Understanding burden of proof and equipoise in the design of pragmatic clinical trials: An example from a trial on brain arteriovenous malformations

Understanding how the research question impacts trial design: Examples from discectomy trials

BACKGROUND

Formulating a pertinent research question is of the utmost importance in clinical research. An ill-conceived question may lead to an erroneous trial design, which may adversely affect the care of patients and provide uninformative or even misleading results.

METHODS

We review the research question of a randomized trial on the timing of lumbar discectomy. We compare the resulting design with other trials, real or hypothetical, that would have been more appropriate.

RESULTS

The RCT we examine randomly allocated patients to early or delayed surgery to answer a theoretical question of the effect of time on the efficacy of surgery. The trial was interpreted to have shown that early surgery was associated with better clinical and functional outcomes as compared to delayed surgery. This conclusion is clinically misleading. Valid comparisons between groups should be performed on intent-to-treat analyses and at the same time points after randomization (and not at a fixed follow-up period after surgery). The clinically pertinent comparison is not between the theoretical efficacy of surgery performed at various times, but between surgery and conservative management in patients presenting at various times. Better-designed trials on the clinical benefits of lumbar discectomy, including the treatment of chronic sciatica, have been published.

CONCLUSION

Theoretical research questions inspired from observational data can lead to erroneous trial design. Prospective randomized trials impact practice immediately: they are unique occasions to address clinical problems and optimize care under uncertainty in real time. However, they require the research question to be formulated with great care.

Patient Selection in a Pragmatic Study on the Management of Patients with Brain Arteriovenous Malformations

BACKGROUND

The Treatment of Brain Arteriovenous Malformations Study (TOBAS) is an all-inclusive pragmatic study comprising 2 randomized clinical trials (RCTs). Patients excluded from the RCTs are followed in parallel treatment and observation registries, allowing a comparison 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 observation 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 radiosurgery (n = 13). Pre-embolization was considered for 179/309 (58%) patients allocated/assigned to surgery or stereotactic 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.

Understanding the problems with recruitment in surgical randomized trials: A lesson from landmark trials on temporal lobe epilepsy

BACKGROUND

Surgical randomized trials are difficult to accomplish. One major problem is recruitment of a sufficient number of patients to address the clinical problem.

METHODS

We review the various ways patient recruitment in surgical RCTs can be promoted. We examine two landmark trials on the surgical treatment of temporal lobe epilepsy (TLE), one that was successful, and one which did not attain the target number of participants.

DISCUSSION

Both designs of the Canadian and American trials of surgery for TLE included a benefit to participants: the Canadian trial gave a chance to have immediate access to investigation and treatment, as compared to a 1 year delay (considered 'standard care' in that center), while the American trial offered free surgical management to both arms. Patients were recruited and treatments randomly allocated prior to knowing for certain whether they were surgical candidates or not. This design choice may have helped circumvent the 'equipoise problem'. The Canadian trial offered participation to drug-resistant patients that were already routinely referred to surgical centers, while the success of the American trial which limited recruitment to the early period of drug resistance was dependent on a change of practice of referring clinicians which did not materialize.

CONCLUSION

The surgical treatment of drug-resistant temporal lobe epilepsy has been validated using RCT methods. Ways to promote participation in surgical trials should be further investigated.