[To which criterion should the dosage of anticancer drug be adapted?]

The dose of anticancer drugs is currently adjusted to the body surface area of the patient, although for a given body surface, patients have different distribution and metabolism for a given drug. The dose adjustment to the tumour drug content was studied, we noted that it is not always possible to obtain a tumour sample; the sample and its drug content may not be representative of the whole tumour content, this measured drug content is neither indicative for the evaluation of the dose to be administered, nor indicative of the chemotherapy efficacy. The best criterion for the dose adjustment seems to be the plasma concentration of the drug. Correlations between drug plasma concentration and clinical data are examined. The relationship between plasma concentration and efficacy cannot be excellent, since it depends on the presence of resistant cells and on the blood flow through the tumour. A relationship between plasma concentration and toxicity has been reported with many anticancer drugs. The drug plasma concentration and the area under the curve (AUC) give better correlations than the administered dose with efficacy and toxicity. Different methods of dose adjustment are reported. They use mathematical models which allow to decrease the number of blood samples, without losing precision in the pharmacokinetic parameter evaluation. In conclusion, the dose adjustment to the drug plasma concentration or to the AUC can play an important role in improving the chemotherapy efficacy, while toxicity is reduced.