Cardiac Biomarkers and Electrocardiographic Changes in Women with Breast Cancer Undergoing Chemotherapy: A Prospective Study

All articles of this category (opens in new window) Address for correspondence Luís Carlos Lopes-Júnior (lopesjr.lc@gmail.com) Background: Chemotherapy-induced cardiotoxicity (CIC) affects treatment adherence and quality of life in breast cancer (BC) patients. Troponin I, C-reactive protein (CRP), and electrocardiographic (ECG) changes assist in the early detection of cardiovascular risk. QTc prolongation, arrhythmias, and elevated troponin I levels have been associated with increased risk of cardiovascular events in oncology patients. Understanding the cardiac effects of chemotherapy is essential to improve diagnosis, management, and clinical outcomes. Objective: To evaluate the evolution of cardiac biomarkers and ECG alterations at two time points (T1 and T6) in breast cancer patients undergoing six cycles of chemotherapy. Methods: This prospective study (2022–2024) was conducted at an oncology referral center in Brazil and included 50 women with BC (stage I–III) undergoing outpatient chemotherapy. Cardiac biomarkers (troponin I, CRP) and ECG parameters were assessed before chemotherapy (T1) and after six cycles (T6). Evaluated variables included heart rhythm, heart rate (HR), QTc interval, T-wave abnormalities, atrioventricular (AV) blocks, and atrial fibrillation (AF). Statistical analyses were performed using McNemar and Wilcoxon signed-rank tests in Stata 17. Results: Fifty BC patients (mean age: 53.3 ± 11.4 years) were included, with equal distribution between ductal carcinoma in situ and invasive ductal carcinoma (50% each). Most were stage II (62%); 42% received neoadjuvant and 58% adjuvant chemotherapy. The prevalence of arrhythmias increased from 4.35% (T1) to 13.04% (T6), although HR remained stable in 93.48% of patients. QTc prolongation doubled from 13.04% (T1) to 26.09% (T6) (p < 0.001), suggesting increased arrhythmic risk. Troponin I levels rose significantly (p < 0.001) from 2.22 ± 4.05 ng/mL (T1) to 11.43 ± 25.91 ng/mL (T6), with a peak of 126.1 ng/mL, indicating progressive myocardial injury. CRP levels also increased (from 3.25 ± 3.56 mg/L to 5.69 ± 11.56 mg/L), but this change was not statistically significant (p = 0.238). Conclusion: BC patients undergoing chemotherapy showed significant increases in troponin I and QTc prolongation, indicating heightened risk of CIC. The rise in arrhythmias and ECG abnormalities highlights the need for continuous cardiac monitoring and early cardioprotective interventions. Routine cardiology evaluation may improve outcomes and reduce complications. Further research is warranted to optimize cardiac surveillance in oncology patients. Publication History Article published online: 26 June 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil Bibliographical Record Naira Santos D’Agostini, Karoline Neumann, Luiz Claudio Barreto Silva Neto, Raphael Manhães Pessanha, Renan Pazini Borges, Wesley Rocha Grippa, Anna Clara Silva Victor de Souza, Leticia Batista de Azevedo, Marcelo Brener Nascimento Carlini, Lizandra Zanetti Miranda, Etreo Junior Carneiro da Silva Minarini, Karolini Zuqui Nunes, Luís Carlos Lopes-Júnior. Cardiac Biomarkers and Electrocardiographic Changes in Women with Breast Cancer Undergoing Chemotherapy: A Prospective Study. Brazilian Journal of Oncology 2026; 22. DOI: 10.1055/s-0046-1825244