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Group Sequential Designs and Sample Size Re-estimation

Cytel is conducting a webinar series that introduces biostatisticians to some of the more commonly used complex innovative trial designs. Our second webinar from this series was held on June 3, 2020, with Professor Christopher Jennison. Professor Jennison spoke about the modern uses of Group Sequential Designs and Sample Size Re-estimation. Group Sequential Designs were one of the earliest deviations from a traditional two-arm clinical trial with no interim looks at the data. They still add amazing value to trials through their abilities to safeguard patients, reach positive conclusions early and keep trial designs simple and streamlined. Sample Size Re-estimation is another key tool in the modern trial designer’s toolkit.

Cytel also did an interview with Professor Jennison where he spoke to us about these methods, their origin and how they add value to the industry. Continue reading this blog for a summary of the webinar. Click on the button below to access the webinar replay and download the presentation slides.

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For the purpose of this webinar, Professor Jennison focused on the design of Phase 3 trials. This phase is large and expensive, and more importantly, crucial in the process of drug approval. The challenge in a group sequential design is to reduce the length of these Phase 3 trials, thereby saving resources and reaching the conclusion sooner.

A fixed sample study is longer than a group sequential trial and does not involve any interim analysis. These pre-planned interim analyses in sequential designs enable early stopping when preliminary results clearly demonstrate efficacy or futility. Also, a group sequential design with two or three analyses and a small increase in sample over the fixed sample test can reduce expected sample size by around 30%.

Professor Jennison explains the theory behind group sequential method and how it works, through case studies. He uses an example of a trial for a cholesterol lowering drug and demonstrates how a fixed sample design and a group sequential design can be created on Cytel’s software East®. It is quite difficult to beat these designs in terms of getting a lower average sample size under various treatment effects.

Sample size re-estimation is another method to seek the same benefits of reduced sample size and an earlier conclusion. In a group sequential test, we set a large sample size and hope to stop early. The philosophy that underlines the idea of sample size re-estimation is that we turn things the other way around, we start with a small study and possibly increase the sample size post an interim analysis. We then analyze the final set of data and make a conclusion.

To get more insights on these methods and see a demonstration of examples on our East® software, access the webinar recording and download the presentations slides.

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Register for the remaining webinars in the Cytel “Introduction to Complex Innovative Trial Design” webinar series.



About Professor Christopher Jennison

christopher jennisonChristopher Jennison is Professor of Statistics at the University of Bath, UK. His PhD research at Cornell University concerned the sequential analysis of clinical trials and he has continued to work in this area for over 35 years. His book with Professor Bruce Turnbull, "Group Sequential Methods with Applications to Clinical Trials", is a standard text on this topic and is widely used by practicing statisticians. More recently, he has written with a variety of co-authors on adaptive trial design and over-arching optimization of the drug development process.

Professor Jennison's research is informed by experience of clinical trial analysis at the Dana Farber Cancer Institute, Boston and a broad range of consultancy with Pharmaceutical companies. 

Click here to learn more about Professor Jennison and access his publications.


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