  We identify three properties of the standard oncology phase I trial design or
3 + 3 design. We show that the standard design implicitly uses isotonic
regression to estimate a maximum tolerated dose. We next illustrate the
relationship between the standard design and a Bayesian design proposed by Ji
et al. (2007). A slight modification to this Bayesian design, under a
particular model specification, would assign treatments in a manner identical
to the standard design. We finally present calculations revealing the behavior
of the standard design in a worst case scenario and compare its behavior with
other 3 + 3-like designs.
