Expanded Window of Stroke Thrombectomy With Simpler Imaging

Conflicting Results on Shift Analysis

The primary outcome was a shift analysis of the modified Rankin Scale (mRS) disability score at 90 days.

This showed a bidirectional result, with thrombectomy increasing the chances of a good or excellent outcome (mRS, 0-3), but there was also a nonsignificant increased risk for a bad outcome (mRS, 5-6).

“This bidirectional result prevents a common odds ratio from being calculated, so the primary endpoint is not applicable,” Dr. Nogueira reported.

The researchers therefore used the secondary outcomes as the main results of the study.

These showed that the number of patients achieving a good outcome (mRS, 0-2) was significantly increased with thrombectomy (25% vs. 14%, adjusted odds ratio, 2.56; P = .012).

The number of patients achieving an excellent outcome (mRS, 0-1) was also significantly increased.

But these increases in good outcomes came at the cost of some patients having an increased risk for severe disability or death (mRS, 5-6).

The odds ratio for an mRS of 0-4 versus 5-6 was 0.71, and for an mRS of 0-5 versus 6, the odds ratio was 0.58. Both these results were nonsignificant.

Another anomaly in the RESILIENT-Extend trial was the observation of no benefit of thrombectomy seen in older patients.

“In general, trials of thrombectomy in the first world have shown a greater treatment effect in older patients, but this was not seen in our trial, where older patients (over 68 years) did not derive any benefit from the procedure,” Dr. Nogueira noted.

A similar observation was also seen in the first RESILIENT trial in patients treated within 8 hours of stroke onset, which was also conducted in Brazil, leading to the suggestion that it is related to the patient population included.

“In the Brazilian public health service, older patients are very vulnerable and frail. They are different to older patients in first world countries. It appears they may be too fragile to withstand the thrombectomy process,” Dr. Nogueira said.
 

Frailty: A Ceiling Effect?

Results from the two RESILIENT trials give a word of caution to the thrombectomy field, Dr. Nogueira said.

“This procedure was initially thought suitable only for patients with small core strokes, but we now have a series of trials showing benefit of thrombectomy in large core strokes as well,” Dr. Nogueira said. “We have started to believe that this intervention will benefit almost all patients with large vessel occlusion stroke everywhere around the world, but our data suggest that we have to consider the specific populations that we are serving and that factors such as socioeconomic status and frailty have to be taken into account.

“Both the RESILIENT trials have shown that thrombectomy does not appear to be suitable for older patients, over 68-70 years of age, in the public health service in Brazil,” he noted. “In this population, a patient aged 70 can be quite different to a patient of the same age in a first-world country. I think in our population, an age of over 68-70 is a surrogate for frailty, which will not be the case in first-world countries. In this regard, I think we have found a ceiling effect for benefit of thrombectomy, which is frailty.”

Dr. Nogueira speculated that the bidirectional effect on the mRS shift analysis may also have been caused by the frailty of some of the patients.

“What the results may be showing is that for most of the population, there is a benefit of thrombectomy, but for some patients, possibly the most frail, then the procedure can be too overwhelming for them. But the suggestion of harm was not significant, so this observation could have also just been the play of chance,” he added.