Longitudinal Changes in QTc Interval in Cancer Patients After the Initiation of Systemic Therapy: Analysis of the ONCOECHO Study Cohort

Background/Objectives: Anticancer therapies are associated with a prolongation of QT interval of electrocardiogram (ECG), increasing the risk of arrhythmias. To evaluate this risk in cardiovascular disease-free subjects with cancer, ECG recorded at baseline, months 3, 6 and 12 from 291 participants from the ONCOECHO database were analyzed. Methods: Both Fridericia (QTcF), considered as standard, and Bazett (QTcB) formulas were used to calculate corrected QT (QTc). Results: The study cohort consisted of 61.8% subjects with breast cancer, 26.5% with hematologic malignancies, 7.3% with colorectal cancer and 4.4% of patients with kidney cancer. At baseline, six patients had a QTcF ≥ 460 ms and one ≥ 500 ms. QTcF values differed significantly across time points (p = 0.0125), with a significant increase between baseline and month 6 (400.9 ± 29 ms vs. 409.6 ± 25 ms, p = 0.0075). Use of the Bazett formula resulted in 5.49 (95% CI 3.28–9.19) higher odds of identification of QTc ≥ 460 ms than with the Fridericia rule. A LASSO logistic regression model identified age, QTcF at baseline and month 3 to increase odds of QTcF ≥ 460 ms, whereas higher ejection fraction was associated with decreased odds. Conclusions: Analysis shows that cancer patients receiving cardiotoxic therapy are at relatively low risk of QTc prolongation, but choosing the appropriate QTc correction formula is essential.