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Cancer-associated thrombosis
Cancer greatly raises the risk of venous thrombosis; treat with a direct oral anticoagulant (DOAC) or low molecular weight heparin (LMWH) for a minimum of 6 months, continuing while the cancer remains active, and choose LMWH or apixaban when there is a GI or urinary tract tumour with bleeding risk.
Why it matters in the exam
Thrombosis in cancer patients appears in the exam in internal medicine and oncology: which anticoagulant to choose, for how long, what to do with a pulmonary embolism found incidentally on a follow-up CT, and what to do when thrombosis recurs despite treatment. Questions on primary prevention in ambulatory patients by the Khorana score also appear.
Common distractors are treating an incidental embolism as a finding that needs no treatment, choosing warfarin as preferred treatment, or choosing a DOAC for an unresected bowel or bladder tumour that bleeds. Also remember interactions between DOACs and oncology drugs, and the adjustment needed when platelets fall below 50,000.
Key points
- Thrombosis in a cancer patient is treated with a DOAC or LMWH for a minimum of 6 months, continued while the cancer is active or treated.
- With an unresected bowel or urinary tract tumour choose LMWH or apixaban, because of more bleeding with other DOACs.
- A pulmonary embolism found incidentally on a follow-up CT is treated like a symptomatic embolism.
- Recurrent thrombosis on treatment is managed by switching to LMWH or increasing the dose, after checking adherence and mechanical causes.
- A Khorana score of 2 or more identifies ambulatory patients who may benefit from primary prevention.
Summary table
| Situation | Recommendation | Exam detail |
|---|---|---|
| Treatment of a new thrombosis | DOAC (apixaban, edoxaban, rivaroxaban) or LMWH | A minimum of 6 months, continued while the cancer is active or being treated |
| Unresected bowel or urinary tract tumour | LMWH or apixaban | Edoxaban and rivaroxaban showed more GI bleeding |
| Incidental pulmonary embolism | Treat like a symptomatic embolism | Including a single segmental embolism, with an individual decision in subsegmental |
| Recurrent thrombosis on treatment | Check adherence, then switch to LMWH or increase the LMWH dose | Exclude a mechanical cause — tumour pressing on the vessel |
| Catheter-related thrombosis | Anticoagulation for at least 3 months | If the catheter works and is needed — it may stay |
| Primary prevention in an ambulatory patient | Khorana score of 2 or more — consider apixaban, rivaroxaban or LMWH | Points: stomach or pancreas — 2; lung, lymphoma, gynaecological, bladder, testis — 1; platelets, haemoglobin, leucocytes and BMI — 1 each |
| Special situations | Platelets below 50,000 — reduce the dose or pause; major abdominal cancer surgery — extended prophylaxis for 4 weeks | Lenalidomide or thalidomide in myeloma — aspirin or LMWH |
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Sources
- ASCO Guideline: Venous thromboembolism prophylaxis and treatment in patients with cancer, 2023 — Recommendations
- ITAC International Clinical Practice Guidelines for the treatment and prophylaxis of venous thromboembolism in patients with cancer, 2022 — Treatment and prophylaxis
- ESC Guidelines on cardio-oncology, 2022 — Venous thromboembolism
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.