Four weeks of blood-clot prevention after major abdominal or pelvic cancer surgery

The evidence. A meta-analysis of seven randomised and prospective studies with 4,807 patients found that extending prophylaxis to two to six weeks after abdominal or pelvic cancer surgery reduced all venous thromboembolism from 5.6 to 2.6 per cent (relative risk 0.44, number needed to treat 39) and proximal deep vein thrombosis from 2.8 to 1.4 per cent, without a significant increase in major bleeding (1.8 against 1.0 per cent). Symptomatic pulmonary embolism and three-month mortality did not differ significantly, which is the honest limit: much of the reduction is in clots found by scanning. A larger 2021 meta-analysis of 68 studies with more than 1.6 million patients found clinical clots fell from 2.1 to 1.0 per cent with extended low-molecular-weight heparin, again without more clinically relevant bleeding.

The guidelines. Extended prophylaxis after cancer surgery is recommended by major professional societies, as the Medicare study below notes, and the 2023 ASCO guideline update added the tablets apixaban and rivaroxaban as options for it, with a weak recommendation. That matters for adherence, because tablets can replace four weeks of injections.

The measured gap. In SEER-Medicare data for 23,527 patients over 64 having colorectal cancer resection in 2016 and 2017, 4.7 per cent received extended prophylaxis within seven days of discharge; 10.2 per cent at NCI-designated centres and 1.7 per cent at non-teaching hospitals. The authors conclude that use "remains limited even in large, specialized hospitals". No source OnCo found measures this in the NHS.