Cancer-associated thrombosis — Rapid

Synopsis

Recognise venous thromboembolism in a high-risk cancer population, confirm it with the correct first-line imaging and individualise anticoagulation around bleeding, thrombocytopenia, interactions, procedures and ongoing tumour activity.

Cancer increases thrombosis through tumour procoagulants, inflammation, platelets, stasis, surgery, systemic therapy and central venous devices; risk persists while cancer is active.
Key presentations are unilateral leg or arm swelling and pain, unexplained breathlessness, pleuritic pain, haemoptysis, syncope or catheter dysfunction; fever does not exclude clot.
First-line DVT imaging is proximal leg-vein ultrasound and first-line PE imaging is CTPA when suitable; D-dimer is often raised by cancer and is useful only within a validated low-probability algorithm.
Do not delay therapeutic anticoagulation in a likely VTE when imaging is delayed and bleeding risk is acceptable; obtain diagnostic confirmation as soon as possible.
NICE recommends considering a direct-acting oral anticoagulant for confirmed proximal DVT or PE in active cancer, but tumour site, interactions, absorption, renal function and procedures determine whether LMWH is safer.
Luminal gastrointestinal or genitourinary cancer, severe thrombocytopenia, intracranial disease and active bleeding require individual specialist selection and sometimes dose interruption or modification.
Treat for at least 3 to 6 months and review continuation while cancer or anticancer treatment remains active; a calendar stop date must not replace recurrence and bleeding reassessment.
Do not use an inferior vena cava filter routinely; reserve it for selected acute VTE when anticoagulation is genuinely contraindicated or has failed after review, with a retrieval plan.

Key red flags

Hypotension, rising lactate, syncope, severe hypoxaemia or right-ventricular strain suggests high-risk pulmonary embolism.

A tense cyanotic painful leg, sensory loss or weak arterial signals suggests phlegmasia and threatened limb viability.

New headache, neurological deficit or reduced consciousness before anticoagulation raises intracranial metastasis, haemorrhage or stroke and changes immediate risk.

Haematemesis, melaena, haematuria, falling haemoglobin or severe thrombocytopenia requires an explicit bleeding-versus-thrombosis decision rather than automatic cessation or continuation.

Catheter dysfunction, unilateral arm or neck swelling and collateral veins raises upper-extremity thrombosis or central venous obstruction.

Pulmonary embolism

Unexplained dyspnoea, pleuritic pain, tachycardia, hypoxaemia, haemoptysis or syncope can occur with a normal chest examination.

High-risk PE

Hypotension, shock, altered consciousness, severe hypoxaemia or right-heart failure indicates threatened circulation and possible reperfusion need.

Investigation priorities

First-line proximal leg-vein ultrasoundFirst stepFirst line

Confirm or exclude clinically suspected proximal lower-limb DVT without contrast or radiation.

First-line CT pulmonary angiographyFirst line

Demonstrate pulmonary arterial thrombus and assess right heart and alternative thoracic causes.

Management branches

Suspected VTEImage promptly and anticoagulate safely

A cancer patient develops a compatible limb, chest or catheter symptom.

Assess haemodynamic and bleeding risk, use the validated DVT or PE probability pathway and obtain ultrasound or CTPA without attributing symptoms automatically to malignancy.
Start interim therapeutic anticoagulation if clinical probability is significant and imaging is delayed, after platelet, renal, bleeding and procedure assessment.
Confirm diagnosis and anatomical extent, then document the agent, dose, monitoring, interaction and early review plan.

Key medicines

ApixabanGive 10 mg orally twice daily for 7 days, then 5 mg twice daily for treatment of acute DVT or PE; any reduction after 6 months is a deliberate recurrence-versus-bleeding decision under the cancer thrombosis plan.Avoid active clinically significant bleeding and review renal and liver function, strong CYP3A4 or P-glycoprotein interactions, luminal tumour, thrombocytopenia, vomiting, procedures and neuraxial timing.

Low-molecular-weight heparinUse the product-specific weight-based treatment regimen; for dalteparin in cancer-associated VTE a licensed course uses 200 IU/kg subcutaneously once daily for the first 30 days, then approximately 150 IU/kg once daily for months 2 to 6, subject to product maximums and platelet or renal adjustment.Check actual weight, creatinine clearance and platelets, monitor bleeding and heparin-induced thrombocytopenia and plan procedures and neuraxial anaesthesia carefully; accumulation can occur in renal failure.

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