OBJECTIVE Many patients recruited in the Treatment of Brain Arteriovenous Malformations Study (TOBAS) are managed conservatively. The aim of this study was to monitor what happened to those patients. METHODS TOBAS comprises two randomized controlled trials and multiple prospective registries. All patients with brain arteriovenous malformations (AVMs) can participate. This report concerns patients selected for conservative management. The primary trial outcome measure is related death or dependency (modified Rankin Scale [mRS] score > 2) at 10 years. Secondary outcomes include intracranial hemorrhages, nonhemorrhagic neurological events, and serious adverse events (SAEs). For this report, outcome results are presented using patient-years, Kaplan-Meier survival curves, and Cox log-rank tests. There was no blinding. RESULTS From June 2014 to May 2021, 1010 patients were recruited, of whom 498 (49%) were proposed the prospective observation registry. After exclusions, 434 (87%) patients remained for analysis. The majority of patients had unruptured AVMs (378/434 [87%]), of which 195 (52%) were low grade (Spetzler-Martin grade I or II). During a mean follow-up period of 3.2 years (total 1368 patient-years), the primary outcome occurred in 23 of 434 (5%) patients, corresponding to an incidence of 1.7 (95% CI 1.1-2.5) per 100 patient-years. For unruptured AVMs the incidence was 1.1 (95% CI 0.7-1.9) per 100 patient-years, and for low-grade unruptured AVMs it was 0.6 (95% CI 0.2-1.7) per 100 patient-years. Poor outcomes were more frequent in patients with a history of rupture (HR 5.6 [95% CI 2.4-13.0], p < 0.001), infratentorial AVMs (HR 2.9 [95% CI 1.1-7.3], p = 0.027), and age >= 55 years (HR 3.2 [95% CI 1.4-7.6], p = 0.007). Major intracranial hemorrhage occurred in 35 of 434 (8%) patients (incidence of 2.6 [95% CI 1.9-3.6] per 100 patient-years; 2.0 [95% CI 1.3-2.9] per 100 patient-years for unruptured AVMs and 1.3 [95% CI 0.6-2.6] per 100 patient-years for low-grade unruptured AVMs). Major AVM hemorrhages were more frequent in ruptured (HR 4.4 [95% CI 2.1-8.9], p < 0.001), large (HR 2.6 [95% CI 1.1-6.6], p = 0.039), and high-grade (HR 2.5 [95% CI 1.2-5.3], p = 0.013) AVMs and those with deep venous drainage (HR 2.1 [95% CI 1.1-4.2], p = 0.032). SAEs occurred in 48 of 434 (11%) patients (incidence of 3.6 [95% CI 2.7-4.8] per 100 patient-years). For unruptured AVMs the incidence was 2.8 (95% CI 2.0-4.0) per 100 patient-years, and for low-grade unruptured AVMs it was 1.8 (95% CI 1.0-3.2) per 100 patient-years. CONCLUSIONS Nearly half of TOBAS participants were observed. Rates of untoward neurological events were within expected boundaries.

BACKGROUND AND PURPOSE:Flow diversion (FD) has expanded beyond initial indications (proximal carotid artery aneurysms) to include distal circulation aneurysms (on the anterior, middle, or posterior cerebral arteries). Our objective was to examine results obtained from aneurysms in these locations in the Flow Diversion in Intracranial Aneurysm Treatment Trial (FIAT), which compared FD with alternative standard management options (ASMO). MATERIALS AND METHODS:FIAT was an all-inclusive parallel-group 1:1 randomized study comparing FD with 1 of 4 ASMOs (coiling +/- stenting, parent vessel occlusion [PVO], clipping, or observation, prespecified by clinical judgment). The primary safety outcome was death or dependency (mRS >2) at 3 months. The composite primary outcome was "treatment failure," defined as initial failure to treat the aneurysm; aneurysm rupture or retreatment during follow-up; death or dependency (mRS >2); or angiographic residual aneurysm adjudicated by an independent core laboratory at 12 months. This subgroup analysis was not prespecified, and there was no blinding. RESULTS:Of the 323 patients in FIAT, 46 (14%) with distal circulation aneurysms were randomly allocated: 23 to FD and 23 to ASMO (coiling +/- stenting 16 patients; PVO, 1 patient; clipping, 3 patients; and observation, 3 patients). Death or dependency at 3 months occurred in 1 patient (allocated ASMO). Treatment failures occurred in 6/23 FD-treated patients (26.1%; 95% CI, 12.6%-46.5%) compared with 11/22 patients treated with ASMO (50.0%; 95% CI, 30.7%-69.3%) (risk ratio = 0.52 [0.23-1.17]; P = .13). Serious adverse events were similar. CONCLUSIONS:Distal circulation aneurysms treated with FDs in FIAT showed an encouraging trend, but this analysis was underpowered. Further randomized trials are needed.

BACKGROUND: The Treatment of Brain Arteriovenous Malformations Study (TOBAS) is an all-inclusive pragmatic study comprising 2 randomized clinical trials (RCTs). Pa-tients excluded from the RCTs are followed in parallel treatment and observation registries, allowing a compari-son between RCT and registry patients.METHODS: The first randomized clinical trial (RCT-1) offers 1:1 randomized allocation of intervention versus conservative management for patients with arteriovenous malformation (AVM). The second randomized clinical trial (RCT-2) allocates 1:1 pre-embolization or no pre-embolization to surgery or radiosurgery patients judged treatable with or without embolization. Characteristics of RCT patients are reported and compared to registry patients.RESULTS: From June 2014 to May 2021, 1010 patients with AVM were recruited; 498 patients were observed and 373 were included in the treatment registries. Randomized allocation in RCT-1 was applied to 139 (26%) of the 512 patients (including 127 of 222 [57%] with unruptured AVMs) considered for curative treatment. RCT-1 AVM patients differed (in rupture status, Spetzler-Martin grade and baseline modified Rankin Score) from those in the obser-vation or treatment registries (P< 0.001). Most patients had small (<3 cm; 71%) low-grade (Spetzler-Martin I-II; 64%) unruptured (91%) AVMs. The allocated management was conservative (n = 71) or curative (n = 68), using surgery (n = 39), embolization (n = 16), or stereotactic radio -surgery (n = 13). Pre-embolization was considered for 179/ 309 (58%) patients allocated/assigned to surgery or ste-reotactic radiosurgery; 87/179 (49%) were included in RCT-2. RCT-2 patient AVMs differed in size, eloquence and grade from patients of the pre-embolization registry (P < 0.01). Most had small (<3 cm in 82%) low-grade (83%) AVMs in non-eloquent brain (64%).CONCLUSIONS: Patients included in the RCTs differ significantly from registry patients. Meaningful results can be obtained if multiple centers actively participate in the TOBAS RCTs.

OBJECTIVE:The Treatment of Brain Arteriovenous Malformations Study (TOBAS) is a pragmatic study that includes 2 randomized trials and registries of treated or conservatively managed patients. The authors report the results of the surgical registry. METHODS:TOBAS patients are managed according to an algorithm that combines clinical judgment and randomized allocation. For patients considered for curative treatment, clinicians selected from surgery, endovascular therapy, or radiation therapy as the primary curative method, and whether observation was a reasonable alternative. When surgery was selected and observation was deemed unreasonable, the patient was not included in the randomized controlled trial but placed in the surgical registry. The primary outcome of the trial was mRS score > 2 at 10 years (at last follow-up for the current report). Secondary outcomes include angiographic results, perioperative serious adverse events, and permanent treatment-related complications leading to mRS score > 2. RESULTS:From June 2014 to May 2021, 1010 patients were recruited at 30 TOBAS centers. Surgery was selected for 229/512 patients (44%) considered for curative treatment; 77 (34%) were included in the surgery versus observation randomized trial and 152 (66%) were placed in the surgical registry. Surgical registry patients had 124/152 (82%) ruptured and 28/152 (18%) unruptured arteriovenous malformations (AVMs), with the majority categorized as low-grade Spetzler-Martin grade I-II AVM (118/152 [78%]). Thirteen patients were excluded, leaving 139 patients for analysis. Embolization was performed prior to surgery in 78/139 (56%) patients. Surgical angiographic cure was obtained in 123/139 all-grade (89%, 95% CI 82%-93%) and 105/110 low-grade (95%, 95% CI 90%-98%) AVM patients. At the mean follow-up of 18.1 months, 16 patients (12%, 95% CI 7%-18%) had reached the primary safety outcome of mRS score > 2, including 11/16 who had a baseline mRS score ≥ 3 due to previous AVM rupture. Serious adverse events occurred in 29 patients (21%, 95% CI 15%-28%). Permanent treatment-related complications leading to mRS score > 2 occurred in 6/139 patients (4%, 95% CI 2%-9%), 5 (83%) of whom had complications due to preoperative embolization. CONCLUSIONS:The surgical treatment of brain AVMs in the TOBAS registry was curative in 88% of patients. The participation of more patients, surgeons, and centers in randomized trials is needed to definitively establish the role of surgery in the treatment of unruptured brain AVMs. Clinical trial registration no.: NCT02098252 (ClinicalTrials.gov).

OBJECTIVE The management of brain arteriovenous malformations (bAVMs) remains controversial. The Treatment of Brain AVMs Study (TOBAS) was designed to manage patients with bAVMs within a clinical research framework. The objective of this study was to study trial feasibility, recruitment rates, patient allocation to the various management groups, and compliance with treatment allocation. METHODS TOBAS combines two randomized care trials (RCTs) and a registry. Designed to be all-inclusive, the study offers randomized allocation of interventional versus conservative management to patients eligible for both options (first RCT), a second RCT testing the role of preembolization as an adjunct to surgery or radiotherapy, and a registry of patients managed using clinical judgment alone. The primary outcome of the first RCT is death from any cause or disabling stroke (modified Rankin Scale score > 2) at 10 years. A pilot phase was initiated at one center to test study feasibility, record the number and characteristics of patients enrolled in the RCTs, and estimate the frequency of crossovers. RESULTS All patients discussed at the multidisciplinary bAVM committee between June 2014 and June 2016 (n = 107) were recruited into the study; 46 in the randomized trials (23 in the first RCT with 21 unruptured bAVMs, 40 in the second RCT with 17 unruptured bAVMs, and 17 in both RCTs), and 61 patients in the registry. Three patients crossed over from surgery to observation (first RCT). CONCLUSIONS Clinical research was successfully integrated with normal practice using TOBAS. Recruitment rates in a single center are encouraging. Whether the trial will provide meaningful results depends on the recruitment of a sufficient number of participating centers. Clinical trial registration no.: NCT02098252 (clinicaltrials.gov).