Estimation of conditional power in the presence of auxiliary data

Conditional power (CP) is a commonly used tool to inform interim decision-making in clinical trials, but the conventional approach using only primary endpoint data to calculate CP may not perform well when the primary endpoint requires a long follow-up period, or the treatment effect size changes during the trial. Several methods have been proposed to use additional short term auxiliary data observed at the interim analysis to improve the CP estimation in these situations, however, they may rely on strong assumptions, have limited applications, or use ad hoc choices of information fraction. In this paper we propose a general framework where the true CP formula is first derived in the presence of auxiliary data, and CP estimation is obtained by substituting the unknown parameters with consistent estimators. We conducted extensive simulations to examine the performance of both proposed and conventional approaches using the true CP as the benchmark. As the proposed approach is based on the true underlying CP, the simulations confirmed its superiority over the conventional approach in terms of efficiency and accuracy, especially if observed auxiliary data reflect the change of treatment effect size. The simulations also indicate that the magnitude of improvement in CP estimation is associated with the correlation between auxiliary and primary endpoints and/or the magnitude of the effect size change during the trial.

Early Termination of Clinical Trials for Futility - Considerations for a Data and Safety Monitoring Board

Early Termination of Clinical Trials for FutilityClinical trials may be stopped for futility if there is little or no chance of demonstrating the hoped-for effect. Reasons include evidence of no treatment effect, substantial missing data that would unacceptably undermine trial conclusions, or event rates too low to support meaningful comparisons. This review examines issues faced by DSMBs in such settings.

Efficacy and Safety of Enteral Recombinant Human Insulin in Preterm Infants: A Randomized Clinical Trial

IMPORTANCE

Feeding intolerance is a common condition among preterm infants owing to immaturity of the gastrointestinal tract. Enteral insulin appears to promote intestinal maturation. The insulin concentration in human milk declines rapidly post partum and insulin is absent in formula; therefore, recombinant human (rh) insulin for enteral administration as a supplement to human milk and formula may reduce feeding intolerance in preterm infants.

OBJECTIVE

To assess the efficacy and safety of 2 different dosages of rh insulin as a supplement to both human milk and preterm formula.

DESIGN, SETTING, AND PARTICIPANTS

The FIT-04 multicenter, double-blind, placebo-controlled randomized clinical trial was conducted at 46 neonatal intensive care units throughout Europe, Israel, and the US. Preterm infants with a gestational age (GA) of 26 to 32 weeks and a birth weight of 500 g or more were enrolled between October 9, 2016, and April 25, 2018. Data were analyzed in January 2020.

INTERVENTIONS

Preterm infants were randomly assigned to receive low-dose rh insulin (400-μIU/mL milk), high-dose rh insulin (2000-μIU/mL milk), or placebo for 28 days.

MAIN OUTCOMES AND MEASURES

The primary outcome was time to achieve full enteral feeding (FEF) defined as an enteral intake of 150 mL/kg per day or more for 3 consecutive days.

RESULTS

The final intention-to-treat analysis included 303 preterm infants (low-dose group: median [IQR] GA, 29.1 [28.1-30.4] weeks; 65 boys [59%]; median [IQR] birth weight, 1200 [976-1425] g; high-dose group: median [IQR] GA, 29.0 [27.7-30.5] weeks; 52 boys [55%]; median [IQR] birth weight, 1250 [1020-1445] g; placebo group: median [IQR] GA, 28.8 [27.6-30.4] weeks; 54 boys [55%]; median [IQR] birth weight, 1208 [1021-1430] g). The data safety monitoring board advised to discontinue the study early based on interim futility analysis (including the first 225 randomized infants), as the conditional power did not reach the prespecified threshold of 35% for both rh-insulin dosages. The study continued while the data safety monitoring board analyzed and discussed the data. In the final intention-to-treat analysis, the median (IQR) time to achieve FEF was significantly reduced in 94 infants receiving low-dose rh insulin (10.0 [7.0-21.8] days; P = .03) and in 82 infants receiving high-dose rh insulin (10.0 [6.0-15.0] days; P = .001) compared with 85 infants receiving placebo (14.0 [8.0-28.0] days). Compared with placebo, the difference in median (95% CI) time to FEF was 4.0 (1.0-8.0) days for the low-dose group and 4.0 (1.0-7.0) days for the high-dose group. Weight gain rates did not differ significantly between groups. Necrotizing enterocolitis (Bell stage 2 or 3) occurred in 7 of 108 infants (6%) in the low-dose group, 4 of 88 infants (5%) in the high-dose group, and 10 of 97 infants (10%) in the placebo group. None of the infants developed serum insulin antibodies.

CONCLUSIONS AND RELEVANCE

Results of this randomized clinical trial revealed that enteral administration of 2 different rh-insulin dosages was safe and compared with placebo, significantly reduced time to FEF in preterm infants with a GA of 26 to 32 weeks. These findings support the use of rh insulin as a supplement to human milk and preterm formula.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02510560.

The Futility of Futility Analyses in Adjuvant Trials in Hormone Receptor Positive Breast Cancer

An interim analysis is commonly used in phase III superiority trials to compare treatment arms, with the goal of terminating exposure of patients to ineffective or unsafe drugs, or to identify highly effective therapies for earlier public disclosure. Traditionally, interim analyses have been designed to identify early evidence of extremely large benefit of the experimental approach, potentially leading to early dissemination of effective treatments. Increasingly, interim analysis has also involved analysis of futility which may lead to early termination of a trial that will not yield additional useful information This presents an important challenge in early-stage hormone receptor positive breast cancer, where recurrence often occurs late, with a steady annual event rate up to 20 years. Early analysis of events may miss late treatment effects that can be observed only with longer follow-up. We discuss approaches to futility analysis in adjuvant clinical trials in hormone receptor positive breast cancer, the role of the Data Safety Monitoring Committee in such analyses, considerations of the potential harms versus benefits of treatment, and the risks of continuing versus early stopping of a trial.

Estimation of conditional power for cluster-randomized trials with interval-censored endpoints

Cluster-randomized trials (CRTs) of infectious disease preventions often yield correlated, interval-censored data: dependencies may exist between observations from the same cluster, and event occurrence may be assessed only at intermittent study visits. This data structure must be accounted for when conducting interim monitoring and futility assessment for CRTs. In this article, we propose a flexible framework for conditional power estimation when outcomes are correlated and interval-censored. Under the assumption that the survival times follow a shared frailty model, we first characterize the correspondence between the marginal and cluster-conditional survival functions, and then use this relationship to semiparametrically estimate the cluster-specific survival distributions from the available interim data. We incorporate assumptions about changes to the event process over the remainder of the trial-as well as estimates of the dependency among observations in the same cluster-to extend these survival curves through the end of the study. Based on these projected survival functions, we generate correlated interval-censored observations, and then calculate the conditional power as the proportion of times (across multiple full-data generation steps) that the null hypothesis of no treatment effect is rejected. We evaluate the performance of the proposed method through extensive simulation studies, and illustrate its use on a large cluster-randomized HIV prevention trial.

Effect of Caspofungin vs Fluconazole Prophylaxis on Invasive Fungal Disease Among Children and Young Adults With Acute Myeloid Leukemia: A Randomized Clinical Trial

IMPORTANCE

Children, adolescents, and young adults with acute myeloid leukemia are at high risk of life-threatening invasive fungal disease with both yeasts and molds.

OBJECTIVE

To compare the efficacy of caspofungin vs fluconazole prophylaxis against proven or probable invasive fungal disease and invasive aspergillosis during neutropenia following acute myeloid leukemia chemotherapy.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter, randomized, open-label, clinical trial enrolled patients aged 3 months to 30 years with newly diagnosed de novo, relapsed, or secondary acute myeloid leukemia being treated at 115 US and Canadian institutions (April 2011-November 2016; last follow-up June 30, 2018).

INTERVENTIONS

Participants were randomly assigned during the first chemotherapy cycle to prophylaxis with caspofungin (n = 257) or fluconazole (n = 260). Prophylaxis was administered during the neutropenic period following each chemotherapy cycle.

MAIN OUTCOMES AND MEASURES

The primary outcome was proven or probable invasive fungal disease as adjudicated by blinded central review. Secondary outcomes were invasive aspergillosis, empirical antifungal therapy, and overall survival.

RESULTS

The second interim efficacy analysis and an unplanned futility analysis based on 394 patients appeared to have suggested futility, so the study was closed to accrual. Among the 517 participants who were randomized (median age, 9 years [range, 0-26 years]; 44% female), 508 (98%) completed the trial. The 23 proven or probable invasive fungal disease events (6 caspofungin vs 17 fluconazole) included 14 molds, 7 yeasts, and 2 fungi not further categorized. The 5-month cumulative incidence of proven or probable invasive fungal disease was 3.1% (95% CI, 1.3%-7.0%) in the caspofungin group vs 7.2% (95% CI, 4.4%-11.8%) in the fluconazole group (overall P = .03 by log-rank test) and for cumulative incidence of proven or probable invasive aspergillosis was 0.5% (95% CI, 0.1%-3.5%) with caspofungin vs 3.1% (95% CI, 1.4%-6.9%) with fluconazole (overall P = .046 by log-rank test). No statistically significant differences in empirical antifungal therapy (71.9% caspofungin vs 69.5% fluconazole, overall P = .78 by log-rank test) or 2-year overall survival (68.8% caspofungin vs 70.8% fluconazole, overall P = .66 by log-rank test) were observed. The most common toxicities were hypokalemia (22 caspofungin vs 13 fluconazole), respiratory failure (6 caspofungin vs 9 fluconazole), and elevated alanine transaminase (4 caspofungin vs 8 fluconazole).

CONCLUSIONS AND RELEVANCE

Among children, adolescents, and young adults with acute myeloid leukemia, prophylaxis with caspofungin compared with fluconazole resulted in significantly lower incidence of invasive fungal disease. The findings suggest that caspofungin may be considered for prophylaxis against invasive fungal disease, although study interpretation is limited by early termination due to an unplanned interim analysis that appeared to have suggested futility.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01307579.

EOLIA trial: the future of extracorporeal membrane oxygenation in acute respiratory distress syndrome therapy?

This was a prospective, multi-centre randomised controlled trial that involved centres in 16 countries. The trial was designed as a group sequential analysis with data analysed after randomisation of every 60 participants; stopping rules were predefined using the two triangle method. The trial could be stopped due to safety (due to excessive mortality in the ECMO arm), efficacy or futility (if unlikely to reach a definitive result). The trial was designed to have a power of 80% and alpha level of 5% to detect an absolute risk reduction of 20%. It was hypothesised that the mortality would be 60% in the conventional arm and 40% in the ECMO arm. Mortality at 60 days was the primary outcome measured.

In the EOLIA trial, early use of ECMO did not significantly improve mortality at 60 days in patients with severe ARDS, but when used as a rescue modality ECMO might help improve survivalhttp://bit.ly/2XOjwSE