What Were They Thinking? Pharmacologic priors implicit in a choice of 3+3 dose-escalation design

If explicit, formal consideration of clinical pharmacology at all informs the design and conduct of modern oncology dose-finding trials, the designs themselves hardly attest to this. Yet in conducting a trial, investigators affirm that they hold reasonable expectations of participant safety - expectations that necessarily depend on beliefs about how certain pharmacologic parameters are distributed in the study population. Thus, these beliefs are implicit in a trial's presumed conformance to a community standard of safety, and may therefore to some extent be reverse-engineered from trial designs. For one popular form of dose-escalation trial design, I demonstrate here how this may be done.