EVAR trial results don't sync with real-world outcomes

Endovascular aneurysm repair (EVAR) has a lower 30-day mortality rate than open abdominal aortic aneurysm (AAA) surgery in trials, but rates may not be as low in a real-world setting. Researchers who compared findings from a national clinical database against a recent trial believe the difference may be in the patient cohort’s pre-existing health status.

In a study published online Oct. 22 in JAMA: Surgery, researchers noted that EVAR conferred a 70 percent reduction in 30-day postoperative mortality as opposed to open AAA repair, but mortality rates were still higher in a real-world clinical cohort than reported in randomized clinical trials.

Mahmoud Malas, MD, MHS, of the vascular surgery division at the Johns Hopkins Medical Institutions in Baltimore, and colleagues analyzed the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) data for patients with AAA. The prospective NSQIP data encompassed patients who received treatment across the U.S. in a real-world practice setting. The data were then compared against findings from the Open Vs. Endovascular Repair (OVER) Veterans Affairs Cooperative trial.

Patients in the OVER trial were treated between 2002 and  2008. Malas et al looked at NSQIP patients from 2005 through 2011 to allow overlap in procedure innovation, expertise and acceptance.

They found that 25.1 percent of patients in NSQIP had open repair, while 74.9 percent underwent EVAR. More women were part of the NSQIP dataset and more patients had complex comorbidities and worse American Society of Anesthesiologists classification. These patients had poorer outcomes. The OVER cohort, derived from veterans, was largely male with fewer comorbid conditions.

For 30-day mortality, OVER reported 0.2 percent rate for EVAR and 2.3 percent for open repair. However, the research team found that even excluding female patients, 30-day mortality among patients in NSQIP was 1.2 percent for EVAR and 3.3 percent for open repair.

Men had a lower risk of death compared with women (odds ratio: 0.73) and patients with significant morbidities had a nearly eight-fold higher risk of operative mortality (adjusted odds ratio: 7.81). 

Malas et al noted that EVAR has increasingly become the go-to procedure. In 2005, 65 percent of AAA procedures performed were EVAR; by 2011, surgeons performed EVAR in 80 percent of cases.

Because risk was so much greater among the general population undergoing AAA surgery, Malas et al found that mortality rates did not change over time and EVAR mortality rates did not drop. They posited that it was also this higher level of risk that accounted for the difference seen in mortality rates between patients in the OVER study compared with the NSQIP dataset.

“While the OVER trial is useful in identifying differences between EVAR and open repair, results from our real-world analyses pose a better reference for prognosis, with emphasis on the need for patient specific risk assessment and treatment,” Malas et al wrote.