Two smaller trials compared LMWHs with warfarin in the treatment of VTE in the setting of cancer. In one trial, seven of 67 enoxaparin-treated patients developed bleeding or recurrent VTE, compared with 15 of 71 warfarin-treated subjects; however, this reduction was not statistically significant (P=0.09).11 In another trial, seven of 100 tinzaparin-treated patients developed recurrent VTE, compared with 16 of 100 warfarin-treated patients (P=0.044).12
Thus, LMWH is the preferred therapeutic agent for both DVT and PE in the setting of malignancy.5 Even so, although the clinical evidence supports LMWH use in the treatment of cancer-associated VTE, it’s worth noting that many of the authors of the cited papers received compensation from large pharmaceutical companies. In addition, the CLOT trial was funded by Pharmacia, which supplied the study drug.
Initial treatment (5-10 days): The American Society of Clinical Oncology (ASCO) guidelines advocate the use of LMWH during the initial five to 10 days following VTE diagnosis. Four other cancer research organization guidelines, National Comprehensive Cancer Network (NCCN), the Italian Association of Medical Oncology (AIOM), the European Society of Medical Oncology (ESMO), and the French National Federation of the League of Centers Against Cancer (FNCLCC), echo this approach, with unfractionated heparin (UFH) or fondaparinux as additional initial treatment depending on the clinical situation—i.e., renal failure, heparin-induced thrombocytopenia (HIT), or bleeding risk.6
Table 2 (below) summarizes recommendations for VTE treatment in cancer patients from all five guideline panels.6
Long-term treatment and duration (3-6 months): All of the panels agree LMWH is the preferred agent for long-term therapy of cancer-related VTE. ASCO supports treatment with LMWH for at least six months; oral VKAs with a targeted INR of 2 to 3 are acceptable when LMWH is not feasible. NCCN, AIOM, ESMO, and FNCLCC recommend an LMWH treatment duration from three to six months (ASCO recommends at least six months).
All of the panels, however, advocate indefinite duration of anticoagulation in patients with such continuing risk factors as active (metastatic, recurrent, or persistent) cancer or chemotherapy treatment.6 AIOM and ESMO specify indefinite LMWH, whereas ASCO does not specify oral VKA or LMWH use. Given the difficulties of managing VKA in the setting of advanced malignancy or chemotherapy, LMWH is the most practical choice, if it’s available and isn’t cost-prohibitive.
LMWH availability: Dalteparin, tinzaparin, and enoxaparin are LMWHs currently available in the U.S. for VTE treatment. Dalteparin is the only FDA-approved LMWH drug for long-term use to treat cancer-associated VTE, although enoxaparin and tinzaparin are used in practice. All three are supplied in prefilled syringes, which make self-administration easier and significantly reduce the risk of dosage error.6
LMWH vs. UFH: LMWH is safer and more efficacious than UFH. A summary of 22 clinical trials (including cancer patients and noncancer patients) by a Cochrane systematic review showed that treatment with LMWH in comparison with UFH results in decreased recurrent VTE, bleeding, mortality, HIT, and osteoporosis.7,13