Recurrent venous thromboembolism in cancer patients treated with direct oral anticoagulants.

Abstract

e13648 Background: Malignancy associated thrombosis places a significant clinical and financial burden on all major oncology services worldwide. Cancer patients are at an increased risk of thrombosis and large studies have suggested a subsequent increased mortality. (1) Some studies have recorded higher risk associated with certain chemotherapy regimens such as platinum-based agents and gemcitabine. (2) Guidelines for anticoagulation often recommend low molecular weight heparin (LMWH) as first line for malignancy associated thrombosis. (3) In recent years ASCO guidelines have added DOACs as an option for VTE treatment. (4) We herein describe eight cases of recurrent venous thromboembolism despite direct oral anticoagulation. Methods: Data was gathered from electronic patient records for cancer patients attending a single centre in Western Australia between 2016 and 2021. Radiology and medication records were used to confirm VTE diagnoses and subsequent treatment. This data was recorded on an excel file and analysed accordingly. Results: We identified 8 patients with recurrent VTE on DOACs. Median age of patients was 61 years (range 50-72). The most common associated malignancy was pancreatic cancer (n = 3). Other associated cancer types were ovarian (n = 2), lung adenocarcinoma (n = 2) and colorectal cancer(n = 1). Most patients had metastatic disease at time of first VTE(n = 5). The most common site of thrombosis was in the upper limb with 3 cases of initial VTE and 4 cases of recurrent VTE. All of these occurred in patients with peripherally inserted central catheters. (PICC) One patient had a left central retinal vein thrombosis resulting in complete loss of vision in that eye. All but one patient had received either platinum based chemotherapy or gemcitabine. Median time to initial thrombotic event was 4 months from diagnosis. Median time to recurrent thrombotic event was 3.5 months. Rivaroxaban was the most common DOAC used with initial VTE (n = 5). All other patients received apixaban (n = 3). All patients were switched to either LMWH (n = 6) or unfractionated heparin (n = 2) following recurrent VTE. 75% of patients did not have further thrombosis after switch to heparin. One patient had chronic thrombosis on subsequent scans and another patient had recurrent pulmonary embolism despite unfractionated heparin and vena cava filter insertion. Conclusions: Venous thromboembolism is a common complication of malignancy with significant associated morbidity and mortality. A high index of suspicion is needed in patients with clinical signs of recurrent VTE while on a DOAC, especially for those with PICCs. While DOACs are common for patient preference, the differing rates of VTE recurrences should be further investigated and considered in oncology prescribing practice going forward.