Documenting the complete resolution rates of venous thromboemboli (VTE) with the factor Xa inhibitor fondaparinux sodium (FS) in patients with cancer.

Abstract

9130 Background: Cancer patients have a significant risk of VTE. Recurrent VTE rates of 9-17% occur (Lee NEJM 2003) despite the use of therapeutic anticoagulation (AC). Low molecular weight heparins (LMWH) afford several advantages over warfarin. Nevertheless, even with LMWHs more than 20% of patients have VTE propagation. Completeresolution and partial resolution of DVTs occur in up to 38% and 54%, respectively, after 6 months of AC (Prandoni Ann Intern Med 2002, Piovella Haematologica 2002), and thrombi remaindetectable in half of non-cancer patients after a year (Kearon Circulation 2003). Recently, Factor Xa inhibitors have become available and require further study to determine if they offer therapeutic improvements in this patient population. As part of the CAT (Cancer and Thrombosis) trial, we prospectively evaluated complete resolution rates with the Factor Xa inhibitor fondaparinux sodium (FS). Methods: Inclusion criteria included an acute VTE (DVT and/or PE) in patients with cancer and creatinine clearance > 30 mL/min. Patients received FS [5mg SC for pts <50 kg or age >65, 7.5mg SC for pts 50–100 kg and 10mg SC for pts >100 kg]. Imaging studies after baseline were repeated on days 14, 30, and 56 for DVTs, and on day 56 for PEs. Results: 64 patients were entered and 63 evaluated. Cancer types included: Lung (25%); Breast (18%), Colon (14%), Pancreas (14%), Lymphoma (8%), Ovarian (6%), and 15% with other cancers. Findings included: 107 DVT sites and 43 PEs. No patient had a recurrent DVT; 2 (3%) patients had new asymptomatic PEs. Major bleeding occurred in 3 patients (5%); minor bleeding occurred in 4 patients (6%). VTE resolution results are seen in the table. Conclusions: 1) The VTE complete resolution rate documented in this prospective trial with FS is among the highest reported in patients with cancer, and occurred within 8 weeks of starting AC. 2) VTE resolution could help tailor the duration of AC. These favorable results support future randomized trials to compare resolution rates of FS with LMWHs, and to evaluate if the optimal duration of AC depends on VTE resolution. % with complete resolution day 56 (95% CI) DVTs (n=107) 51% (40.6%-60.3%) PEs (n = 43) 47% (31.2%-62.3%)