Tables of the number of patients required in clinical trials using the logrank test

The logrank test is commonly used in the analysis of clinical trials in chronic diseases such as cancer. Existing tables for the number of patients required in such trials are based on the direct comparison of two proportions. This paper presents tables of numbers required in clinical trials using the logrank test and describes their use. The numbers required are considerably smaller than those in existing tables when the event-free proportions are small, but otherwise comparable.