Cancer trails often have enrollment restricted to those newly diagnosed or those having a number of relapses, as regulatory approvals are often tied to the stage of the disease - newly diagnosed or relapsed. At the link below is an approximate calculator to assess relative proportions of patients at sites who might qualify for a trial (relapsed or diagnosed) and those stable and responding through an enrollment period who may not qualify or consent for a trial. The calculator uses median times to event at diagnosis and after relapse, uses the exponential distribution and hence the approximation depends on a stable prognosis for the disease over a medium time frame. Further, computations assume a uniform disease incidence rate over time.
https://resourcetepee.com/free-statistical-calculators/estimating-clinical-trial-enrollment-eligible-subsets-in-oncology/
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Shankar Srinivasan, PhD,
Partner, Resource Tepee, LLC
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