Background: Low molecular weight heparin (LMWH) is the standard treatment for long-term management and second-ary prophylaxis of acute venous thromboembolism (VTE) in patients with cancer. However, evidence-based guidance for anticoagulation (AC) management in oncology patients receiving chemotherapy remains unavailable. We assessed reports of adverse drug events (ADEs) in VA Loma Linda (VALL) oncology patients who received warfarin vs enoxaparin during their cancer treatment in the oncology clinic.
Methods: A retrospective chart review was performed on all oncology patients who received warfarin or LMWH during chemotherapy treatment at the VALL medical oncology clinic from January 1, 2009, to April 10, 2015.
Results: We screened 400 patients receiving chemotherapy while also on AC treatment; 18 subjects met inclusion criteria. At baseline: mean (+SD) age was 64.66 (+9) years; 78% were male; a mean dose of 38.72 (+16.5) mg/week of warfarin had been used during chemotherapy. Nine subjects were on warfarin, and 9 subjects were on LMWH. More ADEs occurred (supra-therapeutic international normalized ratio [INR] and bleeding) with patients on warfarin. Approximately 67% of patients on warfarin experienced an ADE com-pared with 22% of the patients on enoxaparin. No incidences of VTE were found in patients on warfarin; 1 patient experienced a deep vein thrombosis while on enoxaparin. Patients receiving chemotherapy and warfarin had their INR monitored at a mean of 3.78 (+3.67) times over 2.69 (+1.75) months compared with those on enoxaparin, which doesn’t require any monitoring.
Conclusions: We found there is a marginal association between oncology patients on warfarin and ADEs; more ADEs were associated with oncology patients on warfarin than with those on enoxaparin. This is evident by the chi-square test: X2 (1) = 3.6, n = 18, P = .058 (P > .05). Therefore, the association can be interpreted that oncology patients on warfarin have an increased risk of unstable INR results and bleeding.
