An extension of the single threshold design for monitoring efficacy and safety in phase II clinical trials.

Tan and Machin (biStat. Med. 2002; 21:1991-2012) introduce a Bayesian two-stage design for phase II clinical trials where the binary endpoint of interest is treatment efficacy. In this paper we propose an extension of their design to incorporate safety considerations. At each stage we define the treatment successful and deserving of further study if the total number of adverse events is sufficiently small and the number of responders who simultaneously do not experience any toxicity is sufficiently large. Therefore, our criterion is based on the joint posterior probability that the true overall toxicity rate and the true efficacy-and-safety rate are, respectively, smaller and larger than conveniently pre-specified target values. The optimal two-stage sample sizes are determined specifying a minimum threshold for the above-mentioned posterior probability, computed under the assumption that favorable outcomes have occurred. Besides describing the proposed design, we suggest how to construct informative prior scenarios and we also apply the reference algorithm to derive a non-informative prior distribution. Finally, some numerical results are provided and a real data application is illustrated.

Can we eliminate placebo in ALS clinical Trials?

Amyotrophic lateral sclerosis (ALS) is a fatal disease with limited treatment options. Controlled studies are a necessary part of Phase II and Phase III assessments of proposed therapies. Due to the relatively small number of patients with ALS, several study designs have been proposed to improve the efficiency of Phase II studies. Some of these advocate the use of historical controls in place of placebo controls. However, the characteristics of historical controls may not mirror those of patients in the treatment group. Novel study designs can be used to decrease the number of patients required for Phase II studies. The use of placebo controls rather than historical controls in these novel study designs likely leads to better predictions of treatments that will be successful in Phase III studies. There is general agreement on the necessity of placebo controls in Phase III studies.

A computationally simple bivariate survival estimator for efficacy and safety.

Both treatment efficacy and safety are typically the primary endpoints in Phase II, and even in some Phase III, clinical trials. Efficacy is frequently measured by time to response, death, or some other milestone event and thus is a continuous, possibly censored, outcome. Safety, however, is frequently measured on a discrete scale; in Eastern Cooperative Oncology Group clinical trial E2290, it was measured as the number of weekly rounds of chemotherapy that were tolerable to colorectal cancer patients. For the joint analysis of efficacy and safety, we propose a non-parametric, computationally simple estimator for the bivariate survival function when one time-to-event is continuous, one is discrete, and both are subject to right-censoring. The bivariate censoring times may depend on each other, but they are assumed to be independent of both event times. We derive a closed-form covariance estimator for the survivor function which allows for inference to be based on any of several possible statistics of interest. In addition, we derive its covariance with respect to calendar time of analysis, allowing for its use in sequential studies.

Monitoring participant safety in phase I and II interventional trials: options and controversies.

BACKGROUND: The need for phase I and II clinical trials to have a data and safety monitoring plan (DSMP) is widely accepted; however, whether and/or when these trials should also have oversight by a data and safety monitoring board (DSMB) is controversial. Monitoring requirements also depend on whether the study is funded by the National Institutes of Health, funded and/or monitored by the US Food and Drug Administration (FDA), or funded by industry. However, there is little guidance about when and how to constitute a DSMB for phase I and II clinical trials. OBJECTIVES: The objectives of this article are to suggest guidelines for when and how to constitute a DSMB for phase I and II studies and to highlight the similarities and differences between DSMBs monitoring phase I and II versus phase III clinical studies. We highlight the utility of these guidelines in the safety monitoring of a mechanism of disease-based study of inhaled nitric oxide for acute vaso-occlusive crisis in pediatric patients with sickle cell disease that was funded and regulated by the FDA. CONCLUSION: The goal of DSMPs regardless of the phase of the clinical trial is to protect participant safety and ensure the integrity and validity of the data. A DSMB can ensure that risks and data are evaluated in a timely, efficient, and unbiased manner. We describe "risk-based" guidelines to determine situations in which a DSMB may be an appropriate addition to a DSMP for phase I and II clinical trials. We also address the roles and responsibilities of the DSMB for these studies.

Optimal continuous sequential boundaries for monitoring toxicity in clinical trials: a restricted search algorithm.

Continuous monitoring of severe adverse experiences can ensure the timely termination of a clinical trial if the therapy is shown to be harmful. In this paper we present methods for choosing a stopping rule for continuous monitoring of toxicity in small trials. They are especially useful for small phase II trials of about 30 patients for monitoring a binary toxicity event that is observed relatively quickly compared to the efficacy outcome. In 1987 Goldman described an algorithm for computing the exact type I error rate (alpha) and power (1-beta) of a specified discrete stopping boundary for sequential monitoring of a study with a fixed maximum number of patients (N) to be enrolled on the experimental therapy. Only an upper boundary was used since trials are only terminated for an excess frequency of toxicity and not for a low rate. By repeated use of this algorithm a stopping rule can be identified which has nearly the chosen level of (alpha) and a reasonable power depending on the design parameters of the study. The work reported here embeds this earlier algorithm as a subroutine in a larger FORTRAN program which searches all boundaries that fulfil constraints on size and power, as specified by the user. The search is restricted so that only those boundaries with size in a small neighbourhood of the chosen alpha are examined and displayed if the power is above a set minimum. These restrictions reduce the number of boundaries examined to only 0.4 per cent of all possible boundaries, thus reducing running time to a practical few seconds. Many such boundaries exist, the one with the largest power can then be chosen for monitoring the trial. The average sample number (ASN) and the expected relative loss (ERL) are also computed. The criterion for choosing may also be based on small ASN or low ERL in addition to power and appropriate alpha.

Willingness to participate in HIV-1 vaccine efficacy trials and the effect of media events among gay and bisexual men in New York City: Project ACHIEVE.

Efficacy trials of candidate HIV-1 vaccines require study populations at high risk of infection who adhere to study protocols and who are willing to participate. Data from HIV-1 antibody-negative men (n = 698) enrolled in Project ACHIEVE in New York City were analyzed to assess willingness to participate in efficacy trials, factors influencing willingness, and the effect on willingness of the June 1994 media events about the decision not to proceed with phase III trials and about breakthrough infections during phase I and II vaccine trials. Sixty-eight percent indicated they would definitely or probably be willing to participate. Men enrolled during the time of media events were significantly less willing compared with men enrolled during other periods. These men were also more likely to mention safety of the vaccine, fear or mistrust of research or government, and social risks as important factors in their decision compared with men enrolled during other periods. The most frequently cited motivator for participation was altruism (57%); the most frequently cited barriers were vaccine safety (36%) and vaccine-induced seropositivity (19%). A substantial proportion of this cohort was willing to participate in future vaccine efficacy trials. However, because willingness may be affected by issues of vaccine safety, vaccine-induced seropositivity, and media coverage of these issues, significant efforts are needed for participant and community education, and specific concerns must be addressed in the design and implementation of trials.

Telephone-based nursing intervention improves the effectiveness of the informed consent process in cancer clinical trials.

PURPOSE: Here we report the results of a randomized study undertaken to test the efficacy of a supplementary, telephone-based nursing intervention in increasing patients' awareness and understanding of the clinical trials in which they are asked to participate. METHODS: During a 12-month period, 180 cancer patients who were approached to participate in a phase II or III clinical trial were randomized to undergo either of the following: (1) standard informed consent procedures based on verbal explanations from the treating physician plus written information (controls); or (2) standard informed consent procedures plus a supplementary, telephone-based contact with an oncology nurse (intervention). For purposes of evaluation, face-to-face interviews were conducted with all patients approximately 1 week after the informed consent process had been completed. RESULTS: The two groups were comparable with regard to sociodemographic and clinical variables. Both groups had a high level of awareness of the diagnosis and of the nature and objectives of the proposed treatments. The intervention group was significantly (P < .01) better informed about the following: (1) the risks and side effects of treatment; (2) the clinical trial context of the treatment; (3) the objectives of the clinical trial; (4) where relevant, the use of randomization in allocating treatment; (5) the availability of alternative treatments; (6) the voluntary nature of participation; and (7) the right to withdraw from the clinical trial. The intervention did not have any significant effect on patients' anxiety levels or on rates of clinical trial participation. Patients reported high levels of satisfaction with the intervention. CONCLUSION: The use of a supplementary, telephone-based nursing intervention is a feasible and effective means to increase cancer patients' awareness and understanding of the salient issues that surround the clinical trials in which they are asked to participate.