Practical Considerations in Sample Size Determination of Japanese Subgroup for a Multi-Regional Oncology Clinical Trial

For Japanese pharmaceutical companies, one of the critical issues in the design of multi-regional clinical trials (MRCT) is the number of Japanese patients. In the document issued by the Ministry of Health, Labour and Welfare (MHLW) in 2007, “Basic principles on Global Clinical Trials,” an issue was raised about the Japanese subgroup sample size and the importance of “consistency of results.” Ideas on how to calculate the sample size of a given region and the regions overall have been proposed by Uesaka (2006, 2009). For this purpose, he identified two types of consistency criteria and two types of efficacy criteria. For both efficacy and consistency these types consist of either 1) comparing the results of a specific region with those of the other regions combined, or 2) comparing the results of a specific region with those of the regions overall. Based on the efficacy criterion 2, Sekiguchi et al. (2007) examined the sample size of the Japanese subgroup in an oncology MRCT.In this study, we present a simulation that shows the relationship of Japanese subgroup sample size to both types of efficacy criteria in an oncology MRCT.