Prescribing of Low-Molecular-Weight Heparin and Warfarin in Patients with Acute Venous Thromboembolism and Active Cancer

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Background: Malignancy is a significant risk factor for venous thromboembolism (VTE), conferring a 4- to 7-fold increased risk in patients with cancer. Because of its effect on certain tumors, low-molecular-weight heparin (LMWH) has been evaluated as a treatment option for cancer and as an alternative to traditional warfarin therapy in patients with active cancer. LMWH is associated with a reduced recurrence of VTE, fewer adverse bleeding events, and, in some instances, decreased mortality. The American College of Chest Physicians/American Society of Clinical Oncology has recommended LMWH for at least the initial 3 to 6 months when treating VTE in patients with cancer, based on the positive outcomes associated with LMWH.

Objective: The purpose of this study was to evaluate physician prescribing patterns for LMWH or warfarin in patients with acute VTE and active cancer.

Methods: We conducted a retrospective chart review of hospitalized patients at a community teaching hospital with an affiliated regional cancer center located in a rural area of the United States. Patients included in the analysis had an International Classification of Diseases, Ninth Revision code indicative of any cancer type and a concomitant code for any VTE. The primary outcome was the drug prescribed at discharge for the treatment of VTE. Secondary outcomes included specialty of the prescribing physician, adverse bleeding events, and the need for transfusion. VTE treatment regimen was evaluated using the binomial test, and logistic regression analysis was used to determine correlation of the prescriber’s specialty with the patient’s prescribed regimen.

Results: Of 129 patients included in the analysis, 107 (82.9%) were prescribed warfarin compared with 9 (7%) who were prescribed LMWH. Hematologists and oncologists were more likely to prescribe LMWH than general practitioners (odds ratio, 7.8; 95% hazard ratio, 1.5-42). Seven patients had a documented adverse bleeding event and 2 patients required a transfusion. Four of the 7 adverse bleeding events and 1 of the 2 transfusions occurred in the group receiving vitamin K antagonist therapy.

Conclusion: Physicians in our system were significantly more likely to prescribe warfarin for acute treatment of VTE in patients with active cancer—despite consistent evidence and multiple evidence­-based guidelines recommending treatment with LMWH in this patient population. This was lower than other observations in Canadian populations but may more accurately represent nonteaching centers in the United States, particularly those in rural areas. Specialists in oncology were significantly more likely to prescribe LMWH than generalists.