Conference Coverage

Late thrombectomy for stroke has low number needed to treat for benefit



– The number of ischemic stroke patients with a clinical core mismatch showing salvageable tissue who need to be treated with thrombectomy to obtain a significant benefit on functional outcomes is just 2 when the time frame from last known well extends out to 24 hours, according a subanalysis of results from the DAWN trial.

The Jan. 4, 2018, publication of the DAWN trial revealed that patients with ischemic strokes can benefit from thrombectomy long after the time window generally thought to afford benefits had closed (N Engl J Med. 2018;378:11-21). The procedure yielded significant benefits in functional outcomes at 90 days in patients with a clinical core mismatch showing salvageable tissue.

Dr. Jeffrey L. Saver, professor of neurology, UCLA Mitchel L. Zoler/Frontline Medical News

Dr. Jeffrey L. Saver

The subanalysis of the trial, presented at the International Stroke Conference, revealed that the number needed to treat (NNT) was just 2 to achieve a 1-point reduction in the modified Rankin Scale (mRS) score at 90 days. The NNT ranged as high as 19 to achieve normal functioning, defined as an mRS score of 0.

The results are important because health care systems must now make decisions about allocating resources for the treatment of these patients, which will include installing imaging techniques and expertise at various centers. “It will be practical in some primary stroke centers and not in others. We’re going to see a lot of interesting research about what frontline hospitals should do. There are lots of options at that screening step, and we’re going to need experience to see what’s best. It won’t be the same answer for everyone,” Jeffrey Saver, MD, said during a press conference announcing the results at the meeting, which was sponsored by the American Heart Association. Dr. Saver is director of the stroke unit at the University of California, Los Angeles, and professor of clinical neurology at the university.

The DAWN trial randomized 206 patients to thrombectomy plus standard care or standard care alone. The study was halted at an enrollment of 206 patients because of overwhelming efficacy. To be eligible, the patients had to have a mismatch between the severity of clinical deficit and the infarct volume as measured via automated analysis (RAPID software, SchemaView) of diffusion-weighted MRI or perfusion CT. They had to have substantial clinical deficits, but limited infarct size, with specific criteria varying with age, National Institutes of Health Stroke Scale score, and infarct size.

The NNT for an mRS score of 0 (asymptomatic) was 19. For freedom from disability (mRS, 0-1), the NNT was 4. For functional independence (mRS, 0-2), it was 3. To achieve ambulatory status (mRS, 0-3), it was 3. To avoid a requirement for constant care (mRS, 0-4), the NNT was 9.

To achieve any reduction in disability at all, the NNT was 2. This value was identical when looking at patients in the 6- to 12-hour window and those in the 12- to 24-hour window. However, the nature of the benefit was different. “In the late window (12-24 hours), outcomes went from really bad to pretty good. In the early window, it was somewhat bad to very good. So it’s still better to be treated early,” Dr. Saver said.

In short, for every 100 patients treated, 50 would gain an improvement in disability-related quality of life, and 36 would gain functional independence. In the 6- to 12-hour group, 45 of every 100 patients would experience lower disability as a result of treatment, as would 56 of every 100 treated patients in the 12- to 24-hour group.

Stryker Neurovascular funded the study. Dr. Saver has consulted for Stryker and received travel reimbursement.

SOURCE: Saver J et al., ISC 2018 abstract LB3

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