Meta-Analyses and Adaptive Group Sequential Designs in the Clinical Development Process

The clinical development process can be viewed as a succession of trials, possibly overlapping in calendar time. The design of each trial may be influenced by results from previous studies and other currently proceeding trials, as well as by external information. Results from all of these trials must be considered together in order to assess the efficacy and safety of the proposed new treatment. Meta-analysis techniques provide a formal way of combining the information. We examine how such methods can be used in combining results from: (1) a collection of separate studies, (2) a sequence of studies in an organized development program, and (3) stages within a single study using a (possibly adaptive) group sequential design. We present two examples. The first example concerns the combining of results from a Phase IIb trial using several dose levels or treatment arms with those of the Phase III trial comparing the treatment selected in Phase IIb against a control This enables a "seamless transition" from Phase IIb to Phase III. The second example examines the use of combination tests to analyze data from an adaptive group sequential trial.

Efficient group sequential designs when there are several effect sizes under consideration

We consider the construction of efficient group sequential designs where the goal is a low expected sample size not only at the null hypothesis and the alternative (taken to be the minimal clinically meaningful effect size), but also at more optimistic anticipated effect sizes. Pre-specified Type I error rate and power requirements can be achieved both by standard group sequential tests and by more recently proposed adaptive procedures. We investigate four nested classes of designs: (A) group sequential tests with equal group sizes and stopping boundaries determined by a monomial error spending function (the 'rho-family'); (B) as A but the initial group size is allowed to be different from the others; (C) group sequential tests with arbitrary group sizes and arbitrary boundaries, fixed in advance; (D) adaptive tests-as C but at each analysis, future group sizes and critical values are updated depending on the current value of the test statistic. By examining the performance of optimal procedures within each class, we conclude that class B provides simple and efficient designs with efficiency close to that of the more complex designs of classes C and D. We provide tables and figures illustrating the performances of optimal designs within each class and defining the optimal procedures of classes A and B.

Inequalities in access to knee joint replacements for people in need

OBJECTIVES

To quantify the effects of socioeconomic deprivation and rurality on evidence of need for total knee joint replacement and the use of health services, after adjusting for age and sex.

METHODS

A random stratified sample of 15 000 people aged > or =65 years taken from central age/sex registers for the geographical areas covered by the previous Sheffield and Wiltshire Health Authorities. A self completion validated questionnaire was then mailed directly to subjects to assess need for knee joint replacement surgery and whether general practice and hospital services were being used. Subjects were followed up for 18 months to evaluate access to surgery.

RESULTS

The response rate was 78% after three mailings. In those aged 65 years and over (with and without comorbidity), the proportion with no comorbid factors and in need of knee replacement was 5.1%; the rate of need among subjects without comorbidity was 7.9%. There were inequalities in health and access to health related to age, sex, geography, and deprivation but not rurality. People who were more deprived had greater need. Older and deprived people were less likely to access health services. Only 6.4% of eligible people received knee replacement surgery after 18 months of follow up.

CONCLUSIONS

There is an important unmet need in older people, with significant age, sex, geographical, and deprivation inequalities in levels of need and access to services. The use of waiting list numbers as a performance indicator is perverse for this procedure. There is urgent need to expand orthopaedic services and training.

Inequalities in accessing hip joint replacement for people in need

OBJECTIVES

To quantify the effects of rurality and socio-economic disadvantage on prior evidence of need for total hip joint replacement and use of health services after adjusting for age and gender.

DESIGN

Self-completion validated questionnaire mailed directly to subjects.

SETTINGS

Geographical areas covered by Wiltshire and Sheffield Health Authorities in England.

PARTICIPANTS

Random stratified sample of 15,000 aged 65 years and over taken from the central age-sex registers.

MAIN OUTCOME MEASURE

Prior need for hip joint replacement surgery and whether general practice and hospital services were being used as assessed by the questionnaire.

RESULTS

The response rate was 78% after three mailings. Prevalence of need for total hip replacement in the over 64s was 3.4% (95% confidence interval is 3.0% to 3.8%) and in those without co-morbidity 5.4% (95% confidence interval is 4.8% to 6.0%). There were inequalities demonstrated due to age, geography, and deprivation, but not rurality in accessing general practice and hospital services. People who were poor had more need. Older people in need were less likely to be accessing health services.

CONCLUSIONS

There is an important unmet need for hip joint replacement in older people with marked inequalities in levels of need and use of services. The use of numbers of people waiting as a performance indicator is perverse for this procedure. We have urgently to expand orthopaedic services and the training of orthopaedic surgeons in England.

An evaluation of the safety and efficacy of simultaneous bilateral total knee arthroplasty

This study directly compared the clinical and radiographic results and patient satisfaction of a group of simultaneous, bilateral total knee arthroplasties (92) with a year of surgery matched unilateral total knee arthroplasties (92). Death within 1 month of surgery occurred in 1 bilateral patient and no unilateral patients. Significant cardiorespiratory complications were recorded in 6 bilateral patients and 2 unilateral patients. Patients with pre-existing cardiorespiratory conditions were particularly at risk. Analysis revealed a 98% 7-year survivorship for unilateral procedures and 97% for bilateral. In this study, 95% of bilateral patients stated they would choose the same option again.

Mid-course sample size modification in clinical trials based on the observed treatment effect

It is not uncommon to set the sample size in a clinical trial to attain specified power at a value for the treatment effect deemed likely by the experimenters, even though a smaller treatment effect would still be clinically important. Recent papers have addressed the situation where such a study produces only weak evidence of a positive treatment effect at an interim stage and the organizers wish to modify the design in order to increase the power to detect a smaller treatment effect than originally expected. Raising the power at a small treatment effect usually leads to considerably higher power than was first specified at the original alternative. Several authors have proposed methods which are not based on sufficient statistics of the data after the adaptive redesign of the trial. We discuss these proposals and show in an example how the same objectives can be met while maintaining the sufficiency principle, as long as the eventuality that the treatment effect may be small is considered at the design stage. The group sequential designs we suggest are quite standard in many ways but unusual in that they place emphasis on reducing the expected sample size at a parameter value under which extremely high power is to be achieved. Comparisons of power and expected sample size show that our proposed methods can out-perform L. Fisher's 'variance spending' procedure. Although the flexibility to redesign an experiment in mid-course may be appealing, the cost in terms of the number of observations needed to correct an initial design may be substantial.

Tumour necrosis factor alpha stimulated rheumatoid synovial microvascular endothelial cells exhibit increased shear rate dependent leucocyte adhesion in vitro

OBJECTIVE

To investigate endothelial cell adhesion molecule expression and leucocyte adhesion to endothelial cells isolated from the microvasculature of rheumatoid arthritic synovial tissue (SMEC) in comparison with similar cells isolated from healthy subcutaneous adipose tissue (ADMEC) or from umbilical veins (HUVEC).

METHODS

Cultured endothelial cells were treated with tumour necrosis factor alpha (TNFalpha) for 2-24 hours before the assessment of cell surface E-selectin, vascular (VCAM-1) or intercellular cell adhesion molecule-I (ICAM-1) expression. Neutrophil and T lymphocyte adhesion to TNFalpha treated endothelial cells was assessed using static and shear dependent assay systems.

RESULTS

VCAM-1 expression by SMEC was significantly less sensitive to TNFalpha stimulation than HUVEC or ADMEC. E-selectin expression by SMEC appeared to be more sensitive to TNFalpha stimulation and maximal expression was about 30% greater in comparison with HUVEC or ADMEC. Sensitivity to TNFalpha induction and maximal ICAM-1 expression was similar in all three endothelial cell types. Static neutrophil adhesion to TNFalpha stimulated SMEC was significantly increased in comparison with HUVEC, however this phenomenon was dependent on the presence of neutralising antibodies to ICAM-1. At shear rates in excess of 2.4 dynes/cm(2) significantly more neutrophils and, predominantly CD45RO+, T lymphocytes adhered to TNFalpha stimulated SMEC than HUVEC.

CONCLUSION

Rheumatoid synovial endothelial cells differentially regulate E-selectin and VCAM-1. The increased ability of TNFalpha stimulated synovial endothelial cells to support leucocyte adhesion may help to explain the leucocyte, in particular CD45RO+ T-lymphocyte, recruitment observed in the rheumatoid synovium.

Estimating the sample size for a t-test using an internal pilot

If the sample size for a t-test is calculated on the basis of a prior estimate of the variance then the power of the test at the treatment difference of interest is not robust to misspecification of the variance. We propose a t-test for a two-treatment comparison based on Stein's two-stage test which involves the use of an internal pilot to estimate variance and thus the final sample size required. We evaluate our procedure's performance and show that it controls the type I and II error rates more closely than existing methods for the same problem. We also propose a rule for choosing the size of the internal pilot, and show that this is reasonable in terms of the efficiency of the procedure.

Symmetric tests and confidence intervals for survival probabilities and quantiles of censored survival data

We describe existing tests and introduce two new tests concerning the value of a survival function. These tests may be used to construct a confidence interval for the survival probability at a given time or for a quantile of the survival distribution. Simulation studies show that error rates can differ substantially from their nominal values, particularly at survival probabilities close to zero or one. We recommend our new constrained bootstrap test for its good overall performance.