Cardiotoxicity Induced by Protein Kinase Inhibitors in Patients with Cancer

Cancer therapy in patients with reduced kidney function

Chronic kidney disease (CKD) and cancer constitute two major public health burdens, and both are on the rise. Moreover, the number of patients affected simultaneously by both conditions is growing. The potential nephrotoxic effect of cancer therapies is particularly important for patients with CKD, as they are also affected by several comorbidities. Therefore, administering the right therapy at the right dose for patients with decreased kidney function can represent a daunting challenge. We review in detail the renal toxicities of anticancer therapies, i.e. conventional chemotherapy, targeted therapy, immune checkpoint inhibitors and radioligand therapies, issue recommendations for patient monitoring along with guidance on when to withdraw treatment and suggest dosage guidelines for select agents in advanced stage CKD. Various electrolytes disturbances can occur as the result of the administration of anticancer agents in the patient with decreased kidney function. These patients are prone to developing hyponatremia, hyperkalemia and other metabolic abnormalities because of a decreased glomerular filtration rate. Therefore, all electrolytes, minerals and acid base status should be checked at baseline and before each administration of chemotherapeutic agents. Moreover, studies on patients on kidney replacement therapy are very limited and only single cases or small case series have been published. Therefore, clinical therapeutical decisions in cancer patients with decreased function should be made by multidisciplinary teams constituted of medical oncologists, nephrologists and other specialists. Onconephrology is an evolving and expanding subspecialty. It is crucial to consider anticancer drug treatment in these patients and offer them a chance to be treated effectively.

A fatal case of cabozantinib-induced cardiomyopathy

Cabozantinib, a multi-kinase receptor inhibitor, is utilized in the treatment of advanced malignancies such as metastatic renal cancers. While rare, cabozantinib-induced cardiotoxicity has emerged as a recognized adverse effect with potentially reversible outcomes. We report the case of a 55-year-old male who developed fatal cardiomyopathy 4 months after initiating cabozantinib therapy. Despite its rarity, cardiomyopathy after initiation of cabozantinib can be lethal if not diagnosed early. This case underscores a significant gap in the surveillance of patients treated with newer agents like cabozantinib. Larger observational studies are needed to assess the prevalence and impact of cardiomyopathy after initiation of cabozantinib therapy, and to determine the cost-effectiveness of early surveillance protocols.

Sorafenib reduces the production of epoxyeicosatrienoic acids and leads to cardiac injury by inhibiting CYP2J in rats

Sorafenib, an important cancer drug in clinical practice, has caused heart problems such as hypertension, myocardial infarction, and thrombosis. Although some mechanisms of sorafenib-induced cardiotoxicity have been proposed, there is still more research needed to reach a well-established definition of the causes of cardiotoxicity of sorafenib. In this report, we demonstrate that sorafenib is a potent inhibitor of the CYP2J enzyme. Sorafenib significantly inhibited the production of epoxyeicosatrienoic acids (EETs) in rat cardiac microsomes. The in vivo experimental results also showed that after the administration of sorafenib, the levels of 11,12-EET and 14,15-EET in rat plasma were significantly reduced, which was similar to the results of CYP2J gene knockout. Sorafenib decreased the levels of EETs, leading to abnormal expression of mitochondrial fusion and fission factors in heart tissue. In addition, the expression of mitochondrial energy metabolism factors (Pgc-1α, Pgc-1β, Ampk, and Sirt1) and cardiac mechanism factors (Scn5a and Prkag2) was significantly reduced, increasing the risk of arrhythmia and heart failure. Meanwhile, the increase in injury markers Anp, CK, and CK-MB further confirmed the cardiotoxicity of sorafenib. This study is of great significance for understanding the cardiotoxicity of sorafenib, and is also a model for studying the cardiotoxicity of other drugs that inhibit CYP2J activity.

Cancer Therapies and Cardiomyocyte Viability: Which Drugs are Directly Cardiotoxic?

BACKGROUND

Increased cancer survivorship represents a remarkable achievement for modern medicine. Unfortunately, cancer treatments have inadvertently contributed to cardiovascular (CV) damage, significantly threatening the health and quality of life of patients living with, through and beyond cancer. Without understanding the mechanisms, including whether the cardiotoxicity is due to the direct or indirect effects on cardiomyocytes, prevention and management of cardiotoxicity can pose challenges in many patients. To date, the cardiotoxicity profiles of most of the chemotherapy drugs are still poorly understood.

AIM

To conduct a pilot study to investigate the direct effects of a range of cancer therapies on cardiomyocyte viability.

METHODS

Primary human cardiomyocytes (HCM) were cultured and seeded into 96-well culture plates. A total of 35 different Food and Drug Administration-approved anti-cancer drugs were added to the HCM cells with a concentration of 1uM for 72 hours. The viability of HCMs was determined using CellTitre-Glo. The experiments were repeated at least three times for each drug with HCMs of different passages.

RESULTS

We identified 15 anti-cancer agents that significantly reduced HCM viability. These drugs were: (1) anthracyclines (daunorubicin [HCM viability, mean %±standard error, 13.7±3.2%], epirubicin [47.6±5.3%]), (2) antimetabolite (azacitidine [67.1±2.4%]), (3) taxanes (paclitaxel [60.2±3.0%]), (4) protein kinase inhibitors (lapatinib [49.8±7.0%], ponatinib [42.4±9.0%], pemigatinib [68.1±2.3%], sorafenib [52.9±10.6%], nilotinib [64.4±4.5%], dasatinib [38.5±3.6%]), (5) proteasome inhibitors (ixazomib citrate [65.4±7.2%]), (6) non-selective histone-deacetylase inhibitor (panobinostat [19.1±4.1%]), poly adenosine diphosphate-ribose polymerase inhibitor (olaparib [68.2±1.7%]) and (7) vinca alkaloids (vincristine [44.6±7.4%], vinblastine [31.2±3.9%]).

CONCLUSIONS

In total, 15 of the 35 commercially available anti-cancer drugs have direct cardiotoxic effects on HCM. Some of those, have not been associated with clinical cardiotoxicity, while others, known to be cardiotoxic do not appear to mediate it via direct effects on cardiomyocytes. More detailed investigations of the effects of cancer therapies on various cardiovascular cells should be performed to comprehensively determine the mechanisms of cardiotoxicity.

Clinical evidence and adverse event management update of patients with RET- rearranged advanced non-small-cell lung cancer (NSCLC) treated with pralsetinib

Current non-small cell lung cancer (NSCLC) management relies on genome-driven precision oncology thus shifting treatment paradigm towards biomarker-guided tumor-agnostic approaches. Recently, rearranged during transfection (RET) has been endorsed as tissue-agnostic target with sensitivity to RET inhibition. There are currently two selective RET tyrosine kinase inhibitors, pralsetinib and selpercatinib. The recent introduction of pralsetinib in the treatment algorithm of RET-rearranged tumor along with the mounting clinical evidence of pralsetinib durable activity from both randomized and observational studies holds the potential to disclose new avenues in the management of RET fusion positive NSCLC patients. Our narrative review aims to discuss the available clinical evidence on pralsetinib efficacy, particularly on brain metastases, and tolerability profile. In addition, our work explores the relevance of detecting RET fusions upfront in the disease history of patients with NSCLC.

Cardiomyocyte intercellular signalling increases oxidative stress and reprograms the global- and phospho-proteome of cardiac fibroblasts

Pathological reprogramming of cardiomyocyte and fibroblast proteome landscapes drive the initiation and progression of cardiac fibrosis. Although the secretome of dysfunctional cardiomyocytes is emerging as an important driver of pathological fibroblast reprogramming, our understanding of the downstream molecular players remains limited. Here, we show that cardiac fibroblast activation (αSMA+) and oxidative stress mediated by the secretome of TGFβ-stimulated cardiomyocytes is associated with a profound reprogramming of their proteome and phosphoproteome landscape. Within the fibroblast global proteome there was a striking dysregulation of proteins implicated in extracellular matrix, protein localisation/metabolism, KEAP1-NFE2L2 pathway, lysosomes, carbohydrate metabolism, and transcriptional regulation. Kinase substrate enrichment analysis of phosphopeptides revealed potential role of kinases (CK2, CDK2, PKC, GSK3B) during this remodelling. We verified upregulated activity of casein kinase 2 (CK2) in secretome-treated fibroblasts, and pharmacological CK2 inhibitor TBB (4,5,6,7-Tetrabromobenzotriazole) significantly abrogated fibroblast activation and oxidative stress. Our data provides molecular insights into cardiomyocyte to cardiac fibroblast crosstalk, and the potential role of CK2 in regulating cardiac fibroblast activation and oxidative stress.

Cardiac safety profile of type II kinase inhibitors: Analysis of post-marketing reports from databases of European Medicine Agency & World Health Organization

BACKGROUND

Targeted therapy with type II kinase inhibitors (KIs) is one of the preferred choices in cancer treatment. However, type II KI therapy can be associated to serious cardiac risks.

OBJECTIVES

This study aimed to assess the occurrence of cardiac events reported with type II KIs in Eudravigilance (EV) and VigiAccess databases.

METHODS

To evaluate reporting frequency of individual case safety reports (ICSRs) related to cardiac events, we referred EV and VigiAccess databases. The data was retrieved for the period from date of marketing authorization of respective type II KI till 30 July 2022. Computational analysis was conducted with data from EV and VigiAccess using reporting odds ratio (ROR) along with its 95% confidence interval (CI) under Microsoft excel.

RESULTS

In total, 14429 ICSRs in EV and 11522 ICSRs from VigiAccess were retrieved concerning cardiac events with at least one type II KI as the suspected drug. In both databases, most of the ICSRs were reported for Imatinib, Nilotinib, and Sunitinib, while most reported cardiac events were myocardial infarction/acute myocardial infarction, cardiac failure/congestive heart failure and atrial fibrillation. As per EV, 98.8% ICSRs with cardiac ADRs were assessed as serious and of which, 17.4% ICSRs were associated with fatal outcomes and approximately 47% included patient's recovery as a favorable outcome. Nilotinib (ROR 2.87, 95% CI 3.01-2.74) and Nintedanib (ROR 2.17, 95% CI 2.3-2.04) were associated with a significant increase in reporting frequency of ICSRs related to cardiac events.

CONCLUSIONS

Type II KI related cardiac events were serious and associated with unfavorable outcomes. A significant increase in ICSRs reporting frequency was observed with Nilotinib and Nintedanib. These results insist for a consideration of revision of cardiac safety profile of Nilotinib and Nintedanib, specifically for risks of myocardial infarction and atrial fibrillation. Additionally, the need for other ad-hoc studies is indicated.

CDK4/6 inhibitors: basics, pros, and major cons in breast cancer treatment with specific regard to cardiotoxicity - a narrative review

Breast cancer is characterized by the uncontrolled proliferation of breast cells, with a high incidence reported in 2020 to have affected over 2 million women. In recent years, the conventional methods of treating breast cancer have involved radiotherapy and chemotherapy. However, the emergence of CDK4/6 inhibitors has shown potential as a promising cancer therapy. Cyclin-dependent kinases (CDK) inhibitors are a class of molecules that impede the formation of an active kinase complex, thereby hindering its activity and consequently halting the progression of the cell cycle. It was discovered that they have a significant impact on impeding the progression of the cancer. This is evident with the Food and Drug Administration's approval of drugs such as palbociclib, ribociclib, and abemaciclib for hormone receptor-positive metastatic breast cancer in combination with specific endocrine therapies. In spite of enormous success in breast cancer treatment, certain obstacles have emerged, such as therapy resistance, side effects, and most of all, cardiotoxicity. Some of these drawbacks have been successfully overcome by dosage reduction, different combinations of the drugs, and the assessment of each patient's condition and suitability prior to treatment. Yet other drawbacks still require tenacious research, especially certain cases of cardiotoxicities. This article delves into the biological mechanisms of CDK4/6 in the cell cycle and cancer, as well as the clinical advantages and most common adverse events (AEs) associated with CDK4/6 inhibitors. The primary objective of this review is to provide a comprehensive analysis of cardiotoxic AEs and elucidate the underlying pathophysiological mechanisms responsible for the cardiotoxicity of CDK4/6 inhibitors.

Recent Perspectives on Cardiovascular Toxicity Associated with Colorectal Cancer Drug Therapy

Cardiotoxicity is a well-known adverse effect of cancer-related therapy that has a significant influence on patient outcomes and quality of life. The use of antineoplastic drugs to treat colorectal cancers (CRCs) is associated with a number of undesirable side effects including cardiac complications. For both sexes, CRC ranks second and accounts for four out of every ten cancer deaths. According to the reports, almost 39% of patients with colorectal cancer who underwent first-line chemotherapy suffered cardiovascular impairment. Although 5-fluorouracil is still the backbone of chemotherapy regimen for colorectal, gastric, and breast cancers, cardiotoxicity caused by 5-fluorouracil might affect anywhere from 1.5% to 18% of patients. The precise mechanisms underlying cardiotoxicity associated with CRC treatment are complex and may involve the modulation of various signaling pathways crucial for maintaining cardiac health including TKI ErbB2 or NRG-1, VEGF, PDGF, BRAF/Ras/Raf/MEK/ERK, and the PI3/ERK/AMPK/mTOR pathway, resulting in oxidative stress, mitochondrial dysfunction, inflammation, and apoptosis, ultimately damaging cardiac tissue. Thus, the identification and management of cardiotoxicity associated with CRC drug therapy while minimizing the negative impact have become increasingly important. The purpose of this review is to catalog the potential cardiotoxicities caused by anticancer drugs and targeted therapy used to treat colorectal cancer as well as strategies focused on early diagnosing, prevention, and treatment of cardiotoxicity associated with anticancer drugs used in CRC therapy.

Medication guide for dose adjustment and management of cardiotoxicity and lipid metabolic adverse events of oral antineoplastic therapy

Objective

The management of cardiotoxicity concerning the use of oral antineoplastic agents (OAAs) is a challenge for healthcare professionals. Our objective was to create a comprehensive medication management guide with dose adjustment recommendations on OAAs concerning cardiotoxic and lipid metabolic adverse events (AEs) to assist healthcare professionals when prescribing OAAs.

Materials and methods

A review of the available information on all dose adjustments necessary to safely prescribe and dispense OAAs concerning cardiotoxicity was conducted. In January 2023, we identified all OAAs authorized by the European Medicines Agency (EMA). For each drug, the latest summary of product characteristics (SPC) approved by the EMA and the tertiary data source Lexicomp® were reviewed. Cardiotoxic AEs were recorded, namely, QT interval prolongation, decrease in left ventricular ejection fraction (LVEF), imbalances in blood pressure (hypertension and hypotension), alterations in heart rate (tachycardia and bradycardia), and thrombosis. Any available dose adjustment recommendations in case of an occurrence of these adverse events were collected.

Results

In all, 93 different OAAs had been approved by the EMA and were reviewed. Among them, 51.6% have recognized cardiotoxic AEs and 10.8% can cause alterations in lipid metabolism. A total of 27 (29.0%) OAAs had specific recommendations regarding QT prolongation; 88.9% were listed in the SPC and 59.3% in Lexicomp®. Eight OAAs (9.68%) have reported a decrease in LVEF, and four of these drugs, namely, encorafenib, lorlatinib, ripretinib, and sunitinib, have specific management recommendations. Almost half (49.5%) of currently approved OAAs can potentially alter blood pressure; 34 (36.6%) of them have been reported to cause hypertension and 12 (12.9%) are related to hypotension. Tachycardia and/or bradycardia are associated with 22.6% and 8.6% of the evaluated drugs, respectively. Regarding thrombosis, 30 (32.3%) of the drugs analyzed included the appearance of a thrombus as a possible AE.

Conclusions

More than half of the OAAs can produce cardiotoxic effects, with the most frequent being blood pressure alteration and QT interval prolongation with a non-depreciable incidence of LV dysfunction or thrombosis. Before starting the treatment, it is necessary to stratify baseline cardiovascular risk, plan a surveillance schedule, and consider referral to cardio-oncology units.

A practical guide to managing cardiopulmonary toxicities of tyrosine kinase inhibitors in chronic myeloid leukemia

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) but their use was associated with a range of serious cardiopulmonary toxicities including vascular adverse events, QT prolongation, heart failure, pleural effusion, and pulmonary arterial hypertension. Dedicated clinical management guidelines for TKI-induced toxicities are not available. This review aims to discuss TKI-associated cardiopulmonary toxicities and proposes a practical guide for their management.

Incidence of heart failure following exposure to a protein kinase inhibitor, a French population-based study

AIMS

Pharmacovigilance signals of heart failure (HF) following exposure to protein kinase inhibitors (PKIs) have been detected in recent years. Our aim was to identify the PKIs most frequently associated with the development of HF.

METHODS

Using the French National Healthcare Database, all patients newly exposed to a PKI between January 2011 and June 2014 were followed up for 18 months. Specific hospitalization diagnosis and long-term HF-related disease codes were used to identify HF patients. HF incidence rate ratios (IRRs) were measured and adjusted hazard ratios (aHRs) were estimated using a Cox model. Sensitivity analyses were performed to limit the potential indication and competitive risk bias.

RESULTS

Thirteen PKIs were studied. Among the 49 714 new PKI users registered during the study period, the mean IRR of HF was 3.38 per 100 person-years, with a median time to onset of 155 days. We found a significant increase in the incidence of HF for six medicinal products: pazopanib (aHR = 2.42, 95% confidence interval [CI] 1.67-3.52), dasatinib (aHR = 2.22, 95% CI 1.42-3.44), ruxolitinib (aHR = 2.11, 95% CI 1.69-2.64), crizotinib (aHR = 1.71, 95% CI 1.07-2.72), everolimus (aHR = 1.45, 95% CI 1.26-1.67) and vemurafenib (aHR = 1.37, 95% CI 1.01-1.86). Sensitivity analyses were consistent with our primary analysis.

CONCLUSIONS

The current study provides knowledge on HF following exposure to a PKI. Additional studies could confirm these results for dasatinib, everolimus, pazopanib and ruxolitinib, and particularly for the two medicinal products with results slightly above the significance threshold, namely, crizotinib and vemurafenib, in our sensitivity analyses.

Coronary atherosclerosis and chemotherapy: From bench to bedside

Cardiovascular disease, particularly coronary artery disease, is the leading cause of death in humans worldwide. Coronary heart disease caused by chemotherapy affects the prognosis and survival of patients with tumors. The most effective chemotherapeutic drugs for cancer include proteasome inhibitors, tyrosine kinase inhibitors, immune checkpoint inhibitors, 5-fluorouracil, and anthracyclines. Animal models and clinical trials have consistently shown that chemotherapy is closely associated with coronary events and can cause serious adverse cardiovascular events. Adverse cardiovascular events after chemotherapy can affect the clinical outcome, treatment, and prognosis of patients with tumors. In recent years, with the development of new chemotherapeutic drugs, new discoveries have been made about the effects of drugs used for chemotherapy on cardiovascular disease and its related mechanisms, such as inflammation. This review article summarizes the effects of chemotherapeutic drugs on coronary artery disease and its related mechanisms to guide efforts in reducing cardiovascular adverse events during tumor chemotherapy, preventing the development of coronary heart disease, and designing new prevention and treatment strategies for cardiotoxicity caused by clinical tumor chemotherapy.

Association between thyroid cancer and cardiovascular disease: A meta-analysis

Objective

To determine the association between thyroid cancer and coronary artery disease, atrial fibrillation, cerebrovascular disease, and cardiovascular disease mortality.

Methods

The PubMed, Embase, and Cochrane Library databases were searched for eligible studies from inception to September 22, 2022. Keywords included "thyroid cancer", "atrial fibrillation", "coronary artery disease", "cerebrovascular disease", and "mortality". Primary outcomes included the incidence of coronary artery disease, cerebrovascular disease, atrial fibrillation, and cardiovascular disease mortality among patients with thyroid cancer. Secondary outcomes included cardiovascular disease events among those with thyroid cancer that received or did not receive radioactive iodine or lenvatinib. Estimates were pooled using fixed- and random-effects meta-analysis.

Results

A total of 771,220 patients who underwent thyroidectomy in 15 studies were included. Risk for cerebrovascular disease (risk ratio [RR] 1.15 [95% confidence interval (CI) 1.10-1.21]) and atrial fibrillation [RR 1.59 (95% CI: 1.45-1.73)] were significantly increased. Risk for coronary artery disease was significantly increased [RR 1.12 (95% CI: 1.08-1.17)] in the common effect model. Cardiovascular disease mortality associated with thyroid cancer was not significant [RR 0.93 (95% CI: 0.59-1.45)]. Radioactive iodine had a neutral effect on cardiovascular disease [RR 1.00 (95% CI: 0.87-1.16)], and there was no beneficial nor harmful effect among different RAI doses.

Conclusions

Thyroid cancer was significantly associated with a higher risk for cerebrovascular disease and atrial fibrillation; however, the hazard risk was not different between patients with and without radioactive iodine treatment. Thyroid cancer treatment should be individualized considering the potential harms and benefits to cardiovascular health.

Early Diagnosis of Chemotherapy-Linked Cardiotoxicity in Breast Cancer Patients Using Conventional Biomarker Panel: A Prospective Study Protocol

The prognosis of cancer treatment depends on, among other aspects, the cardiotoxicity of chemotherapy. This research aims to create a feasible algorithm for the early diagnosis of antitumor therapy cardiotoxicity in breast cancer patients. The paper represents a protocol for a prospective cohort study with N 120 eligible participants admitted for treatment with anthracyclines and/or trastuzumab. These patients will be allocated into four risk groups regarding potential cardiotoxic complications. Patients will be examined five times every three months for six biomarkers,: cardiac troponin I (cTnI), brain natriuretic peptide (BNP), C-reactive protein (CRP), myeloperoxidase (MPO), galectin-3 (Gal-3), and D-dimer, simultaneously with echocardiographic methods, including speckle tracking. The adjusted relative risk (aOR) of interrupting an entire course of chemotherapy due to cardiotoxic events will be assessed using multiple analyses of proportional Cox risks. The Cox model will also assess associations between baseline biomarker values and time to cardiotoxic events. Moreover, partly conditional survival models will be applied to determine associations between repeated assessments of changes in biomarkers from baseline and time to cancer therapy-related cardiac dysfunction. All models will be adjusted for cancer therapy regimen, baseline LVEF, groups at risk, baseline biomarker values, and age. The decision-tree and principal component analysis (PCA) methods will also be applied. Thus, feasible patterns will be detected.

Lazertinib: on the Way to Its Throne

Lazertinib is an oral, irreversible, third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that forms an irreversible covalent bond to the Cys797 residue in the ATP-binding site of the EGFR kinase domain and exhibits a high selectivity for sensitizing and T790M EGFR mutations. In January 2021, it was first approved for the treatment of advanced or metastatic non-small cell lung cancer (NSCLC) patients with EGFR T790M who had previously received EGFR TKI therapy based on LASER201, a phase I/II trial. At a recommended dose of 240 mg, lazertinib achieved an encouraging anti-tumor activity in both extra- and intracranial lesions. With a high half-maximal inhibitory concentration for EGFR wildtype tumors, it is anticipated to pose a lower risk of skin and cardiac adverse events compared to osimertinib. Lazertinib is currently being investigated as a monotherapy in first-line treatment and in combination with amivantamab under various settings. In this review, we systematically summarize the preclinical and clinical data of lazertinib and discuss future perspectives on the treatment of EGFR-mutant NSCLC.

Biomarkers of Trastuzumab-Induced Cardiac Toxicity in HER2- Positive Breast Cancer Patient Population

Simple Summary

Trastuzumab administered as a (neo)adjuvant therapy in radically treated Human Epidermal Growth Factor Receptor 2 (HER2)-positive breast cancer patients improves overall survival. This study aimed to assess if factors commonly thought to play a role as biomarkers of trastuzumab-induced cardiotoxicity (TIC) are pathognomonic for this injury. Data obtained for 130 HER2-positive breast cancer patients do not support an influence of N-terminal brain natriuretic peptide (NT-proBNP), creatine kinase-MB (CK-MB), or myoglobin on the frequency of TIC. Suggestions for trastuzumab therapy include: close cooperation between cardiologists and oncologists; not using NT-proBNP, CK-MB, or myoglobin as standard TIC predictive markers; organizing prospective studies assessing the role of these parameters as TIC predictive markers in the case of HER2 blockage in conjunction with doublet immunotherapy or other anti-HER2 agents.

Abstract

Trastuzumab-induced cardiotoxicity (TIC) can lead to early treatment discontinuation. The aim of this study was to evaluate: N-terminal brain natriuretic peptide (NT-proBNP), creatine kinase-MB (CK-MB), myoglobin, and selected biochemical and clinical factors as predictors of TIC. One hundred and thirty patients with HER2-positive BC receiving adjuvant trastuzumab therapy (TT) were enrolled. Measurement of cardiac markers and biochemical tests as well as echocardiography were performed prior to TT initiation and every three months thereafter. Cardiotoxicity leading to treatment interruption occurred in 24 patients (18.5%). While cardiotoxicity caused early treatment discontinuation in 14 patients (10.8%), the TIC resolved in 10 (7.7%) and TT was resumed. The most common complication was a decrease in left ventricular ejection fraction of more than 10% from baseline or below 50% (7.7%). In patients with TIC, there was no increase in the levels of NT-proBNP, myoglobin, and CK-MB. BMI, hypertension, ischemic heart disease, diabetes, age, cancer stage, type of surgery, use of radiotherapy, chemotherapy, and hormone therapy were shown to not have an effect on TIC occurrence. NT-proBNP, myoglobin, and CK-MB are not predictors of TIC. There is an ongoing need to identify biomarkers for TIC.