Level of evidence for therapeutic drug monitoring of taxanes

Abstract

Taxanes are anticancer drugs on the market for more than 10 years that are thought to be interesting for therapeutic drug monitoring (TDM): high inter- and intra-patient variability, relationship between exposure and efficacy and especially toxicity. Nevertheless, the paclitaxel and docetaxel characteristics result in different conclusions for these two molecules with respect to their TDM. For paclitaxel, the nonlinear pharmacokinetics makes that the parameter which seems the more reliable to toxicity or outcome is the time during which the plasma concentration exceeds 0.05 μm. Concentration controlled studies using Bayesian adaptation showed that the TDM of paclitaxel is feasible in routine. However, this target needs to be prospectively validated with new weekly schedules of administration, leading to a balance between 'recommended' and 'potentially useful'. For docetaxel, the 3-weekly administration, which is the more effective scheme, is also the more toxic. However, neutropenia can be individually modeled and efficiently predicted without using plasma drug concentrations. The docetaxel TDM using this docetaxel-related neutropenia modeling however needs to be prospectively validated in routine. The level of evidence of TDM thus 'needs to be assessed'.