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Low-dose prophylactic apixaban (Eliquis) reduced risk of venous thromboembolism (VTE) for patients starting cancer chemotherapy, the AVERT trial showed.

Proximal deep-vein thrombosis or pulmonary embolism occurred at a rate of 4.2% with 2.5 mg apixaban twice daily vs 10.2% with placebo (HR 0.41, P<0.001) during 180 days of follow-up in the intermediate-to-high-risk ambulatory population studied.

The number needed to treat of 17 to prevent one VTE was "driven predominantly by a lower rate of pulmonary embolism in the apixaban group," Philip Wells, MD, of the Ottawa Hospital in Ontario, and colleagues reported in the New England Journal of Medicine.

As expected, the non-vitamin K antagonist oral anticoagulant (NOAC) increased the risk of major bleeding. The rate by International Society on Thrombosis and Hemostasis criteria was 3.5% vs 1.8% (10 vs 5 cases, HR 2.00, P=0.046) among the 563 who got at least one dose of apixaban or placebo by the end of follow-up. (For an easy-to-digest infographic on the study results, click here.)

But, the researchers pointed out the similar rate during the treatment period (2.1% vs 1.1%, HR 1.89, 95% CI 0.39-9.24) with a number needed to harm of 100. No fatal bleeding or bleeding into critical organs was seen. Notably, "major bleeding occurred mainly in patients who had entered the trial with gastrointestinal or gynecologic cancer."

Wells' group noted that prevention is important for cancer patients, as treatment with therapeutic anticoagulation can be clinically challenging, "because it often involves daily injections of low-molecular-weight heparin and is associated with a high risk of thrombosis recurrence and serious bleeding complications."

Parenteral agents for thromboprophylaxis are effective but "not routinely recommended in practice guidelines" due to a modest absolute risk reduction, increased risk of major bleeding, high cost, and the inconvenience of daily injections, they pointed out.

The trial design attempted to select patients who would stand to benefit more from prophylaxis by including only those with a Khorana score for VTE risk of 2 or greater on the 6-point scale.

AVERT included 574 patients with newly diagnosed cancer or progression of known cancer after complete or partial remission and who were starting a new course of chemotherapy expected to last at least 3 months.

Conditions raising risk for clinically significant bleeding were cause for exclusion, as was hepatic disease associated with coagulopathy, skin cancer, acute leukemia, or myeloproliferative neoplasm, short life expectancy, renal insufficiency, or low platelet count.

While the researchers suggested that the findings should be broadly applicable across types of cancer, they noted that the low proportion of patients with renal dysfunction (5.9%) may limit generalizability to that group, which is known to have a higher bleeding risk.