Key result
CDK4/6 inhibitors linked to new-onset second-degree type 2 AV block in two cases.
Why the study?
Cardiovascular side effects of CDK4/6 inhibitors are uncommon and primarily include QT prolongation, with limited data on other conduction abnormalities such as advanced AV blocks.
Case Report (n=2)
CDK4/6 inhibitors may be associated with severe conduction disorders such as advanced AV block, suggesting a potential need for more frequent ECG monitoring beyond just QT interval surveillance.
Answers are grounded in this paper and cite their sources.
May signal rare conduction toxicity with CDK4/6 inhibitors; hypothesis-generating and should not yet change ECG monitoring practice.
Introduction: A wide spectrum of cardiovascular (CV) toxicity is associated with anticancer treatment, and nearly all chemotherapeutic agents can elicit CV toxicity. Inhibitors of cyclin-dependent kinases 4/6 (CDK4/6Is) have become standard of care in the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer (MBC). CV side effects are uncommon with CDK4/6Is and only include QT prolongation, with a low incidence rate. Case Presentation: This paper describes 2 cases of new-onset second-degree type 2 atrioventricular (AV) blocks requiring permanent cardiac pacing involving 2 women with MBC receiving ribociclib or abemaciclib. Both our patients had no known history or risk factors of cardiac disease and a normal 12-lead resting electrocardiogram (ECG) when diagnosed with breast adenocarcinoma. Both patients have been subjected to surveillance for cardiotoxicity with serial ECG and echocardiography. No left ventricular dysfunction or arrhythmia was found during the follow-up, and cardiac biomarkers were normal. Conclusion: To our knowledge, these are the first cases reported in the literature of new-onset advanced AV blocks in patients under treatment with CDK4/6Is, suggesting the clinical relevance of a more frequent ECG monitoring, besides the QT interval, in these patients.
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Cicini et al. (2021) conducted a case report in Metastatic breast cancer (n=2). CDK4/6 Inhibitors (ribociclib or abemaciclib) was evaluated on New-onset second-degree type 2 atrioventricular block requiring permanent cardiac pacing. Treatment with CDK4/6 inhibitors (ribociclib or abemaciclib) in two women with metastatic breast cancer was associated with the development of new-onset second-degree type 2 atrioventricular block.
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