Optimization of G-CSF dosing schedule in patients treated with eribulin: a modeling approach.

BACKGROUND: Granulocyte colony-stimulating factors (G-CSF) are commonly given to limit chemotherapy-induced neutropenia, but, in case of weekly chemotherapy such as eribulin, their administration schedules remain empirical. OBJECTIVES: This pharmacokinetic/pharmacodynamic (PK/PD) study was conducted to establish the effect of different G-CSF regimens on neutropenia's incidence for patients treated by eribulin, to propose an optimal G-CSF dosing schedule. METHODS: A population PK/PD model was developed to describe absolute neutrophil counts' (ANC) time course in 87 cancer patients receiving eribulin. The structural model considered ANC dynamics, neutropenic effect of eribulin and stimulating effect of G-CSF. Final model estimates were used to calculate neutropenia's incidence following different G-CSF dosing schedules for 1000 virtual subjects. RESULTS: The final model successfully described most of the ANC time course for all patients. Simulations showed that a single G-CSF administration 48 h after each eribulin injection reduced the risk of severe neutropenia from 29.7 to 5.2%. Five days of G-CSF only after the second eribulin injection or no G-CSF administration induces similar incidence of neutropenia. CONCLUSION: Simulations showed a single G-CSF administration 48 h after the end of each eribulin injection seems to be the optimal schedule to reduce eribulin-induced neutropenia. However, the new administration scheme should be tested in real life to evaluate its pertinence. TRIAL REGISTRATION: Eudract 2015-001753-32, 2015/01/26.

Population pharmacokinetic and pharmacodynamic modeling of capecitabine and its metabolites in breast cancer patients.

PURPOSE: The present study was performed to examine relationships between systemic exposure of capecitabine metabolites (5-FU, 5'-DFCR and 5'-DFUR) and toxicity or clinical response in patients with metastatic breast cancer. METHODS: A population pharmacokinetic model for capecitabine and its three metabolites was built. Typical parameter values, characteristics of random distributions, associated with parameters, and covariates impact were estimated. Area under the curve (AUC) were computed for 5-FU and compared with grades of toxicity. Pharmacokinetic modeling was based on data collected on the first treatment cycle. Toxicity was assessed on the two first treatment cycles. RESULTS: The study was conducted in 43 patients. The population pharmacokinetic model (a one-compartment model per compound) was able to capture the very complex absorption process of capecitabine. Statistically significant covariates were cytidine deaminase, alkaline phosphatase and dihydrouracilemia (UH2)/uracilemia (U) ratio. UH2/U ratio was the most significant covariate on 5-FU elimination and CDA on the transformation of 5'-DFCR in 5'-DFUR. A trend was observed between 5-FU AUC and thrombopenia toxicity grades, but not with other toxicities. Best clinical response was not linked to systemic exposure of capecitabine metabolites. CONCLUSION: In our study, we propose a model able to describe, meanwhile, and its main metabolites, with a complex absorption process and inclusion of enzyme activity covariates such as CDA and UH2/U ratio. Trial registration Eudract 2008-004136-20, 2008/11/26.

Lack of everolimus diffusion in pleural fluid during pleural progression of breast cancer: A case report.

BACKGROUND: We report here a case where no everolimus pleural diffusion was evidenced at the same time of pleural progression of a metastatic breast cancer treated with everolimus and exemestane. CASE DESCRIPTION: A 69-year-old woman was diagnosed in October 2006 with stage III invasive ductal breast adenocarcinoma. After nine months of everolimus and exemestane treatment, she presented with a pleural progression. Everolimus concentration was measured in blood and in pleural fluid. Residual blood concentration was at 9.1 ng/mL, while no everolimus was observed in the pleural fluid. MANAGEMENT AND OUTCOME: Due to inefficacy of everolimus in this patient, she was switched to palbociclib and fulvestrant. CONCLUSION: Everolimus seems to have a poor diffusion in the pleural fluid.

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.

Impact of granulocyte colony-stimulating factor on FOLFIRINOX-induced neutropenia prevention: A population pharmacokinetic/pharmacodynamic approach.

AIMS: Granulocyte colony-stimulating factor (G-CSF) is frequently prescribed to prevent chemotherapy-induced neutropenia, but the administration schedule remains empirical in case of bimonthly chemotherapy such as FOLFIRINOX regimen. This pharmacokinetic/pharmacodynamic (PK/PD) study was performed to determine the effect of different G-CSF regimens on the incidence and duration of neutropenia following FOLFIRINOX administration in order to propose an optimal G-CSF dosing schedule. METHODS: A population PK/PD model was developed to describe individual neutrophil time course from absolute neutrophil counts (ANC) obtained in 40 advanced cancer patients receiving FOLFIRINOX regimen. The structural model considered ANC dynamics, neutropenic effect of cytotoxics and the stimulating effect of G-CSF on neutrophils. Final model estimates were used to simulate different G-CSF dosing schedules for 1000 virtual subjects. The incidence and duration of neutropenia were then calculated for different G-CSF dosing schedules. RESULTS: The final model successfully described the myelosuppressive effect induced by the 3 cytotoxics for all patients. Simulations showed that pegfilgrastim administration reduced the risk of severe neutropenia by 22.9% for subjects with low ANC at the start of chemotherapy. Median duration in this group was also shortened by 3.1 days when compared to absence of G-CSF. Delayed G-CSF administration was responsible for higher incidence and longer duration of neutropenia compared to absence of administration. CONCLUSION: The PK/PD model well described our population's ANC data. Simulations showed that pegylated-G-CSF administration 24 hours after the end of chemotherapy seems to be the optimal schedule to reduce FOLFIRINOX-induced neutropenia. We also underline the potential negative effect of G-CSF maladministration.

Therapeutic drug monitoring as a tool to optimize 5-FU-based chemotherapy in gastrointestinal cancer patients older than 75 years.

AIMS: Most clinical trials exclude elderly people, leading to a limited understanding of the benefit-to-risk ratio in this population. Despite existing data regarding the oncological management of elderly receiving fluorouracil (5-FU)-based regimen, our objective was to investigate 5-FU exposure/toxicity relationship in patients ≥75 years and compare the effectiveness of 5-FU therapeutic drug monitoring between elderly and younger patients. METHODS: Hundred fifty-four patients (31 of whom are older than 75 years) with gastrointestinal cancers, who were to receive 5-FU-based regimens, were included in our study. At cycle 1 (C1), the 5-FU dose was calculated using patient's body surface area, then a blood sample was drawn to measure 5-FU concentration and 5-FU dose was adjusted at the subsequent cycles based on C1 concentration. Assessments of toxicity were performed at the beginning of every cycle. RESULTS: Seventy-one percent of elderly patients required dose adjustments after C1, compared with 50% for younger patients. Percentages of patients within 5-FU area under the curve range at cycle 2 were 64% and 68%, respectively, for elderly and younger patients. The proportion of elderly patients experiencing severe toxicities fell from 15% at C1 to only 5% at cycle 3. CONCLUSION: Pharmacokinetic-guided 5-FU-dosing algorithm, leading to an improved tolerability while remaining within therapeutic concentration range, is even more valuable for patients older than 75 years than in younger patients.