RE: Down, But Not Out (1)13 Apr 2022 13:28
To pass futility you just have to show that you have a reasonable chance of meeting the trial's goals. You don't actually have to meet them.
http://onbiostatistics.blogspot.com/2012/03/futility-analysis-in-clinical-trials.html
"An example for futility analysis: at the beginning of the trial, we assumed 65% successful rate for new treatment group and 50% successful rate for the control group. We would like to establish superiority. In the middle of the study, we did an interim analysis. The interim analysis showed 55% successful rate for new treatment group and 50% successful rate for the control group. Based on the results from the interim analysis, we can calculate the probability and conditional power: if we continue to finish the study, what is the probability of the new treatment group better than control? If this probability is too small and meets the pre-specified criteria, we would stop the trial for futility. If this probability is reasonable, we can continue the trial as pre-planned"