ABSTRACT
It is sometimes the case in phase I dose-finding studies in cancer that there exist more than one treatment schedule. The doses of a single agent can be expressed in multiple ways based on how the treatment will be given and the frequency in which it is administered. For instance, whether a dose is given once a day for 3 days in a particular week or given once that week is likely to have an impact on the probability of observing dose-limiting toxicity (DLT) for that dose. Each of these “courses of therapy” can be considered a distinct combination of schedule and dose. For these trials, finding an acceptable dose and schedule becomes a two-dimensional dose-finding problem, where one dimension is the dose level of the agent and the other is the course of therapy. The goal becomes to find a dose–schedule combination with tolerable toxicity.
