Evaluation of electrocardiographic repolarization parameters in patients who received ribociclib and palbociclib therapy

Introduction: Ribociclib and palbociclib are the inhibitors of cyclin-dependent kinase (CDK) 4/6 activity which have been used in the treatment of metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative breast cancer. QT interval prolongation has been the main reported adverse effect in Phase III trials of ribociclib and palbociclib therapy. In the present study, we aimed to evaluate electrocardiographic (ECG) changes in patients who received palbociclib and ribociclib therapy. Materials and Methods: Sixty women with metastatic HR-positive, human epidermal growth factor-2-negative breast cancer were included in the study. Baseline ECG and echocardiographic examinations of these patients were done. Second control electrocardiogram was obtained on the 14th day of first-cycle therapy. PR interval, corrected QT (QTc) interval, QT dispersion (QTD), and QRS duration were calculated. Results: Heart rate, PR interval, QRS, QT, QTc, QTD, and corrected QTD duration did not differ before and after CDK 4/6 treatment. Two patients who received ribociclib and palbociclib treatment had basal QTc duration higher than 450 ms (458 ms and 465 ms, respectively). The 14th-day QTc intervals of these patients were found to be 318 ms and 406 ms, respectively. After CDK 4/6 treatment, only two patients had QTc interval of 469 ms and 507 ms. The mean change of QTc interval before and during the 14th day of CDK 4/6 therapy was 7.38 ± 35.049 ms. When palbociclib and ribociclib treatments were analyzed separately, the baseline and 14th day of QTc interval were 415 ± 31.5 versus 428.11 ± 24.52 and 416.13 ± 26.05 versus 420.07 ± 31.32 ms, respectively. Conclusions: Ribociclib and palbociclib treatment was associated with a small statistically insignificant increase in QTc interval. Physicians should be aware of the side effect of these treatments.