The use of warfarin for venous thromboembolism (VTE): Practical problems for patients and resource implications for an oncology unit

Abstract

6088 Background: Recent evidence has suggested improved efficacy with low molecular weight heparin (LMWH) over oral coumarins for the treatment of cancer patients with VTE. Oral anticoagulants present multiple practical problems for patients undergoing chemotherapy, including side-effects, disruption of anticoagulation for invasive procedures, multiple drug interactions and multiplicity of patient visits. To assess the practice implications of these issues, a review was carried out in a busy medical oncology unit. Methods: A retrospective review of all patients treated with the coumarin derivative, warfarin for VTE during the last year was undertaken. Patients on prophylactic warfarin for central venous devices were excluded. Computerised laboratory records were used to identify patients. Patients were assessed for adverse events and therapeutic efficacy. The extra volume of work involved in monitoring blood tests and treating complications was quantified. Results: 55 patients with VTE were treated with warfarin from 07/01/04 to 06/30/05. The majority (73%) had metastatic carcinoma. 21 invasive interventions required disruption of anticoagulation. 90% of these were in patients with metastatic disease. Each patient was subtherapeutic (International normalised ratio <2.0) for a mean of 30.7 days (25% of mean duration of anticoagulation). There were 8 admissions for haemorrhage. Nine patients died on warfarin, 8 of whom had metastatic disease. In one patient with significant cardiac comorbidity warfarin therapy contributed to early death. No patterns of drug interactions were identified. A total of 1,369 coagulation tests were performed. There were 382 extra blood test visits, representing 26% of all day ward blood visits. On treatment, 13 patients (24%) were changed from warfarin therapy to LMWH. In 4 patients there was progression of VTE. In 9 patients, all with metastatic disease LMWH was substituted to qualitatively improve patient care by minimising hospital visits and facilitating home based care. Conclusions: This study identifies the high rate of treatment change to LMWH and quantifies the extra resource utilization with coumarin therapy. This supports the increased primary use of LMWH in selected cancer patients. No significant financial relationships to disclose.