No Difference Between Treatments for Major Blood Clots in Cancer Patients

Warfarin and a low molecular-weight heparin produced similar results in reducing major blood clots in cancer patients treated for acute venous thromboembolism.

Both the vitamin K antagonist warfarin and tinzaparin, a low molecular-weight heparin (LMWH), reduced major blood clots to a similar extent in cancer patients treated for acute venous thromboembolism (VTE), according to the results of a clinical trial published in JAMA. LMWH did decrease the rate of less serious bleeding events, however.

“The results should provide physicians more confidence to use … LMWH as a first-line therapy for the treatment of VTE in patients with active cancer,” lead author Agnes Y. Y. Lee, MD, of the University of British Columbia in Vancouver, told Cancer Network. “The lower incidence of clinically relevant non-major bleeding with the [LMWH] is also reassuring.”

A total of 49 of 449 (10.9%) patients in the LMWH group had a non-major bleeding event compared with 69 of 451 patients (15.3%) in the warfarin group (P = .004).

The 6-month cumulative incidence of recurrent VTE was 7.2% among patients treated with LMWH compared with 10.5% among patients treated with warfarin (P = .07). The number of major bleeding events was also similar-12 events in LMWH patients compared with 11 in warfarin patients (P = .77). Overall mortality was also similar between the two groups (P = .54).

LMWH is the standard treatment for VTE in cancer patients, recommended over warfarin in guidelines from the National Comprehensive Cancer Network, the American Society of Clinical Oncology, and the American College of Chest Physicians. Because this preference for LMWH is based predominantly on a single large study, the CLOT trial, conducted more than 10 years ago, Lee and colleagues investigated the longer-term use of both LMWH and warfarin.

The current trial, CATCH (Comparison of Acute Treatments in Cancer Hemostasis), is the largest clinical trial to compare the efficacy of LMWH to warfarin for the treatment of acute VTE in patients with cancer. The trial randomized 900 cancer patients with active disease and a history of a VTE-either deep vein thrombosis or pulmonary embolism-to 6 months of daily subcutaneous LMWH injections or warfarin. Patients were followed for 6 months after completion of therapy.

The trial was designed prior to the availability of newer, oral anticoagulants such as apixaban and rivaroxaban. Because warfarin remains the most common type of anticoagulant for patients with cancer, and because these new oral agents are still not recommended for blood clots associated with cancer, the results of the CATCH trial are clinically relevant, the authors noted.

“CATCH reinforces that cancer-associated thrombosis is a diverse disease in terms of patient outcomes and treatment needs. The results, when combined with previous and ongoing studies, are likely to provide us with information that would help us identify those who require LMWH treatment, those who might do well on warfarin, and those who can be treated with a direct oral anticoagulant,” said Lee.