Association between QT prolongation and cardiovascular mortality in cancer patients

Cancer patients' vulnerability to QT prolongation contradicts certain anti-cancer drug usage. Until now, the QT prolongation's impact on CV mortality in cancer patients remains unclear, potentially biasing therapeutic decisions.

This retrospective observational cohort included adult cancer patients with an electrocardiogram (ECG) performed in a tertiary hospital in Taiwan. The first performed ECGs after cancer diagnosis (n = 59,568) were analyzed. The corrected QT intervals by Bazett (QTcB), Fridericia (QTcFri), and Framingham (QTcFra) formulae were used to predict the 90-day and one-year CV mortality according to the Taiwan death registry.

The AUC of QTcB (90 days: 0.70, 1 year: 0.68) for predicting CV mortality was better than QTcFri and QTcFra (90 days: 0.63 and 0.50, 1 year: 0.65 and 0.56). Using the restricted cubic spline regression model adjusted by age and comorbidities, QTcB increased a significant but trivial risk of CV mortality at 90 days (hazard ratio, 1.007, P = 0.02) and one year (1.006, P < 0.01). Compared to those with QTcB < 500ms, the patients with QTcB ≥ 500ms were older and had more comorbidities and mortalities within one year. The incidence of sudden death and ventricular arrhythmias was only 0.2%. After adjusting for comorbidities, QTcB was neither associated with 90-day nor one-year CV mortality. In the patients already with QTcB ≥ 500ms, the patients receiving the unexpected uses of QT-prolonging drugs were not associated with higher one-year CV mortality than those without (P = 0.14).

Rather than a prolonged QT interval per se, comorbidities contributed to CV mortality and irreversible outcomes in cancer patients.