Cancer-Associated Deep Vein Thrombosis: The Role of Residual Vein Thrombosis for Assessing the Duration of Low Molecular Weight Heparin (the EXTENDED Cancer-DACUS)

Introduction. The optimal duration of Low Molecular Weight Heparin (LMWH) after cancer associated deep vein thrombosis (DVT) is unknown; current guidelines suggest to prolong anticoagulation until cancer is active. We have recently demonstrated, in a randomized trial, that detection of Residual Vein Thrombosis (RVT) after 6 months of LMWH identify patients who require or not extension of therapy with anticoagulants (JCO in press). Now we present data of a prospective study evaluating a RVT-based management of patients with cancer-associated DVT, in whom LMWH has been extended up to 2 years in patients considered at high-risk for recurrent DVT because of persistence of RVT.

Material and Methods. Patients were included at the time of a first diagnosis of cancer-associated DVT of the lower limbs. All received LMWH at therapeutic dosage for the first month (approximately 100 UI anti-FXa b.i.d.) then reduced at 75% for the following months. After 6 months of heparin, the presence of RVT was detected: those without RVT (no-RVT group) suspended treatment, while those with RVT (RVT group) continued LMWH for up to 2 years. Recurrent thrombosis and/or bleeding events were recorded during treatment and one year after LMWH withdrawal. Baseline differences between groups were assessed by the chi-square test (Yates’ correction) for categorical variables and ANOVA test or Kruskal-Wallis test for parametric and nonparametric analyses. Relative risks (RRs) and 95% confidence intervals (CIs) were evaluated.

Results. Between January 2009 and April 2011, 211 cancer patients were enrolled; RVT was detected in 129 patients (61.1%). Recurrent VTE occurred in 19 (14.7%); 4 episodes (3.1%) occurred while on heparin. Among patients without RVT (82), 3 (3.6%) developed recurrent VTE (after LMWH therapy). Adjusted HR for RVT vs no-RVT group was 5.8 (95% CI, 1.9 to 19.2; p 0.0003). Three major bleeding events occurred in RVT group and one in no-RVT group (during LMWH administration). The HR for major bleeding (RVT vs no-RVT group) was 2.58 (95% CI, 0.66 to 12.43;p 0.103). Overall, 44 patients (20.8%) died during follow-up as a result of cancer progression.

Conclusions. These results indicate that in patients without RVT, a short period of treatment with a LMWH is sufficient; in those with persistent RVT, treatment extended to 2 years substantially reduces, but does not eliminate, the risk of recurrent thrombosis. However, when still on LMWH, the risk for recurrent VTE is low.