OncologyTier 1Disease (DEADMAN)

Thromboembolism

Description

Cancer-associated thrombosis (CAT) - VTE (DVT/PE) arising in the setting of active malignancy - a leading cause of morbidity/mortality in cancer patients, second only to the cancer itself
Includes catheter-related thrombosis (central venous access devices), visceral vein thrombosis (portal, splenic, mesenteric - often incidental on staging CT), and classical DVT/PE
Incidental (asymptomatic) PE/DVT found on staging CT is common and treated the same as symptomatic VTE - not a bystander finding

Cancer patients have a ~4-7x increased VTE risk vs the general population; risk further multiplied by active chemotherapy
Highest-risk tumours: pancreatic, gastric, brain, ovarian, lung, haematological malignancy
VTE is a leading cause of death in ambulatory cancer patients receiving chemotherapy

Virchow's triad, cancer-amplified: tumour cells directly activate coagulation (tissue factor expression), venous stasis (immobility, mass compression), endothelial injury (catheters, surgery, chemotherapy)
Chemotherapy - independently procoagulant (endothelial damage, reduced natural anticoagulants); antiangiogenic agents (bevacizumab) and some hormonal therapies (tamoxifen) carry particular VTE risk
Central venous catheters - major cause of upper-limb DVT in cancer patients
Paraneoplastic hypercoagulability - can precede cancer diagnosis (unprovoked VTE is itself a trigger for occult malignancy screening in appropriate-age patients)

Clinical

Standard DVT/PE presentation, but maintain a lower threshold for imaging in cancer patients given elevated baseline risk and atypical/subtle presentations
D-dimer is unreliable in active cancer (frequently elevated from malignancy itself) - imaging (compression ultrasound, CTPA/V-Q) is the diagnostic step, not a D-dimer-gated pathway as used in low-risk populations

Risk stratification for primary prophylaxis

Khorana score - predicts chemotherapy-associated VTE risk in ambulatory patients (tumour site, pre-chemo platelet/leucocyte count, haemoglobin/ESA use, BMI) - guides consideration of primary thromboprophylaxis in high-risk outpatients starting chemotherapy

A. Treatment of confirmed CAT

LMWH or a DOAC (apixaban, rivaroxaban, edoxaban) for at least 6 months are both first-line - DOACs preferred for convenience where bleeding risk is not elevated
Caution/avoid DOACs in GI and genitourinary malignancy (particularly luminal GI cancer) - increased major bleeding risk observed in trials; LMWH preferred in this setting
Extend anticoagulation beyond 6 months while active cancer/treatment continues - VTE recurrence risk remains high as long as the malignancy is active
Vitamin K antagonists - inferior efficacy compared with LMWH/DOACs in cancer, generally avoided

B. Primary thromboprophylaxis

Hospitalised cancer patients (medical admission, post-surgical) - pharmacological prophylaxis as for other high-risk inpatients unless contraindicated
Ambulatory chemotherapy patients - primary prophylaxis not routine for all, but considered in high Khorana score patients, and specifically for pancreatic cancer patients on active chemotherapy with low bleeding risk (strongest evidence base for this group)

C. Incidental VTE

Treat incidental/asymptomatic PE or proximal DVT found on staging imaging the same as symptomatic VTE - equivalent mortality risk if untreated

D. Catheter-related thrombosis

Anticoagulation as for other VTE; catheter usually does not need removal if still functioning and required, unless infection or ongoing symptoms despite anticoagulation

Pancreatic, gastric, brain, ovarian, lung, and haematological malignancy - highest risk tumour types
Active chemotherapy, antiangiogenic therapy (bevacizumab), central venous catheters, immobility, recent surgery
Unprovoked VTE in an older patient - prompts consideration of occult malignancy work-up

CAT carries a higher recurrence rate and higher bleeding risk on anticoagulation than non-cancer VTE
Independently associated with worse overall survival - VTE diagnosis often prompts reassessment of goals of care/prognosis discussion, not purely an isolated vascular event
Anticoagulation duration is tied to disease activity - continue while cancer is active/being treated, reassess once in remission or off active therapy
Recurrent VTE despite adequate anticoagulation - consider dose escalation (LMWH), switching agents, or IVC filter in select circumstances (rarely first-line)

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