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Thomas R Fleming

Publications and source records attributed to Thomas R Fleming.

15 recordsLinked to original sources
PubMed2026

Select Contemporary Statistical Concepts in Heart Failure Clinical Trials: Insights From the Heart Failure Collaboratory.

Evolving statistical concepts and innovative trial designs for heart failure (HF) clinical trials seek to improve the conduct, efficiency, and likelihood of meaningful evidence generation crucial for advancing therapeutic development and optimizing patient care. HF trials with conventional statistical frameworks often require large sample sizes, long follow-up times, and high cost to generate sufficient evidence. Novel statistical methodologies would be of interest if they could address these issues while retaining or enhancing the clinical relevance and reliability of results. The HFC (Heart Failure Collaboratory), comprising clinical investigators, clinicians, statisticians, patients, government representatives, payors, and industry collaborators, leads efforts to improve HF research methodologies. HFC discussions have included statistical concepts such as the estimand framework, HR drift, and analytic methods, including the win ratio and restricted mean survival time, that have not been used frequently in HF trials. The estimand framework encourages precise definition and alignment of trial objectives with trial design. The win ratio method attempts to incorporate and prioritize multiple clinically meaningful outcomes by using a hierarchy of clinical importance. The restricted mean survival time provides an alternative to the HR as a measure of therapeutic effect by quantifying the mean time gained or lost during a fixed time after randomization. This paper provides a critical review of some evolving HF trial design methodologies and statistical concepts for the HF community as discussed within the HFC. Our goal is to foster collaboration among diverse stakeholders and advance the development of effective treatments and improve patient care outcomes.

Heart Failure↗
PubMed2006

A phase 2/3 multicenter randomized clinical trial of ABX-CBL versus ATG as secondary therapy for steroid-resistant acute graft-versus-host disease.

Treatment for steroid-resistant acute graft-versus-host disease (GVHD) has had limited success. ABX-CBL is a hybridoma-generated murine IgM monoclonal antibody against the CD147 antigen, weakly expressed on human leukocytes and up-regulated on activated lymphocytes. A prospective, multicenter, open-label, randomized clinical trial comparing ABX-CBL to antithymocyte globulin (ATG) for treatment of steroid-resistant acute GVHD was conducted in 95 patients at 21 centers. Forty-eight patients received ABX-CBL daily for 14 consecutive days followed by up to 6 weeks of ABX-CBL twice weekly. Forty-seven patients received equine ATG, 30 mg/kg every other day for a total of 6 doses with additional courses as needed. By day 180, overall improvement was similar in the patients receiving ABX-CBL and in those receiving ATG (56% versus 57%, P = .91). Patient survival at 18 months was less favorable on ABX-CBL than on ATG (35% versus 45%), with the 95% confidence interval ruling out that ABX-CBL provides at least a 10.4% improvement. Data from this trial suggest that ABX-CBL does not offer an improvement over ATG in the treatment of acute steroid-resistant GVHD. This prospective, multicenter, randomized clinical trial for steroid-resistant acute GVHD serves as a model for future evaluation of new agents.

Adolescent↗
PubMed2006

Standard versus adaptive monitoring procedures: A commentary.

In the standard approach to designing definitive clinical trials, the primary endpoint and test statistic to be used for the primary analysis are specified before trial initiation. The false positive error rate for the null hypothesis and statistical power to detect the targeted size of treatment effect are also specified. Standard monitoring procedures, such as the group sequential guidelines, enable interim monitoring while maintaining the integrity of this approach. In contrast, adaptive monitoring procedures seek to provide flexibility to modify these pre-specified design features during the course of the trial. However, these procedures have several undesirable properties, including lesser statistical efficiency, reduced interpretability of primary outcome results, basing design changes on unreliable interim estimates of efficacy, risks to the integrity and credibility of the trial, loss of flexibility to use emerging results from external sources to alter key design features, and overemphasis of the importance of statistical significance relative to clinical significance.

Clinical Trials Data Monitoring Committees↗
PubMed2006

Simultaneous use of weighted logrank and standardized Kaplan-Meier statistics.

Rank-based test procedures in censored survival data differ considerably in their sensitivity to various alternatives to the hypothesis of equality of underlying distributions. Procedures based on the simultaneous use of multiple statistics provide an appealing approach to obtaining more global sensitivity while maintaining the sensitivity to alternatives of interest. In this article, the joint distribution of weighted logrank statistics (to assess overall differences in time-to-event distributions) and a standardized difference in Kaplan-Meier estimates (to assess differences at a specific prespecified time post randomization) is obtained and this result is used to formulate statistical test procedures based on the simultaneous use of these two types of statistics. Simulations are used to assess small sample properties of this approach and its usefulness is illustrated in important recent oncology clinical trials.

Clinical Trials, Phase III as Topic↗
PubMed2005

A randomized double-blind trial of iseganan in prevention of ventilator-associated pneumonia.

RATIONALE: Iseganan, an antimicrobial peptide, is active against aerobic and anaerobic gram-positive and gram-negative bacteria as well as fungi and yeasts. The drug has shown little resistance in vitro and to be safe and well tolerated in 800 patients with cancer treated for up to 6 wk. OBJECTIVES: To determine the efficacy of iseganan for the prevention of ventilator-associated pneumonia (VAP). METHODS: Mechanically ventilated patients in the United States and Europe were randomized to oral topical iseganan or placebo (1:1) and treated six times per day while intubated for up to 14 d. Patients were eligible if randomized within 24 h of intubation and estimated to survive and remain mechanically ventilated for 48 h or more. The primary efficacy endpoint of the study was VAP measured among survivors at Day 14. MEASUREMENTS AND MAIN RESULTS: A total of 709 patients were randomized and received at least one dose of study drug. The two groups were comparable at baseline except iseganan-treated patients were, on average, 3 yr older. The rate of VAP among survivors at Day 14 was 16% (45/282) in patients treated with iseganan and 20% (57/284) in those treated with placebo (p = 0.145). Mortality at Day 14 was 22.1% (80/362) in the iseganan group compared with 18.2% (63/347) in the placebo group (p = 0.206). No pattern of excess adverse events in the iseganan group compared with placebo was observed. CONCLUSIONS: Iseganan is not effective in improving outcome in patients on prolonged mechanical ventilation.

Administration, Oral↗
PubMed2004

Some design issues in trials of microbicides for the prevention of HIV infection.

Trials for the prevention of human immunodeficiency virus (HIV) infection that evaluate microbicides provide significant design challenges. Three of these design issues deserve more careful consideration. The first issue relates to the benefits of using both blinded and unblinded control groups when the placebo regimen may not be inert and when the effectiveness of an intervention heavily depends on behavioral, as well as biological, factors. The second issue relates to the strength of evidence required for regulatory approval for the marketing of drugs and biologics when only a single pivotal phase 3 clinical trial has provided such evidence. The third issue relates to the appropriate next step after the completion of phase 1 trials, as well as the specific merits of conducting phase 2b screening trials that assess the effects on the same clinical efficacy end point that will be the primary end point in a phase 3 trial. The issues considered in microbicide trials for the prevention of HIV infection are also of importance in many other clinical scenarios.

Anti-HIV Agents↗
PubMed2004

The independent statistician for data monitoring committees.

Clinical trials are an essential part of the clinical research process. Recently, independent Data Monitoring Committees (DMCs) have been widely implemented to provide scientific and ethical oversight of pivotal clinical trials having irreversible outcomes such as death, stroke, disease recurrence or a serious adverse event. To carry out their responsibility, the DMC reviews interim analyses of accumulating data. We address the motivation for having the preparation and presentation of these interim analyses be conducted by an independent statistician who is not a member of the DMC and who is not the trial's lead or steering committee statistician. These views are based on having served as members of many DMCs as well as having been the independent statistician for several trials.

Bias↗
PubMed2004

Tolerance and safety of different concentrations of chlorhexidine for peripartum vaginal and infant washes: HIVNET 025.

BACKGROUND: There is a continuing need to evaluate sustainable interventions for prevention of mother-to-child transmission (MTCT) of HIV type 1. We evaluated different concentrations (0.25%, 1%, and 2%) of chlorhexidine (CHX) for perinatal maternal and infant washes to identify the maximum tolerable concentration of CHX for such an intervention. METHODS: Women were enrolled during their third trimester at the maternity unit of the Chris Hani Baragwanath Hospital in Soweto, South Africa, and perinatal maternal and infant washes were completed. Subjective maternal symptoms as well as infant examinations were used to assess tolerability of the washes. RESULTS: The 0.25% concentration of CHX was well tolerated by the mothers (n = 29). Ten of 79 women (13%) with 1% CHX washes complained of mild vaginal area burning or itching, and washes were stopped in 5 (6%). Twenty-three of 75 women (31%) in the 2% CHX wash group had subjective complaints, and the washes were stopped in 12 (16%). There were no clinical indications of toxicity of the CHX washes among infants. CONCLUSION: A 1% solution of CHX appears to be a safe and tolerable concentration of CHX for consideration in an MTCT prevention trial.

Acquired Immunodeficiency Syndrome↗
PubMed2004

A phase III, randomized, double-blind, placebo-controlled, study of iseganan for the reduction of stomatitis in patients receiving stomatotoxic chemotherapy.

The invasion and colonization of oral cavity mucosal tissues by microflora may contribute to the pathophysiology of ulcerative oral mucositis (UOM). Iseganan is an analog of protegrin-1, a naturally occurring peptide with broad-spectrum microbicidal activity. A randomized, double-blind, placebo-controlled study was conducted to evaluate the efficacy and safety of iseganan in preventing UOM after stomatotoxic therapy. Patients received an oral rinse, consisting of iseganan 9mg or placebo, to be swished/swallowed six times daily, starting with stomatotoxic therapy and continuing up to 21 days. Patients were assessed for stomatitis and UOM, and administered a questionnaire evaluating mouth pain and difficulty swallowing thrice weekly. The primary study efficacy endpoint was the proportion of patients who did not have peak stomatitis NCI-CTC grade >or=2. Between November 2001 and June 2002, 502 patients were randomized to receive iseganan (251) or placebo (251). Equivalent numbers of patients in both cohorts received bone marrow or peripheral blood allogeneic or autologous stem cell transplantation (SCT). Forty-three percent and 37% of iseganan and placebo patients, respectively, did not have peak stomatitis grade =2 (P = 0.182). There was no significant difference between the cohorts in stomatitis severity, incidence of UOM, peak mouth pain, peak difficulty swallowing, amount of opiate analgesics used, or adverse event type or incidence. A major impact of Iseganan on reducing stomatitis, UOM, or its clinical sequelae in patients receiving stomatotoxic therapy was not detected on this study.

Antimicrobial Cationic Peptides↗
PubMed2004

Liability issues for data monitoring committee members.

In randomized clinical trials, a data monitoring committee (DMC) is often appointed to review interim data to determine whether there is early convincing evidence of intervention benefit, lack of benefit or harm to study participants. Because DMCs bear serious responsibility for participant safety, their members may be legally liable for their actions. Despite more than three decades of experiences with DMCs, the issues of liability and indemnification have yet to receive appropriate attention from either government or industry sponsors. In industry-sponsored trials, DMC members are usually asked to sign an agreement delineating their responsibilities and operating procedures. While these agreements may include language on indemnification, such language sometimes protects only the sponsor rather than the DMC members. In government-sponsored trials, there has been even less structure, since typically there are no signed agreements regarding DMC activities. This paper discusses these issues and suggests sample language for indemnification agreements to protect DMC members. This type of language should be included in DMC charters and in all consulting agreements signed by DMC members.

Clinical Trials Data Monitoring Committees↗
PubMed2003

Adaptive test for testing the difference in survival distributions.

An adaptive test is proposed for the problem of testing the difference in survival distributions when the shape of the hazard ratio is unknown, hence the efficient test is unknown. The proposed adaptive test selects a test statistic from a finite set of the weighted logrank statistics T on the basis of the estimates of the efficiencies of the tests in T for given data. The efficiency estimator uses the length of the test based nonparametric confidence interval for the shift in a time transformed shift model. The suggested adaptive test is shown to be asymptotically efficient among the tests in T under the time transformed shift model and conditions commonly used in survival analysis. Simulations demonstrate that the adaptive test enjoys good small sample properties and in most situations is more powerful than the test using the maximum of the tests in T.

Computer Simulation↗
PubMed2003

A phase III, randomized, double-blind, placebo-controlled, multinational trial of iseganan for the prevention of oral mucositis in patients receiving stomatotoxic chemotherapy (PROMPT-CT trial).

Microfloral invasion and colonization of oral cavity mucosal tissues contribute to the pathophysiology of ulcerative oral mucositis (UOM). Iseganan is an analog of Protegrin-1, a naturally occurring peptide with broad-spectrum microbicidal activity. A randomized, double-blind, placebo-controlled study was conducted to evaluate iseganan in preventing UOM after stomatotoxic therapy. Patients received an oral rinse of iseganan 9 mg or placebo, swished/swallowed 6 times daily, starting with stomatotoxic therapy and continuing for 21-28 days. One hundred sixty three and 160 patients, respectively, were randomized to receive iseganan or placebo. One hundred and two patients (32%) were affected by a drug dispensing error, caused by a flawed computerized allocation system. Among all 323 patients, analyzed according to randomization assignment, 43% and 33% of iseganan and placebo patients, respectively, did not develop UOM (P = 0.067). On an 11-point scale, iseganan patients experienced less mouth pain (3.0 and 3.8 (P = 0.041), throat pain (3.8 and 4.6 (P = 0.048)), and difficulty swallowing (3.9 and 4.7 (P = 0.074)), compared to placebo patients. On the 5-point NCI CTC scale, iseganan patients experienced lower stomatitis scores (1.6 and 2.0 (P = 0.0131). Iseganan was well tolerated; no systemic absorption was detected. Iseganan is safe and may be effective in reducing UOM and its clinical sequelae.

Adolescent↗
PubMed2002

Monitoring clinical trials: issues and controversies regarding confidentiality.

During phase III clinical trials in life-threatening disease settings, it is important to ensure that the Data Monitoring Committee (DMC) has exclusive access to the interim efficacy and safety data generated by the data analysis centre, in order to minimize the risk of widespread prejudgement of unreliable trial results based on limited data. This prejudgement could adversely impact rates of patient accrual, continued adherence to trial regimens and ability to obtain unbiased and complete assessment of trial outcome measures. This also could result in publications of early results that might be very inconsistent with final study data on the benefit-to-risk profile of the study interventions. Circumstances arise only rarely in which unblinding of interim data beyond the DMC would enhance the ability of the trial to provide reliable results. However, to address the ethical imperative to protect the interests of study participants, the DMC itself should have access to unblinded efficacy and safety results.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Surrogate endpoints and FDA's accelerated approval process.

There is interest in approaches allowing more rapid availability of new interventions, particularly for diseases providing risks of death or serious illness. The accelerated-approval regulatory process is intended to address this need by allowing marketing of interventions shown to have strong effects on measures of biological activity, if those measures are potential "surrogates" for true measures of tangible clinical benefit. To use surrogate endpoints and the accelerated-approval process, challenging issues must be addressed to avoid compromising what is truly in the best interest of public health: the reliable as well as timely evaluation of an intervention's safety and efficacy.

Biomarkers↗