Fragmented QRS as an Early Marker of Radiation-Induced Cardiotoxicity in Lung Cancer Patients: A Controlled Observational Study

Background Fragmented QRS (fQRS) is an electrocardiographic marker reflecting myocardial scarring and conduction heterogeneity and has been linked to adverse cardiac outcomes. Cardiac exposure during thoracic radiotherapy (RT) may contribute to subclinical myocardial injury. Objectives To assess the incidence and determinants of fragmented QRS development in lung cancer patients undergoing curative-intent radiotherapy. To our knowledge, this study represents the first controlled evaluation of fragmented QRS as an early electrocardiographic marker of radiation-induced cardiotoxicity in lung cancer patients. Methods Between September 2020 and September 2023, 34 lung cancer patients treated with curative-intent radiotherapy were compared with 40 sociodemographically matched controls. Patients were aged ≥ 18 years and had local advanced lung cancer. Individuals with cardiac implantable electronic devices, acute coronary syndrome, systemic connective tissue disease, sarcoidosis, or inadequate electrocardiographic data were excluded. All participants underwent post-treatment assessment using a standard 12-lead electrocardiogram. Controls underwent a single 12-lead ECG at enrollment. Fragmented QRS was identified according to established criteria. Results Fragmented QRS was observed in 9 of 34 patients (26.5%) in the radiotherapy group and in 3 of 40 controls (7.5%). The prevalence of fQRS was significantly higher among patients who received radiotherapy (p = 0.027). Conclusions Fragmented QRS appears to occur with increased frequency in lung cancer patients treated with curative-intent radiotherapy and may represent an early electrocardiographic marker of radiation-induced cardiotoxicity. Careful attention to cardiac dose during treatment planning, routine ECG surveillance, and additional cardiac evaluation should be considered in patients with detected fQRS.