzylguanidine is still at the beginning and it used to study myocardial adrenergic neurotransmitter system, which can be compromised in patient receiving anthracyclines. This technique might allow to detect changes in functional and metabolic processes but the predictive value is not defined. In addition it is more expensive and radiation exposure has to be taken into account.

Genetic variations are a wide field of interest in patients with cancer and their determination is minimally invasive. Genoma screening identified several single

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nucleotide polymorphisms associated with genetic predisposition for increased sensitivity to chemotherapy; for example nicotinamide adenine dinucleotide phosphate (

An integrated approach with the use of conventional echocardiography, tissue Doppler imaging and more advanced techniques is of paramount importance in the subset of cardio-oncology patients to better define the appropriate therapeutic strategy.

NADPH) oxidase subunit polymorphism are involved in doxorubicin metabolism and formation of reactive oxygen species. Even if genetic variations might be useful to predict susceptibility to cardiac to cardiac toxic effects a lot of polymorphisms can occur making difficult to identify the most relevant variations.

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2. AIM OF THE STUDY

The aim of the present study was to evaluate the value of myocardial strain parameters (using speckle tracking echocardiography) in detecting early subclinical LV dysfunction in cancer patients with a normal ejection fraction on current cancer drug therapies.

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3. METHODS

3.1 STUDY POPULATION

From March 2014 to January 2015 one hundred and fourteen consecutive cancer patients referred to the Cardio-Oncology Clinic of the Royal Brompton Hospital (London, UK) for cardiovascular assessment were prospectively analyzed.

Inclusion criteria were age >18 years and previous cancer diagnosis. Exclusion criteria were poor acoustical window causing suboptimal images (n=7), concomitant presence of atrial fibrillation (n=4), more than mild valvular heart disease (n=3), previous PCI or CABG (n=3); severe cardiac dysfunction with LVEF <35% (n=2) . Among the remaining 95 patients we excluded 19 with no previous exposure to chemotherapy and LVEF<55%.

The study protocol was approved by the local ethics committees.

3.2 ECHOCARDIOGRAPHY,CARDIAC MAGNETIC RESONANCE AND BIOMARKERS

All subjects underwent conventional echocardiography (M-Mode, 2D, Doppler and TDI) and, in a selected cohort of 20 patients, 3D echocardiography was also carried out. A

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Philips iE33 machine (Philips, The Netherlands) was used to acquire images and measurements were taken according the current guidelines of the European Society of Echocardiography. Mean frame rate in the acquisition of echocardiographic images was 60 Hz. All conventional echocardiographic parameters were acquired including assessment of diastolic function (E/A ratio). Tissue Doppler derived indices were measured using the four-chamber view. Peak systolic (S’), early diastolic (E’) mitral annular velocities and both medial and lateral E/E’ ratio were calculated. The modified biplane Simpson’s method was used to calculate LVEF. Normal LVEF was defined as ≥55% as stated in the recent consensus by the European Society of Echocardiography. Right ventricle function evaluation including TAPSE and S’ velocity values was recorded.

Sector size and depth were adjusted for each patient to achieve optimal visualization at the highest possible frame rate.

Cardiac magnetic resonance was performed using a 1,5 T scanner (mobile Siemens Avanto 1.5T scanner.).

Blood tests to detect Troponin I and brain natriuretic peptide (BNP) levels were taken from all the subjects the same day of echocardiography. Cut-off levels were considered 40 ng/L for Troponin I and >20 ng/L for BNP.

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3.3 STRAIN MEASUREMENTS

Two-dimensional speckle tracking echocardiography was performed to assess myocardial deformation in all the three direction (longitudinal, circumferential and radial) using the commercially available TomTec software (2D Cardiac Performance Analysis Version 1.1, TomTec Imaging Systems gmbH, Unterschleissheim, Germany) in all the patients. The frame in which the endocardial border was better seen was identified and manual tracing was carried out to provide peak global systolic values in four, three and two chamber for longitudinal values and in basal, med-papillary and apical view in short axis for circumferential and radial values. Mean GLS resulted from the average of the three apical views while mean GCS and GRS were obtained from the average of the three parasternal short-axis plane.

3.4 REPRODUCIBILITY

Intra and interobserver variability for strain deformation indices were evaluated in 20 random patients by two observers using the intra-class correlation coefficient (ICC) and Pearson correlation coefficient (Pearson’s r).

3.5 STATISTICAL ANALYSIS

Statistical analysis was performed using SPSS version 20 (SPSS, Inc, Chicago, IL). Results are presented as mean ± SD or as percentages. P values < .05 were considered statistically significant. Univariate Pearson’s correlation was used to analyze the relation between two parametric variables. Differences between the groups for the baseline characteristics and

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echocardiographics measurements were calculated using t tests for differences in means

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4.RESULTS

4.1 POPULATION CHARACTERISTICS

The study protocol is summarized in Figure 4.1.

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The subjects were middle age adults with a mean age was 53 ± 13 years and 64% were women. The mean BMI was 26 ± 5 and 85% of subjects were caucasian. The average heart rate was 74 ± 12; systolic and diastolic blood pressure were 127 ± 16 and 71 ± 10 mmHg respectively. Overall, 32% were hypertensive, 14% had high cholesterol values and family history of cardiac diseases, 8% were current smokers, 2% had diabetes. Distribution of the cardiovascular risk factors are illustrated in Figure 4.2.

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About cardiovascular drugs taken by the patients at the time of the study we observed 10% of patients on calcium channel blockers, 9% on β-blockers, 9% on statins, 8% on angiotensin converting enzyme inhibitors (ACE-i) or angiotensin receptor blockers (ARB) therapy and 8% on aspirin.

Regarding the type of cancer 40% of the subjects were affected by breast cancer, followed by 16% with thyroid cancer, 9% with melanoma, 8% with gastro-intestinal cancer. The remaining 27% were constituted by others type of cancer (including sarcoma, kidney cancer and ovarian cancer) as shown in Figure 4.3.

Exposure to cancer drugs included herceptin in 17 patients (32%), anthracyclines in 13 patients (24%), followed by tyrosine kinase inhibitors and alkaloid plants in 12 patients (23%). Less than 10% of patients had exposure to cisplatin, fluorouracil and alkylating agents.

4.2 CONVENTIONAL ECHOCARDIOGRAPHY AND ECG

Standard 2D echocardiographic measurements were substantially normal. Mean LVEF was 63 ± 5%, left ventricular mass index (LVMI) was 74 ± 20 g/m2_{, average EDV and} ESV were 102 ± 20 and 38 ± 15 ml. Septal S’ values were 8 ± 2 while lateral S’ was 9 ± 2. Diastolic findings included E/A ratio 1.1 ± 0.45, E/E’ medial and E/E’ lateral were respectively 10 ± 3.2 and 7 ± 2.1. Right ventricular function was assessed in terms of TAPSE whose mean value was 22 ± 4 mm, S’ velocity (with average value of 12 ± 2.5 cm7sec) and mean PASP of 27 ± 7 mmHg.

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Basal ECG showed normal findings in all patients except for one with prolonged QTc and one with I degree AV block.

Baseline clinical and echocardiographic characteristic of the cancer patients group are shown in Table 4.1.

Figure 4.3. Type of cancer in the study group.

4.3 3D ECHOCARDIOGRAPHY

Three-dimensional echocardiography performed in 20 subjects showed a mean LVEF of 60 ± 9%, mean EDV of 95 ± 24 ml and ESV of 39 ± 16 ml. Very good correlation was found between 2D and 3D LVEF (r=0.8).

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4.4 SPECKLE TRACKING ECHOCARDIOGRAPHY

Two-dimensional speckle tracking echocardiography showed mean GLS values of -19.8 ± 3.3 % mean GCS of -23.4 ± 4.8% and mean GRS of 29.7 ± 14%. Three-dimensional speckle tracking echocardiography performed in a subgroup of 20 patients revealed mean GLS of -21 ± 4%, mean GCS -31 ± 4% and mean GRS of 42.7 ± 5.4%.

4.5 MAGNETIC RESONANCE IMAGING

Magnetic resonance imaging was carried out in 81% of the population study (n=43) and showed fibrosis/loss of torsion in 10 patients (23%) with no correlation with strain values. Mean LVEF assessed by CMR was 65 ± 6%. Good correlation between the LVEF assessed by 2D echocardiography and CMR resulted from our study (r=0.8).

4.6 BIOMARKERS

Troponin I was altered in one patient while BNP was increased in 34% of the patients and significantly increased (values >50 pg/ml) in 15 subjects (28%).

4.7 REPRODUCIBILITY

Reproducibility was carried out in 20 randomly selected patients. One hundred and twenty two-dimensional images were obtained in apical four, two and three-chamber and basal, mid-cavity and apical short axis views. Values of peak systolic strain of these images of the LV were used for statistical analysis. Segments were analysed by the same operator

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after 2 weeks since the first analysis (for intraobserver reproducibility) and by two different readers (for interobserver reproducibility).

Table 4.1. Baseline clinical and echocardiographic characteristics of cancer patients.

The intraobserver variability showed good correlation for both GLS and GCS (ICC 0.8; r= 0.7) and moderate correlation for GRS (ICC 0.7; r= 0.6).

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The interobserver reproducibility of global strain measures was moderate for GLS, GCS and GRS (ICC 0.7; r= 0.5).

Reproducibility results are shown in detail in Table 4.2 and 4.3.

Figure 4.4. GLS and GRS curves in a cancer patient with normal LVEF.

4.8 CONTROLS GROUP

We selected a cohort of 25 controls from our echo-laboratory. They were age and sex matched with cancer patients. Mean age was 49 ± 14 years, 60% were women and the mean BMI was 27 ± 5. Mean SBP and DBP were respectively 125 ± 14 and 72 ± 12

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mmHg. Mean HR was 71 ± 15 bpm. Hypertension was observed in 30% of the subjects while 13% had high cholesterol, 7% were smokers and 1% was diabetic.

We performed conventional 2D echocardiography and 2D speckle tracking echocardiography.

Clinical and echocardiographic characteristics of controls are shown in Table 4.4 and demonstrates normal LVEF, substantially normal diastolic findings and normal right ventricle assessment.

Strain measurements showed global longitudinal strain of -22 ± 2%, global circumferential strain of -29.5 ± 5% and global radial strain of 42 ± 10%.

We compared the strain measurements in the cancer patients group and in the controls group using the Student t test . Results and P values are summarized in Table 4.4.

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Table 4.2. Intra-observer reproducibility of strain measurements.

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Table 4.4. Baseline clinical and echocardiographic characteristics of controls.

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5. DISCUSSION

Cancer patients or cancer survivors are an increasing population worldwide and cancer drugs can widely affect the cardiovascular system and the myocardial function. LVEF is the most common used parameter to evaluate patients before, during and after the chemotherapy but it can fail to detect subclinical cardiac dysfunction.

Speckle tracking echocardiography has been used to identify subclinical dysfunction in a variety of diseases. Many studies in literature have demonstrated strain imaging can be an useful tool in cancer patients who still present normal systolic function assessed in terms of ejection fraction.

In the present study we focused our attention on 53 middle age adult cancer patients exposed to cancer drug therapy with normal LVEF (≥55%), as stated by the EAE/ASE recommendations. Despite normal systolic function and roughly normal conventional echo parameters (including diastolic findings) we found low-normal values for global longitudinal and circumferential strain and significantly lower radial strain values when compared to published meta-analysis data. To strengthen our results we selected a cohort of 25 patients from our echo-laboratory, with LVEF≥55%. They were age and sex-matched (compared with cancer patients) with the same pattern of cardiovascular risk

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factors. In this cohort we performed 2D speckle tracking analysis using the same software in order to assess global systolic longitudinal, circumferential and radial strain. We discovered significant differences in terms of GLS, GCS and GRS values (p<.000) between the two groups.

Cardiac magnetic resonance, performed in 81% of the cancer patients, showed evidence of fibrosis and/or loss of torsion only in 10 patients without any correlation with strain values.

Our findings support the published data regarding a more sensitive detection of cardiac dysfunction through strain parameters. We decided to use strain instead and we did not considered strain rate because of its higher variability.

Regarding the accurate imaging modality of the cardiac magnetic resonance in the context of cancer-related cardiac toxicity and still normal LVEF our results seem to provide evidence CMR could fail in identifying early structural alteration (such as fibrosis) in this context.. We can assume such structural changes may occur later, perhaps months after the cancer drug exposure.

That which seems to occur more precociously is instead the functional damage that may be well detected by speckle tracking echocardiography, also in patient with normal ejection fraction. This supports the limits of the ejection fraction as the only echocardiographic parameter to rely on.

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In terms of role of bio-markers our findings do not support the importance of Troponin I that was altered only in one patient, without any correlation with strain indices while worthy of attention seems to be BNP. Blood levels of brain natriuretic peptide showed a significant increase in almost on third of the cancer patients (28%) when considering the cut-off of 50 ng/ml as a clinically increased value.

Interestingly all the patients with abnormal BNP had also alterations in cardiac magnetic resonance.

Especially in these complex patients it seems of paramount importance an integrated clinical and strumental approach where, beside the conventional systolic and diastolic parameters, we consider strain values and biomarkers (especially BNP). The information given by those complementary parameters could identify a subset of patients with more pronounced myocardial damage or more compromised clinical pattern and increased risk to develop cardiotoxicity.

Analyzing the technical and much discussed aspects of the strain imaging and its lability in our study the intra and interobserver reproducibility values of the deformation indices appear to be reliable when performed by expert readers and can thus enter in routine clinical practice. If applied on good quality images the technique is less time consuming and gives reproducible values.

Our cardio-oncological patients not exposed to cancer drugs entered thus a follow-up data-base to analyze the strain values over time and the possible role of the cancer itself

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on myocardial deformation indices. Several studies have reported altered metabolism as well as increased protein loss in hearts of patients and mice with cancer cachexia. Studies carried out in mice models with cancer cachexia have shown a decrease in myocardiocytes contractile function (related to protein oxidation and alteration of myosin chain), despite a preserved ejection fraction. It would be interesting to confirm the these data in humans with cancer and assess a possible role of the tumor growth on the human heart .

There are limitations to the present study. First of all the variety of tumors and cancer drugs in the population and the large number of patients excluded due to concurrent pathologies. Another limitation includes our study does not provide baseline strain values before the exposure to cancer drugs and the possibility to have strain values during the follow up (for example at 6 months and 1 year after the exposure). Finally we used 2D LVEF in all the subjects and we performed 3D only in 20 of them but 3D LVEF would be the best parameter and may also be used in further studies to quantify the left ventricular systolic function.

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6. CONCLUSIONS

Cancer patients and cancer survivors are a booming population all over the world and in the last years increasing attention has been devoted on cardiac side effects of cancer therapeutics and potential strategies to early detect and treat them. Due to the increasing variety of cancer drugs it is mandatory to carefully monitor the cardiac function of these patients. New strategies for early detection of subclinical myocardial dysfunction are required and strain imaging has proved capable of detecting early alteration of cardiac function.

In our study global systolic longitudinal, circumferential and radial strain showed significantly lower values, despite preserved ejection fraction, in cancer patient with exposure to cancer drugs. According to our findings, cancer patients could present sub-clinical myocardial dysfunction affecting all the myocardial layers, in particular the mid-wall myocardium. This could be the result of the functional damage induced by cancer therapeutics that we are not able to quantify using conventional parameters such as the ejection fraction nor more advanced imaging technique (as CMR).

This study provides evidence deformation indices could represent a valid method to identify early cardiac dysfunction in “apparently non-dysfunctional” patients. However it

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is important an integrated approach that include the evaluation of conventional echo parameters together with biomarkers and magnetic resonance imaging.

Further studies, involving larger numbers and longer term follow up, are needed to support our hypothesis and better understand the clinical impact of our conclusions.

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