Cancer associated thrombosis in patients taking direct oral anticoagulants (DOACs): Retrospective review of a single institutional series.

Abstract

e14080 Background: Venous thromboembolism (VTE) is a common and often serious complication for patients with malignancy. Even though low molecular weight heparin (LMWH) is recommended as first line therapy for initial and long term anticoagulation, patient choice may demand oral anticoagulants. This retrospective review illustrates the repeated observation of recurrent thromboembolic disease in patients taking the new class of oral anticoagulant, DOAC. Methods: The pharmacy database at our institution was searched to identify oncology patients who had received a prescription for a DOAC (rivaroxaban or apixiban). Sixtyfive patients were identified and case records were then examined for evidence of venous thromboembolism. Results: Five seperate episodes of recurrent venous thromboembolism were identified in four patients in our cohort., one patient having two seperate episodes of pulmonary embolus. All were on recommended therapeutic doses of DOAC at the time of thromboembolic event. Two patients experienced proven pulmonary embolus on CT pulmonary angiography (1 twice), one lower limb deep vein thrombosis and one upper limb deep vein thrombosis. Conclusions: This retrosepctive review reinforces the clinical guidelines stated by the Cochrane review and ASCO that LMWH should always be first line for the initial and continuation treatment of a VTE. The guidelines did not focus on the suboptimal anticoagulation aspect of the newer oral anticoagulants but more on the safety issues. Research has been mainly focused on comparing LMWH with unfractionated heparin (UFH) or oral warfarin. Comparisons between DOAC versus Warfarin as an oral form of therapy have also been made. In the available published literature, there is a paucity of research comparing DOACs to LMWH. We have identified four patients out of sixtyfive treated with therapeutic doses of DOAC who developed subsequent thromboembolism. This is additional supportive evidence that newer oral anticoagulant agents may not be efficacious in malignancy driven VTE and that LMWH should remain the standard of care. Patients specifically requesting DOAC for cancer associated VTE should be made aware of this data.