Influence Of Active Cancer On The Efficacy and Safety Of Dabigatran Versus Warfarin For The Treatment Of Acute Venous Thromboembolism: A Pooled Analysis From RE-Cover and RE-Cover II

In two phase III trials, RE-COVER and RE-COVER II, dabigatran etexilate was as effective as warfarin for treatment of acute venous thromboembolism (VTE), with a lower risk of bleeding. Cancer and its treatments are risk factors for VTE and bleeding.

We performed a prespecified subgroup analysis on pooled data from RE-COVER and RE-COVER II to investigate the efficacy and safety of dabigatran versus warfarin in patients with and without active cancer at any time during the study. Active cancer was defined as: a diagnosis of cancer (other than basal-cell or squamous-cell carcinoma of the skin) within 5 years before enrolment; any treatment for cancer within 5 years before enrolment; or recurrent or metastatic cancer.

Patients with acute VTE received parenteral anticoagulation and were randomized to the addition of warfarin or warfarin-placebo for at least 5 days until the international normalized ratio (INR) was ≥ 2 at two consecutive measurements. This was followed (on discontinuation of parenteral therapy) by continued warfarin (target INR range 2.0–3.0) or dabigatran 150 mg twice daily (double dummy; “oral only” treatment period) for 6 months. Primary efficacy outcome: recurrent, symptomatic, objectively confirmed VTE or VTE-related death from randomization (i.e., start of parenteral therapy plus either warfarin or warfarin-placebo) up to the end of the prespecified post-treatment follow-up. Safety: major bleeding events (MBEs), the composite of MBEs or clinically relevant bleeding events (CRBEs), and any bleeds, measured from the start of the double-dummy period (treatment with oral dabigatran or warfarin alone) up to the end of the 6-month study period. Thus, the safety analysis excludes events associated with parenteral therapy either in combination with warfarin or with warfarin-placebo prior to commencing dabigatran treatment; it therefore compares dabigatran with warfarin at its full pharmacological potential.

Overall, recurrent VTE or VTE-related death occurred in 68/2553 patients (2.7%) randomized to dabigatran and 62/2554 (2.4%) randomized to warfarin; hazard ratio (HR) 1.09 (95% confidence interval [CI] 0.77, 1.54). The Table shows event rates for dabigatran versus warfarin in subgroups with and without active cancer at any time. Cox regression analysis showed that presence of cancer was associated with a statistically significant increase in the likelihood of VTE or VTE-related death. However, there was no significant interaction with treatment, indicating similar treatment effects regardless of the presence or absence of active cancer. Overall, MBEs were significantly less frequent with dabigatran than with warfarin during the oral treatment only (double dummy) period (HR 0.60; 95% CI 0.36, 0.99). Likewise, the MBE/CRBE incidence overall was significantly lower with dabigatran versus warfarin overall (HR 0.56; 95% CI 0.45, 0.71). Results according to cancer status are shown in the Table. Patients with cancer had significantly higher rates of MBEs and MBEs/CRBEs than those without. There was no significant treatment interaction by cancer status for MBEs, whereas the treatment interaction for MBEs/CRBEs was significant (p = 0.0257) with a lower rate of bleeding with dabigatran versus warfarin in patients without compared to with cancer. Any bleeding events were significantly less frequent with dabigatran than with warfarin overall, and showed no significant treatment interaction with cancer status.

There was a significantly higher frequency of recurrent VTE or VTE-related mortality among patients who had cancer, but the efficacy of dabigatran versus warfarin was similar irrespective of cancer status. The incidence of bleeding events was similar or numerically lower with dabigatran than with warfarin across cancer subgroups.

Schulman:Boehringer Ingelheim: Consultancy, Honoraria, Research Funding; Bayer Healthcare: Consultancy, Honoraria, Research Funding. Off Label Use: Dabigatran etexilate is an oral direct thrombin inhibitor approved for the prevention of stroke in patients with atrial fibrillation and (outside the US) for prevention of venous thromboembolism in patients undergoing total hip or knee replacement. This presentation includes discussion of the following off-label use of dabigatran: treatment of venous thromboembolism. Eriksson:Boehringer Ingelheim: Consultancy; BMS: Consultancy; Pfizer: Consultancy. Goldhaber:Boehringer Ingelheim: Consultancy; Daiichi: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Pfizer: Consultancy; Portola: Consultancy; Sanofi-Aventis: Consultancy. Kakkar:Boehringer Ingelheim: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Daiichi: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Eisai: Consultancy, Honoraria, Research Funding. Kearon:Bayer Healthcare Inc.: Consultancy; Boehringer Ingelheim (Canada) Ltd./Ltée: Consultancy. Schellong:Boehringer Ingelheim: Advisory Boards Other, Consultancy, Honoraria; Bayer Healthcare: Advisory boards, Advisory boards Other, Consultancy, Honoraria; BMS/Pfizer: Honoraria; Daiichi Sankyo: Advisory Boards, Advisory Boards Other, Honoraria. Feuring:Boehringer Ingelheim: Employment. Peter:Boehringer Ingelheim: Employment. Friedman:Boehringer Ingelheim: Employment.