Population pharmacokinetic and pharmacodynamic analysis for time courses of docetaxel‐induced neutropenia in Japanese cancer patients

The present study describes a population pharmacokinetic and pharmacodynamic (PK/PD) analysis based on data obtained from cancer patients treated with docetaxel at the National Cancer Center Hospital East in Japan. Docetaxel was infused intravenously over 1 h every 3 weeks, and time courses of absolute neutrophil counts (ANC) for a total of 395 observations (62 patients) were analyzed using a semimechanistic‐physiological PK/PD model in the NONMEM program. The prominent feature of our PK/PD model is that it has the capability to predict a temporary increase in ANC. Among 10 patient factors, α1‐acid glycoprotein was selected as a significant covariate for drug effect as the increase in α1‐acid glycoprotein was negatively correlated with the drug effect. Goodness‐of‐fit plots indicated that the model fitted well with the observed data, and the bootstrap method guaranteed robustness of the model. In conclusion, we developed a novel population PK/PD model that can adequately analyze ANC profiles after docetaxel administration in oncology practice, where temporary but consistent increases in ANC were observed. (Cancer Sci 2007; 98: 1985–1992)