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Breast Cancer — SCE Medical Oncology MCQ

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HardBreast CancerBreast CancerSCE Medical Oncology

A woman with metastatic HR-positive, HER2-negative breast cancer takes ribociclib 600 mg daily on days 1–21 of each 28-day cycle. QTcF is 495 ms, potassium and magnesium are normal and she has no arrhythmia symptoms. What does the current UK SmPC require?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Interrupt until QTcF is below 481 ms, then resume at 400 mg daily

Explanation lettering: B = shown as A · E = shown as B · A = shown as E

A is correct. In advanced or metastatic breast cancer, QTcF above 480 and up to 500 ms requires interruption until it resolves below 481 ms, then resumption at the next lower dose; from 600 mg that is 400 mg. Electrolytes and interacting QT-prolonging or CYP3A4-inhibiting medicines should also be reviewed. Permanent discontinuation is reserved for specified recurrent or serious abnormalities, not this first asymptomatic value. Switching agents does not remove the need to manage the present toxicity, beta blockade is not the SmPC algorithm, and unchanged dosing risks further prolongation. The original answer was correct; this version makes the exact dose explicit.

Reference: Kisqali UK Summary of Product Characteristics: https://www.medicines.org.uk/emc/product/8110/smpc