Impact of adjuvant hormone therapy on cardiac function and lipid profiles in breast cancer patients: a prospective cohort study

Background/Introduction Advances in oncological treatment have improved survival in breast cancer patients, yet treatment-related cardiovascular (CV) toxicity remains a significant concern. Hormone therapy (HT) is a cornerstone of treatment for hormone receptor-positive breast cancer, but its direct effects on cardiac structure, function, and metabolic parameters are not fully understood. Purpose This study aimed to evaluate the impact of HT on longitudinal changes in cardiac function, assessed by echocardiography, and metabolic parameters in breast cancer patients who had complete cardiotoxic chemotherapy. Methods A single-centre, prospective cohort study was conducted at a tertiary referral cancer centre between March 2015 and April 2022. We enrolled 579 breast cancer patients who completed chemotherapy (anthracycline or HER2-targeted agents) and underwent serial echocardiography and lipid profile testing. Patients were divided into two groups; those receiving adjuvant HT (n=297) and those who did not (n=282). The primary outcome was the change in left ventricular ejection fraction (LVEF), global longitudinal strain (GLS), and serum lipid levels from baseline in final follow-up (median 372 days). Results Baseline characteristics and cumulative anthracycline doses were comparable between groups. At the final follow-up, the HT group demonstrated a significantly greater decline in LVEF (59.9±7.2% vs. 62.0±6.4%, P <0.001) and more impaired GLS (-16.8±3.3% vs. -18.5±3.1%, P <0.001) compared to the non-HT group. Cancer therapeutics-related cardiac dysfunction (CTRCD) occurred more frequently in the HT group (12.5% vs. 7.1%, P=0.030). Furthermore, HT was associated with significant increase in total cholesterol and low-density lipoprotein (LDL) cholesterol (estimated mean difference 6.16 mg/dL, P <0.001). Longitudinal changes in LDL-cholesterol were inversely correlated with LVEF changes (partial γ=-0.151, P <0.001) and positively correlated with GLS changes (partial γ=0.209, P <0.001). No significant difference was observed in the 2-year incidence of heart failure hospitalization or urgent visits between the groups (4.7% vs. 3.2%, P=0.335). Conclusions Adjuvant HT in breast cancer patients is associated with significant elevations in LDL-cholesterol and a subclinical deterioration in cardiac systolic function. These findings suggest that HT-induced dyslipidaemia may contribute to subclinical cardiac dysfunction, highlighting the need for proactive CV monitoring and metabolic management in this population.