IMS 3 Stroke Study Shows Lack of Benefit for tPA Plus Endovascular Therapy Versus tPA Alone

February 7, 2013—The American Stroke Association (ASA) announced that results from the Interventional Stroke Management III trial (IMS 3) showed that adding endovascular therapy to clot-busting therapy for stroke did not significantly improve stroke recovery at 3 months. The data were presented in a special symposium at the ASA's International Stroke Conference 2013 in Honolulu, Hawaii.

According to the ASA, the study investigators found that the lack of benefit was despite an approximately 40% greater likelihood of reopening blocked arteries and improving blood flow to the brain with endovascular treatment added to intravenous (IV) treatment with tissue plasminogen activator (tPA).

The IMS 3 trial was funded by the National Institutes of Health and led by Joseph P. Broderick, MD, the primary neurologist investigator, and Thomas A. Tomsick, MD, the primary interventional investigator. Both Dr. Broderick and Dr. Tomsick are affiliated with the University of Cincinnati Academic Health Center in Ohio.

Dr. Broderick, who is Professor and Chair of the Department of Neurology and Rehabilitation Medicine at the University of Cincinnati College of Medicine, commented in the ASA press release, “This is an important finding, whether or not patients are eligible for IV tPA. Endovascular treatment remains an important option for acute stroke, since some patients with large intracranial occlusions cannot receive IV tPA during the 4.5-hour time window from stroke onset in which IV tPA is used. However, we need additional trials to better define the use of endovascular therapy.”

The ASA advised that the researchers had been hopeful that clearing vessel blockages with endovascular therapy would improve recovery from stroke. IV tPA is the only emergency stroke treatment proven to improve recovery. It must be given within 4.5 hours of symptom onset, and faster start of treatment with IV tPA leads to better recovery.

In the IMS 3 trial, 656 patients received IV tPA within 3 hours of stroke onset and 423 were randomized to receive endovascular therapy in addition to IV tPA if a clot was revealed at angiography. The investigators compared 90-day recovery of the IV tPA-plus-endovascular-treatment group to the IV tPA-only group to determine if patients recovered functional independence (a modified Rankin score of 2 or lower).

As summarized in the ASA press release, the IMS 3 investigators found that no statistical difference in the proportion of patients achieving functional independence occurred between the two groups (40.8% of those receiving both therapies vs 38.7% of those receiving IV tPA only). Patients with the most severe strokes and those with more rapid treatment tended to have better outcomes with endovascular treatment, but the differences were not significant. Death rates and bleeding in the brain that worsened the patients' clinical condition were similar for endovascular-therapy and tPA-only groups. The investigators ended the multicenter international trial early, with about two-thirds of planned participants enrolled. The trial was stopped in April 2012 after an interim analysis determined the additional therapy was highly unlikely to benefit patients. The investigators suggested that a larger trial of patients with severe strokes and larger artery occlusions might show an effective use for endovascular therapy, stated the ASA.