An interface model for dosage adjustment connects hematotoxicity to pharmacokinetics.

When modeling is required to describe pharmacokinetics and pharmacodynamics simultaneously, it is difficult to link time-concentration profiles and drug effects. When patients are under chemotherapy, despite the huge amount of blood monitoring numerations, there is a lack of exposure variables to describe hematotoxicity linked with the circulating drug blood levels. We developed an interface model that transforms circulating pharmacokinetic concentrations to adequate exposures, destined to be inputs of the pharmacodynamic process. The model is materialized by a nonlinear differential equation involving three parameters. The relevance of the interface model for dosage adjustment is illustrated by numerous simulations. In particular, the interface model is incorporated into a complex system including pharmacokinetics and neutropenia induced by docetaxel and by cisplatin. Emphasis is placed on the sensitivity of neutropenia with respect to the variations of the drug amount. This complex system including pharmacokinetic, interface, and pharmacodynamic hematotoxicity models is an interesting tool for analysis of hematotoxicity induced by anticancer agents. The model could be a new basis for further improvements aimed at incorporating new experimental features.

New adaptive method for phase I trials in oncology.

Assessment of the maximum tolerated dose for a small sample of patients is the objective of phase I trials in oncology. We propose a new adaptive approach performing differentiation of each type of toxicity and their grades, definition of the dose-limiting toxicity as a logical combination of toxicity events, modeling of the risk of toxic events as a function of the drug dose, and integration of individual covariates. An application study with retrospective data from a phase I Taxol pediatric trial revealed age as an influential covariate, allowing individualization of a patient's maximum tolerated dose. A simulation study illustrates the practice of sequential inclusion of patients, of constraints in the dose-finding process and of trial stopping rules. The approach presented here allows quick maximum tolerated dose assessment with a small sample of patients and assists the design of phase I trials in oncology.