Association of 5-FU Therapeutic Drug Monitoring to DPD Phenotype Assessment May Reduce 5-FU Under-Exposure.

In order to limit 5-fluorouracil (5-FU) toxicity, some health agencies recommend evaluating dihydropyrimidine dehydrogenase (DPD) deficiency before any 5-FU treatment introduction. In our study, we investigated relationships between 5-FU clearance and markers of DPD activity such as uracilemia (U), dihydrouracilemia (UH2)/U ratio, or genotype of the gene encoding DPD (DPYD). All patients with gastrointestinal cancers who received 5-FU-based regimens form March 2018 to June 2020 were included in our study. They routinely benefited of a pre-therapeutic DPYD genotyping and phenotyping. During 5-FU infusion, blood samples were collected to measure 5-FU steady-state concentration in order to adapt 5-FU doses at the following cycles. A total of 169 patients were included. Median age was 68 (40-88) years and main primary tumor sites were colorectal (40.8%) and pancreas (31.4%), metastatic in 76.3%. 5-FU was given as part of FOLFIRINOX (44.4%), simplified FOLFOX-6 (26.6%), or docetaxel/FOLFOX-4 (10.6%). Regarding DPD activity, median U and UH2/U were, respectively, 10.8 ng/mL and 10.1, and almost 15% harbored a heterozygous mutation. On the range of measured U and UH2/U, no correlation was observed with 5-FU clearance. Moreover, in patients with U < 16 ng/mL, 5-FU exposure was higher than in other patients, and most of them benefited of dose increase following 5-FU therapeutic drug monitoring (TDM). If recent guidelines recommend decreasing 5-FU dose in patients harboring U ≥ 16 ng/mL, our study highlights that those patients are at risk of under-exposure and that 5-FU TDM should be conducted in order to avoid loss of efficacy.

[Level of evidence for therapeutic drug monitoring of everolimus]. / Évaluation du niveau de preuve du suivi thérapeutique pharmacologique de l'évérolimus.

Everolimus has proven efficacy for prevention of rejection in adult de novo renal and cardiac transplant recipient in combination with ciclosporine and corticosteroids. Therapeutic drug monitoring (TDM) with target trough concentration (C0) value from 3 to 8 µg/L has been proposed. Through a systematic review of the literature, this work explored a level of recommendation for this TDM. Everolimus exhibits both wide interindividual pharmacokinetic variability and poor relationship between dose and exposure. A good relationship has been reported between C0 values and global exposure to the drug (i.e. AUC). Although C0 > 3 µg/L has been associated with a decreased incidence of rejection, the upper limit of 8 µg/L has never been formally validated. No clinical trial testing other exposure indices or comparing efficacy and/or toxicity of everolimus therapy with and without TDM has been published so far. Consequently the level of recommendation for everolimus monitoring is "recommended".

Population pharmacokinetics and dosing recommendations for cisplatin during intraperitoneal peroperative administration: development of a limited sampling strategy for toxicity risk assessment.

BACKGROUND: Ovarian cancer is the leading cause of gynaecological cancer-related death in Western countries. Intraperitoneal (IP) peroperative chemotherapy is an interesting therapeutic option. However, very few data are available regarding pharmacokinetics and especially population pharmacokinetics. PATIENTS AND METHODS: Thirty-one patients with advanced epithelial cancer classified as International Federation of Gynecology and Obstetrics stage IIIC were included in the study. Blood and IP samples were taken over a 24-hour period during and after IP treatment. Both total and ultrafiltered (Uf) platinum (Pt) concentrations were analysed using a population approach with nonlinear mixed-effects modelling (NONMEM) software. Improvement of the model with covariates was performed as well as assessment of the model using bootstrap and posterior visual predictive methods. RESULTS: Both IP fluid and serum pharmacokinetics were satisfactorily described with a three-compartment model for both Uf Pt and total Pt concentrations. The covariates were bodyweight for the IP volume of distribution in the Uf Pt model, and both IP and serum protein concentrations for the clearance from the central compartment in the total Pt model. A nomogram, based on the results of the Monte Carlo simulations, displays a dose recommendation regarding both the risk of renal toxicity and the potent efficacy of the treatment. A limited sampling strategy (LSS) allowing the estimation of potential risk of renal toxicity is also described. CONCLUSION: The pharmacokinetics of cisplatin during peroperative IP chemotherapy could be successfully fitted with the present model, which allowed a dosing strategy accompanied by an LSS to facilitate the follow-up of patients.