Recruitment time problems

The Berkeley Program. The first heavy-ion therapy program was initiated at Berkeley, and 433 patients were treated between 1975 and 1992 [47]. The program was limited by the availability of the machine and its complexity (which resulted in many unscheduled down times), and, as a consequence, there was a patient recruitment problem. 

The problems, I think, at the graduate level are much, much different, in my opinion, than at the undergraduate level. At the graduate level, you do have a smaller pool. The small pool of minority students who are interested in graduate school and who are well prepared tend to get offers to go to graduate schools at Johns Hopkins, Harvard, Duke, and all the top places. We have a difficult time recruiting top minority graduate students. So, we have to try to build an environment that makes it more attractive to them. 

Even a type II trial cannot escape these difficulties if the disease is serious. Consider an indication where potential female subjects for a trial present more frequently than males. Here, recruitment will stop for females at the point at which half as many female patients have been recruited as would be Indicated for an independent analysis and at a point when males are still being recruited. It might be argued, therefore, that there is no problem since an independent analysis is inappropriate for females. But what about future recruitment of females Will women from this point on be allocated to the standard therapy only If one were to continue to recruit female patients to the trial, one could reach a conclusion much earlier than by insisting that from this time onwards only males should be recruited. Is one justified in instituting a policy which will withhold such a potentially early conclusion for female patients, especially since such a conclusion might in any case be of benefit to male patients also ... 

As Whitehead (1997) points out, this can even occur with fixed sample size studies of survival analysis. For example, consider a fixed sample size trial with a recruitment over one year. We may have determined to analyse the results once the last patient recruited has been followed up for one year. This means, though, that patients recruited earlier in the trial will have been followed up longer those recruited at the beginning will, in fact, have been followed up for two years. Often this extra information will also be included in the analysis, which thus reflects a mixture of follow-up times from one to two years. However, once this analysis is complete it will still be possible to obtain further data and in a year s time an analysis of patients with 2-3 years follow up could be carried out. I think it is fair to say, however, that it is more likely to be a problem which makes itself known in a sequential rather than a fixed trial framework. Nevertheless, it is a potential feature of all forecasting systems that they are hostages to the future further information which embarrasses us can always arise. 

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