Challenges of decision making regarding futility in a randomized trial: the Interventional Management of Stroke III experience

Guidance on interim analysis methods in clinical trials

Interim analyses in clinical trials can take on a multitude of forms. They are often used to guide Data and Safety Monitoring Board (DSMB) recommendations to study teams regarding recruitment targets for large, later-phase clinical trials. As collaborative biostatisticians working and teaching in multiple fields of research and across a broad array of trial phases, we note the large heterogeneity and confusion surrounding interim analyses in clinical trials. Thus, in this paper, we aim to provide a general overview and guidance on interim analyses for a nonstatistical audience. We explain each of the following types of interim analyses: efficacy, futility, safety, and sample size re-estimation, and we provide the reader with reasoning, examples, and implications for each. We emphasize that while the types of interim analyses employed may differ depending on the nature of the study, we would always recommend prespecification of the interim analytic plan to the extent possible with risk mitigation and trial integrity remaining a priority. Finally, we posit that interim analyses should be used as tools to help the DSMB make informed decisions in the context of the overarching study. They should generally not be deemed binding, and they should not be reviewed in isolation.

The INTEND 1 randomized controlled trial of duct endoscopy as an indicator of margin excision in breast conservation surgery

PURPOSE

With early detection, breast conservation surgery with adequate surgical margins is the standard of care. The aim of this study was to evaluate the use of pre-operative duct endoscopy (DE) to target surgical resection, improve adequate margins and reduce re-excision operations.

METHODS

Women with DCIS, stage I and II breast cancer suitable for breast conservation were randomized to DE-assisted wide local excision versus standard wide local excision (without DE). The primary endpoint was margin re-excision rates between the two groups. Secondary end points were: (i) volume differences of the surgical specimen; (ii) whether an extensive in situ component (EIC) influenced successful DE-guided resection.

RESULTS

78 women were randomized: 44 patients to no-DE and 34 patients to the DE group. The median age was 59 (49-65) and 56 (48-64) years in the two groups respectively with mean follow-up of 9.1 (4.2-11.1) years. There were 23 positive findings in 17 women in 30 successful DE procedures (17/30 = 56.7%). The surgical specimen volume, no-DE (17 [IQR 10-29] cm³) and DE 20 [IQR 12-28] cm³), did not differ, p = 0.377. The overall re-excision rate was 20/78 (26%), 9 (20%) and 11 (32% in the no-DE and DE groups, respectively, p = 0.233.

CONCLUSIONS

This randomized clinical trial was limited by incomplete accrual. DE did not contribute to improved margin excision rates whether a target lesion was visualized or not. The presence of EIC did not improve efficacy of DE.

Clinical Results of the Intra-Arterial Thrombolysis with Stent Retriever Device Weather Perfusion Diffusion Mismatching and Intravenous Tissue Plasminogen Activator Administration

Objective

Intraarterial thrombolysis (IA-Tx) with stent retriever is accepted as an additional treatment for selected patients and the clinical benefit is well reported. Each intravenous tissue plasminogen activator administration (IV-tPA) and perfusion diffusion mismatching (P/D-mismatching) is well known the beneficial effects for recanalization and clinical outcomes. In this report, authors analyzed the clinical outcomes of additional IA-Tx with retrieval stent device, according to the combined IV-tPA and P/D-mismatching or not.

Methods

Eighty-one treated IA-Tx with the Solitaire stent retriever device, diagnosed as anterior circulation larger vessel occlusion were included in this study. Computed tomography-angiography (CTA) was done as an initial diagnostic image and acute stroke magnetic resonance image (MRI) followed after the IV-tPA. Forty-two patients were in the tPA group and 39 patients were in the non-tPA group. Recanalization rate, clinically significant hemorrhagic (sICH) and clinical outcomes were recorded according to the IV-tPA and P/D-mismatching.

Results

Recanalization rate was 81.0% in IV-tPA group, and it was 69.2% in non-tPA group (p = 0.017). While sICH were 19.9% and 25.6%, respectively (p = 0.328). Neurologic outcomes did not influence by IV-tPA administration or not. But according to the P/D-mismatching, the recanalization rate and sICH were 91.9% and 16.7% in the mismatched group and 46.7% and 46.7% in the matched group (p = 0.008 and p = 0.019, respectively).

Conclusion

For patients treated with IA-Tx with retrieval stent, IV-tPA infusion does not influence on the sICH, recanalization rate and neurologic outcomes. But P/D-mismatching was correlated well with sICH, recanalization rate and clinical outcomes.

The cerebral collateral circulation: Relevance to pathophysiology and treatment of stroke

The brain's collateral circulation consists of arterial anastomotic channels capable of providing nutrient perfusion to brain regions whose normal sources of flow have become compromised, as occurs in acute ischemic stroke. Modern CT-based neuroimaging is capable of providing detailed information as to collateral extent and sufficiency and is complemented by magnetic resonance-based methods. In the present era of standard-of-care IV thrombolysis for acute ischemic stroke, and following the recent therapeutic successes of randomized clinical trials of acute endovascular intervention, the sufficiency of the collateral circulation has been convincingly established as a key factor influencing the likelihood of successful reperfusion and favorable clinical outcome. This article reviews the features of the brain's collateral circulation; methods for its evaluation in the acute clinical setting; the relevance of collateral circulation to prognosis in acute ischemic stroke; the specific insights into the collateral circulation learned from recent trials of endovascular intervention; and the major influence of genetic factors. Finally, we emphasize the need to develop therapeutic approaches to augment collateral perfusion as an adjunctive strategy to be employed along with, or prior to, thrombolysis and endovascular interventions, and we highlight the possible potential of inhaled nitric oxide, albumin, and other approaches. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Expanding the concept of neuroprotection for acute ischemic stroke: The pivotal roles of reperfusion and the collateral circulation

This review surveys the efforts taken to achieve clinically efficacious protection of the ischemic brain and underscores the necessity of expanding our purview to include the essential role of cerebral perfusion and the collateral circulation. We consider the development of quantitative strategies to measure cerebral perfusion at the regional and local levels and the application of these methods to elucidate flow-related thresholds of ischemic viability and to characterize the ischemic penumbra. We stress that the modern concept of neuroprotection must consider perfusion, the necessary substrate upon which ischemic brain survival depends. We survey the major mechanistic approaches to neuroprotection and review clinical neuroprotection trials, focusing on those phase 3 multicenter clinical trials for acute ischemic stroke that have been completed or terminated. We review the evolution of thrombolytic therapies; consider the lessons learned from the initial, negative multicenter trials of endovascular therapy; and emphasize the highly successful positive trials that have finally established a clinical role for endovascular clot removal. As these studies point to the brain's collateral circulation as key to successful reperfusion, we next review the anatomy and pathophysiology of collateral perfusion as it relates to ischemic infarction, as well as the molecular and genetic influences on collateral development. We discuss the current MR and CT-based diagnostic methods for assessing the collateral circulation and the prognostic significance of collaterals in ischemic stroke, and we consider past and possible future therapeutic directions.

Clinical results of intraarterial thrombolysis according to tPA administration and perfusion/diffusion mismatching

BACKGROUND

IA-Tx and advanced dynamic imaging studies have been adopted for ischemic stroke patient treatment. Many patients are treated with IV-tPA, but this treatment is not always feasible. In this study, IA-Tx was used for patients for whom IV-tPA was not indicated or when IV-tPA did not result in recanalization.

METHODS

A total of 156 patients treated with IA-Tx were retrospectively reviewed. Of these, 72 patients were treated with a full dose of IV-tPA before receiving the IA-Tx; the remaining 84 patients only received IA-Tx. An initial imaging study using CTA and acute stroke MRI followed. Patients' demographics and clinical results were recorded and compared according to P/D mismatching and IV-tPA.

RESULTS

Among P/D-mismatched patients, the recanalization rate was 80 % and the symptomatic intracranial hemorrhage rate was 14.5 %, while among P/D-matched patients, the rates were 63 % and 41.3 % respectively (p < 0.05). A favorable clinical outcome occurred in 49.1 % of P/D-mismatched, but only in 21.7 % of P/D-matched patients (p < 0.05). Among patients who were treated with IV-tPA before undergoing IA-Tx, the recanalization rate was 79.2 % and the sICH rate was 27.8 %, while it was 71.4 % and 17.9 % in patients who did not receive IV-tPA (p < 0.05).

CONCLUSIONS

Patients who have P/D mismatching and are treated with IA-Tx have higher recanalization rates and a greater probability of a favorable outcome than patients who have P/D matching and receive IA-Tx. For patients who do not undergo successful recanalization after IV-tPA or who are not indicated for IV-tPA, the authors recommend IA-Tx after undergoing appropriate imaging evaluation.

Reperfusion therapies of acute ischemic stroke: potentials and failures

Over the past 20 years, clinical research has focused on the development of reperfusion therapies for acute ischemic stroke (AIS), which include the use of systemic intravenous thrombolytics (alteplase, desmoteplase, or tenecteplase), the augmentation of systemic intravenous recanalization with ultrasound, the bridging of intravenous with intra-arterial thrombolysis, the use of multi-modal approaches to reperfusion including thrombectomy and thromboaspiration with different available retrievers. Clinical trials testing these acute reperfusion therapies provided novel insight regarding the comparative safety and efficacy, but also raised new questions and further uncertainty on the field. Intravenous alteplase (tPA) remains the fastest and easiest way to initiate acute stroke reperfusion treatment, and should continue to be the first-line treatment for patients with AIS within 4.5 h from onset. The use of tenecteplase instead of tPA and the augmentation of systemic thrombolysis with ultrasound are both novel therapeutical modalities that may emerge as significant options in AIS treatment. Endovascular treatments for AIS are rapidly evolving due to technological advances in catheter-based interventions and are currently emphasizing speed in order to result in timely restoration of perfusion of still-salvageable, infarcted brain tissue, since delayed recanalization of proximal intracranial occlusions has not been associated with improved clinical outcomes. Comprehensive imaging protocols in AIS may enable better patient selection for endovascular interventions and for testing multi-modal combinatory strategies.

Adaptive choice of patient subgroup for comparing two treatments

This paper is motivated by a randomized controlled trial to compare an endovascular procedure with conventional medical treatment for stroke patients, in which the endovascular procedure may be effective only in a subgroup of patients. Since the subgroup is not known at the design stage but can be learned statistically from the data collected during the course of the trial, we develop a novel group sequential design that incorporates adaptive choice of the patient subgroup among several possibilities which include the entire patient population as a choice. We define the type I and type II errors of a test in this design and show how a prescribed type I error can be maintained by using the closed testing principle in multiple testing. We also show how asymptotically optimal tests can be constructed by using generalized likelihood ratio statistics for parametric problems and analogous standardized or Studentized statistics for nonparametric tests such as Wilcoxon's rank sum test commonly used for treatment comparison in stroke patients.