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People with cancer get blood clots more often than others. A score built from the cancer type and routine blood tests picks out those at higher risk, and in two placebo-controlled trials a low-dose blood-thinning tablet reduced clots but caused more bleeding. United States guidance says it may be offered; surveys in the Netherlands and China found most specialists do not use the score.
The score. The Khorana score was derived in 2,701 outpatients starting chemotherapy and validated in 1,365 more. It gives points for the site of the cancer (two for very high-risk sites, one for high-risk sites) and one point each for a platelet count of 350 x 10^9/L or more, haemoglobin below 100 g/L or use of an erythropoiesis-stimulating agent, a white cell count above 11 x 10^9/L, and a body mass index of 35 or more. Symptomatic clots over a median 2.5 months occurred in 0.8 and 0.3 per cent of the low-risk group and 7.1 and 6.7 per cent of the high-risk group in the two cohorts.
The trials. AVERT randomised 574 patients with a score of 2 or more starting chemotherapy to apixaban 2.5 mg twice daily or placebo: clots occurred in 4.2 per cent against 10.2 per cent (hazard ratio 0.41), and major bleeding in 3.5 per cent against 1.8 per cent (hazard ratio 2.00). CASSINI randomised 841 patients to rivaroxaban 10 mg daily or placebo: the primary endpoint at 180 days was 6.0 against 8.8 per cent (hazard ratio 0.66, P = 0.10), which was not statistically significant; during the period patients were actually taking the drug it was 2.6 against 6.4 per cent (hazard ratio 0.40), with major bleeding 2.0 against 1.0 per cent.
The guidance. The 2019 ASCO update, published in 2020, states that clinicians "may offer thromboprophylaxis with apixaban, rivaroxaban, or LMWH to selected high-risk outpatients with cancer", that thromboprophylaxis is not routinely recommended for all outpatients, and that patients should be periodically assessed for risk; the 2023 update revised the surgical and treatment recommendations.
The measured gap. In a 2025 Dutch survey of 38 medical oncologists treating pancreatic cancer, 63 per cent had never prescribed thromboprophylaxis to ambulatory patients on chemotherapy, 11 per cent used the Khorana score and 3 per cent always discussed clot risk with patients; the commonest reason given was the lack of a national guideline recommendation. In a 2025 survey of 235 physicians in Chinese tertiary hospitals treating advanced lung cancer, 57.8 per cent routinely used the score and 49.4 per cent said they were familiar with it.
Shares Venous Thromboembolism Prophylaxis and Treatment in Patients With Cancer: ASCO Guideline Update, Venous thromboembolism (VTE), Cancer-associated thrombosis prevention and treatment, Knowledge reaches practice too slowly and the tags protocol-upgrade, upgrade:proven-unevenly-used.
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Shares Toxicity and quality of life are undervalued and the tags protocol-upgrade, upgrade:proven-unevenly-used, precision.
Shares Knowledge reaches practice too slowly, Toxicity and quality of life are undervalued and the tags protocol-upgrade, upgrade:proven-unevenly-used.
Shares Knowledge reaches practice too slowly, Toxicity and quality of life are undervalued and the tags protocol-upgrade, upgrade:proven-unevenly-used, precision.
Shares Knowledge reaches practice too slowly, Non-small-cell lung cancer and the tags protocol-upgrade, upgrade:proven-unevenly-used.
Shares Knowledge reaches practice too slowly, Toxicity and quality of life are undervalued and the tags protocol-upgrade, upgrade:proven-unevenly-used.
Shares Knowledge reaches practice too slowly, Pancreatic ductal adenocarcinoma and the tags protocol-upgrade, upgrade:proven-unevenly-used.
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