Sara Hassani, MD, MHS
The ROADSTER II article, which follows its predecessor, the ROADSTER I study from 2015,1 recently published results in the September 2020 issue of Stroke. The article demonstrates some promising outcomes with regard to peri-procedural stroke rates when performing TransCarotid artery revascularization (TCAR).
TCAR represents a novel technique different from the established methods of carotid revascularization — namely, transfemoral stenting or carotid endarterectomy (CEA). With TCAR, the emphasis is on a transcarotid approach to stenting, and, additionally, there is a protection mechanism deployed to prevent cerebral embolization. The major Achilles heel of traditional transfemoral carotid artery stenting (tfCAS), known from prior studies (CREST,2 SPACE3), is the higher peri-procedural risk of stroke in comparison with CEA, and, unfortunately, distal filter placement during tfCAS has failed in the past to demonstrate convincing efficacy at lowering rates of peri-procedural stroke. TCAR differs importantly from tfCAS in that the operator avoids navigating the aortic arch, a known key source of embolization and subsequent stroke, particularly in elderly patients. The mechanism of neuroprotection with TCAR is with the use of an extracorporeal reversal flow system, and also clamping of the carotid artery below the sheath insertion, which leads to obligate reversal flow in the carotid system during the case. The protection groundwork is laid before any intervention is done; before a wire even crosses the lesion, reversal flow is achieved so that debris is trapped and removed via the system, and the blood is given back in the femoral vein.
With respect to procedure, TCAR requires a direct transcarotid cut down, low in the neck in the common carotid artery. There are certain technical/surgical nuances to securing the artery and positioning the sheath. The single most essential surgical or anatomic consideration with respect to determining candidacy for the procedure is the requirement for a certain length of reasonably disease-free common carotid artery in order to access the artery and position the sheath.
ROADSTER II was a prospective, single-arm, multi-center study designed to assess the usage of the ENROUTE Transcarotid Stent when used with the ENROUTE Transcarotid Neuroprotection System (developed by Silk Road Medical, Inc.) by physicians of varying experience with the TCAR procedure.
The primary endpoint of the ROADSTER II study was procedural success (technical success + absence of stroke, myocardial infarction (MI), or death within the thirty-day post-operative period). 692 patients with either symptomatic (over 50% stenosis) or asymptomatic carotid disease (more than 80% stenosis) were enrolled (632 adhered to protocol).
The reported results from the ROADSTER II study (with a much larger cohort than in the previous ROADSTER I study) are compelling, and likely represent the lowest peri-op stroke rate ever reported in a prospective carotid revascularization study. The thirty-day stroke rate was only 1.9% (thirteen patients), and death rate was 0.4% (three patients), and so the composite was 2.3%. In the population that adhered to the protocol (n=632), there were strokes in only four patients (0.6%). In comparison, the thirty-day stroke rate for tfCAS from CREST2 was notably higher at 4.1%, and 2.3% for CEA.
Another positive finding from the ROADSTER II article was the reported lower rate of acute and persistent cranial nerve injury (1.4%) than was observed for patients that underwent CEA in the landmark CREST study (4.8%).2
While the reported results from this article are promising, there are a few limitations to note. First of all, we need to encourage caution in interpreting single-arm, non-randomized data. Secondly, longer term follow-up data to confirm these early TCAR stroke outcomes is clearly lacking at this point. A robust amount of data from prior randomized trials (such as CREST),2 evaluating and comparing tfCAS and CEA, have clearly established that these two procedures are equivalent and effective in terms of long-term stroke outcomes (CEA, 6.8% and tfCAS, 7.2%) at the four-year mark. Third, the patients included in the ROADSTER study were predominately and disproportionately asymptomatic (had never had a focal neurologic deficit), as only 16% of the included patients had had a TIA or minor stroke.
One additional point to mention is that not all patients requiring carotid revascularization will qualify for TCAR based on the anatomic requirements that need to be met (described above), and these patients would still ultimately need a CEA. Finally, one other concern with regard to candidacy is that reversal of flow in these TCAR cases is dependent on an adequate collateral system, and patients with moderate or severe intracranial atherosclerotic disease may have diminished collateral flow that may be compromised during the procedure.
All in all, however, for those patients that qualify, TCAR seems to have convincingly carved out a niche in our arsenal of options for carotid revascularization. The ROADSTER II study demonstrates promising outcomes with regard to peri-procedural stroke rates with TCAR. TCAR is here to stay, and we are likely at the point now where a prospective randomized, controlled trial with three arms comparing TCAR with tfCAS with CEA peri-op and long-term stroke rates is warranted.
References:
1. Kwolek CJ, Jaff MR, Leal JI, Hopkins LN, Shah RM, Hanover TM, Macdonald S, Cambria RP. Results of the ROADSTER multicenter trial of transcarotid stenting with dynamic flow reversal. J Vasc Surg. 2015 Nov;62(5):1227-34.
2. Brott TG, Hobson RW 2nd, Howard G, Roubin GS, Clark WM, Brooks W, Mackey A, Hill MD, Leimgruber PP, Sheffet AJ, Howard VJ, Moore WS, Voeks JH, Hopkins LN, Cutlip DE, Cohen DJ, Popma JJ, Ferguson RD, Cohen SN, Blackshear JL, Silver FL, Mohr JP, Lal BK, Meschia JF; CREST Investigators. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med. 2010 Jul 1;363(1):11-23.
3. Eckstein HH, Ringleb P, Allenberg JR, Berger J, Fraedrich G, Hacke W, Hennerici M, Stingele R, Fiehler J, Zeumer H, Jansen O. Results of the Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) study to treat symptomatic stenoses at 2 years: a multinational, prospective, randomised trial. Lancet Neurol. 2008 Oct;7(10):893-902.
