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There is a time frame involving them and you can believe, where on that time frame does the surrogate lie? It might be near the true endpoint--for instance, if overall survival could be the real endpoint, then a thing occurring close to the time of death would be a possible surrogate. An example in the other end of your scale: you might have a therapy which is trying to adjust the immune method. Then, a potential surrogate could possibly be some measure with the immune method, which you will have soon just after commence of therapy. This will be at the other end of the timescale. It really is probably going to be tougher to locate excellent surrogates extremely close to the time of therapy that happen to be going to generalize to other trials. Which is for the reason that the decision of surrogate would ordinarily be rather specific to the therapy, plus the causal connection between the surrogate and also the true outcome might not be strong. But the causal connection between near death and death is likely going to be preserved. So, my opinion is the fact that we're far more probably to have achievement in establishing surrogates which can be closer to the true endpoint.Clin Trials. Author manuscript; accessible in PMC 2015 November 22.Daniels et al.PageDr Ghosh produced a comment regarding the level of information that is needed, and that if you have information in the complete trial anyway what exactly is the point in wanting to establish the usefulness of a surrogate. He was speaking in regards to the treatment effects on the correct endpoint at time T1 offered the effect around the surrogate at time T0. One question is, are you able to shorten the trial? To complete the estimation you will need excellent follow-up data on a lot of people, not necessarily everybody. For anyone who is going to analyze information from a trial, people today enroll more than a time span of 4 years, say, after which there is a certain volume of follow-up. The first enrollee features a extended data history plus the last enrollee features a brief data history, so you have some facts out to the longest follow-up time. You don't necessarily want everyone to possess complete follow-up. You could potentially extrapolate for a person out to that range where you have got some information on other folks and nonetheless remain inside the bounds of your data, conditional around the models that you are specifying. There was a comment about randomized phase II trials in oncology and that their final results haven't been that effective at predicting what exactly is going to operate in phase III trials. I believe the point was if we could have each of the information from those randomized trials maybe we could analyze it and understand about the causal relationships inside these trials, and with that original raw data accessible, 1 could make improved options about what could possibly function in phase III, as an alternative to just relying on significance tests from usually also small phase II trials. Phase II trials in oncology ordinarily aren't significant sufficient to get a lot confirmatory evidence. Instead of only taking a look at irrespective of whether a significance level is attained or not in a phase II study and assessing whether or not that predicts the phase III result, it may be valuable to endeavor to discover from the data about the causal mechanisms that may be additional informative about no matter whether to go on to phase III.Author Manuscript Author Manuscript Author Manuscript Author ManuscriptSongbai WangTraditionally, I think a lot of people make use of the Prentice criteria to evaluate a biomarker to see if which will be classified as a surrogate endpoint an.