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Ribociclib QTc — SCE Medical Oncology MCQ

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HardBreast CancerRibociclib QTcSCE Medical Oncology

A 65-year-old woman on ribociclib + letrozole has routine ECG monitoring showing QTc 475 ms (baseline 410 ms). She is asymptomatic. At what QTc threshold should ribociclib be interrupted?

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Correct answer: D — Interrupt if QTcF rises above 480 ms and correct reversible contributors

Ribociclib is interrupted when QTcF exceeds 480 ms, with electrolytes and interacting medicines corrected before any permitted resumption. Interrupt if QTcF rises above 450 ms and correct reversible contributors: 450 ms is not the product-information interruption threshold. Interrupt if QTcF rises above 500 ms and correct reversible contributors: waiting for 500 ms misses the earlier interruption threshold. Interrupt if QTcF rises sixty milliseconds from baseline and remains below 480 ms: change from baseline informs risk, but the specified routine threshold is above 480 ms. Interrupt if QTcF rises above 480 ms and permanently discontinue after recovery: first 481–500 ms prolongation can permit recovery and dose-modified resumption.

Reference: Kisqali 200 mg UK summary of product characteristics (Current UK SmPC, updated July 2026): https://www.medicines.org.uk/emc/product/8110/smpc