SAN DIEGO – Prophylaxis with rivaroxaban achieved significant reductions in venous thromboembolism, compared with two commonly used drugs when put to the test in 5,346 consecutive, unselected patients undergoing major orthopedic surgery.
The incidence of in-hospital symptomatic venous thromboembolism (VTE) was 2.4% with rivaroxaban (Xarelto), compared with 3.9% with low molecular weight heparin (LMWH), and 5.5% with fondaparinux (Arixtra). This corresponds to a relative risk reduction of 39%, compared with LMWH, and 57% compared with fondaparinux.
Rivaroxaban, an oral Factor Xa inhibitor, also has superior safety with regard to major bleeding and surgical complications, according to Dr. Jan Beyer-Westendorf, with the University Clinic at Dresden (Germany) Technical University.
"Patients in real-world major orthopedic surgery benefit from VTE-prophylaxis with rivaroxaban even more than could be expected from the phase III results of the RECORD trial," he said at the annual meeting of the American Society of Hematology.
The four phase III RECORD (REgulation of Coagulation in ORthopedic Surgery to Prevent Deep Vein Thrombosis and Pulmonary Embolism) trials compared rivaroxaban with enoxaparin in more than 12,500 patients undergoing knee and hip replacement. The trials did not evaluate fondaparinux or LMWH, despite being the standard of care at many hospitals.
Rivaroxaban was approved in the United States in July 2011 for DVT prophylaxis in adults undergoing hip and knee replacement surgery, and gained a second indication in November 2011 for stroke prophylaxis in patients with nonvalvular atrial fibrillation.
Dr. Beyer-Westendorf and his colleagues analyzed 5,346 consecutive patients who underwent major orthopedic surgery at the university clinic during three periods: 2005-2007 when LMWH was the standard prophylaxis; 2008-2009 when fondaparinux was the standard; and finally from 2010 to June 2011 when rivaroxaban became the clinic’s standard prophylaxis.
In all, 1,055 patients were treated with rivaroxaban, 1,683 with LMWH, and 2,069 with fondaparinux. Of note, previous VTE was more common at baseline in the rivaroxaban group at 4% vs. 1.4% in the LMWH group, and 1.1% in the fondaparinux group, he said.
Rivaroxaban reduced the relative risk of the composite of proximal DVT, pulmonary embolism, and VTE-related death by 29%, compared with LMWH, and 42% compared with fondaparinux, but the difference between the three groups did not achieve statistical significance (1.0% vs. 1.4% vs. 1.7%), Dr. Beyer-Westendorf said.
In a pooled analysis of RECORD 1, 2, and 3, rivaroxaban significantly reduced the composite of symptomatic VTE and all-cause mortality during the 2-week period after surgery, compared with enoxaparin (0.4% vs. 0.8%), according to the Bayer HealthCare website.
In the current analysis, severe bleeding was significantly lower with rivaroxaban at 7.4% vs. 14.9% with LMWH, and 11.1% with fondaparinux.
Bleeding leading to surgical revisions was also significantly lower at 0.4% vs. 1.7% with LMWH, and 1.1% with fondaparinux.
Dr. Beyer-Westendorf pointed out that severe bleeding rates were less than 1% in the RECORD 1-4 trials using a more narrow definition of severe bleeding as overt bleeding outside of the surgical site. Their analysis used the International Society on Thrombosis and Hemostasis criteria for severe bleeding.
Finally, the reduction in VTE events, bleeding, and surgical revisions was correlated with a significantly shorter median hospital stay in patients given rivaroxaban prophylaxis vs. LMWH or fondaparinux (8.3 days vs. 11.6 days vs. 9.3 days).
Dr. Beyer-Westendorf said it was unlikely that changes in anesthesia or surgical practice over the study period could have attenuated the results. In addition, the researchers conducted a matched-pair analysis to evaluate whether the benefits of rivaroxaban were due to selection or detection bias. Outcomes remained superior for rivaroxaban after matching patients according to age, gender, type of surgery, and history of VTE. Complete compression ultrasound testing also remained constant at about 13% from 2005 to 2010 before falling to 8.2% in 2011 due to fewer complete compression ultrasound–positive findings, Dr. Beyer-Westendorf noted.
"These findings in a large real-world surgery cohort are robust and not significantly influenced by a selection or detection bias," he said.
Dr. Beyer-Westendorf disclosed research grants from and serving as a speaker for Bayer HealthCare, which markets Xarelto.