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DOAC Considerations with Tamoxifen — SCE Palliative Medicine MCQ

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HardRespiratory SymptomsDOAC Considerations with TamoxifenSCE Palliative Medicine

A 60‑year‑old woman with advanced breast cancer on tamoxifen develops a pulmonary embolism and is started on low‑molecular‑weight heparin. After 2 weeks, she asks about switching to a direct oral anticoagulant for convenience. What consideration is specific to her situation?

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

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Correct answer: E — Tamoxifen increases VTE risk and may interact with DOACs via CYP450 and P‑glycoprotein pathways; choice of DOAC requires specific review of drug interactions

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

The correct answer is C. UK NICE guidance (NG158) mandates that, in patients with active cancer and VTE, choice of anticoagulant must consider interactions with cancer therapies, including tamoxifen, which increases VTE risk and may affect DOAC metabolism via CYP3A4 and P‑gp. DOAC blood levels are altered by inhibitors of these pathways; hence, DOAC selection requires drug‑specific review. Distractor A is false—tamoxifen increases, not decreases, VTE risk. B is incorrect—interactions are drug‑specific, not universal across chemotherapies. D is false—DOACs may be used in selected cancer patients per NICE. E is incorrect—the duration of LMWH is individualized (3–6 months) not lifelong.

Reference: NICE NG158 (2020) recommendations on anticoagulation in active cancer; GOV.UK drug‑safety update on DOAC interactions (P‑gp/CYP3A4 inhibitors)