[Continual reassessment method (CRM)]

We discuss the basic concept of the continual reassessment method (CRM) and some modifications. The CRM has been proposed as alternatives of traditional cohort design for phase I trials in cancer. To focus on the dilemma between ethical concern and scientific purpose, we review the requirement for the phase I settings and the issues of the traditional cohort design. Then, CRM is introduced so that the essential feature is in the sequential (continual) selection of a dose level for next patients based on the dose-toxicity relationship and in updating the relationship based on patients' response date using Bayesian calculation. Finally we discuss both advantages and pitfalls in practice.