Of all the sentences you never want to read from scientists running a study of a promising new medical treatment, high on the list has got to be, “the trial was terminated early for futility.”
Yet there it is, describing what happened when researchers assessed a surgical procedure that had “slam dunk” written all over it. The idea was to take patients who had complete blockages of the internal carotid artery, which carries blood to the brain, with the not-surprising result that they had insufficient blood flow to the brain. The patients had also had at least one transient ischemic attack (TIA), or “mini-stroke,” as a result of blood supply to a part of the brain being temporarily reduced or blocked altogether. Half the patients in the study received standard medical treatment, such as aspirin and other anti-clotting drugs plus anti-hypertension drugs, while the other half got the promising surgery: bypassing the blocked carotid, in the neck, with an artery in the scalp. Surely, went the rationale, steering blood around a blockage would lower the subsequent stroke rate. Expectations were high: leaders of the Carotid Artery Occlusion Surgery Study (COSS) projected that there would be 40 percent fewer strokes on the same side as the blockage in patients who had the surgery.
The experimental surgery was nifty but not effective.
Courtesy of Powers, et al., and JAMA
Not so much. In yet another example of how human biology continues to thwart what seems like compelling medical logic (more on which below), the 97 patients receiving the surgery had no fewer strokes than the 98 receiving standard medical care, the COSS team reports in the Journal of the American Medical Association. Things began to go south early. After one month, 14 of the 97 surgery patients had another stroke, compared to 2 of 98 controls. After 2 years, things merely evened out: 20 patients in each group had had a stroke. (A 1985 trial of the surgery had also shown no benefit, in 808 patients.) At that point, the Data Safety Monitoring Board advised halting the trial, which was done in June 2010. (It seems small comfort that if you survived your first month post-surgery without a stroke, your risk of subsequent stroke fell by about 75 percent.) Bypass, concluded the COSS researchers, “provided no additional benefit over medical therapy for preventing recurrent stroke.”