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The present study aimed at investigating whether the simultaneous evaluation of pharmacokinetic, pharmacogenetic and demographic factors could improve prediction on toxicity and survival in colorectal cancer patients treated with adjuvant 5-fluorouracil (5FU)/leucovorin therapy. One hundred and thirty consecutive, B2 and C Duke's stage colorectal cancer patients were prospectively enrolled. 5FU pharmacokinetics was evaluated at the first cycle. Thymidylate synthase (TYMS) 5 0 UTR and 3 0 UTR polymorphisms and methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms were assessed in peripheral leukocytes. Univariate and multivariate analyses were applied to evaluate which variables could predict chemotherapy-induced toxicity, disease-free survival (DFS) and overall survival (OS). Multivariate analysis showed that: (a) low 5FU clearance was an independent predictive factor for severe toxicity (OR ¼ 7.32; Po0.0001); (b) high-5FU clearance predicted poorer DFS (HR ¼ 1.96; P ¼ 0.041) and OS (HR ¼ 3.37; P ¼ 0.011); (c) advanced age was associated with shorter DFS (HR ¼ 3.34; P ¼ 0.0008) and OS (HR ¼ 2.66; P ¼ 0.024); (d) the C/C genotype of the MTHFR C677T polymorphism was protective against grade 3 -4 toxicity (P ¼ 0.040); (e) none of the TYMS polymorphisms could explain 5FU toxicity or clinical outcome.

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A method for calculating the initial 5-FU dose is proposed which takes into account patient BW, gender and a target AUC of 596 mg x min/l. Nevertheless, it appears that a substantial part of 5-FU toxicity is not linked to pharmacokinetic factors and dose adjustments must still be on the basis of careful clinical surveillance.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Gemcitacine is taken up by the cell through various nucleoside transporters of either the concentrative (CNT) or equilibrative type (ENT) and is then transformed into the inactive metabolite, dFdU, by cytidine deaminase (CDA) and into the active metabolite, dFdCMP, by deoxycytidine kinase (dCK).• While the major contribution of CDA to gemcitabine elimination is well recognized no data about the role of CNT and ENT activities have yet been reported. Both nucleoside transporters exhibit genetic polymorphisms characterized by different expression levels or nucleoside affinity. WHAT THIS STUDY ADDS• The plasma clearance (CL) of gemcitabine has been determined following the standard 30 min infusion of 1000-1250 mg m -2 . The in vivo CDA activity was measured as end of infusion metabolic ratio (MR = dFdU : gembitabine) and the variant hCNT-1 and hENT-1 alleles were genotyped.• Our results confirmed that gemcitabine CL is directly correlated with CDA activity and inversely correlated with age and, for the first time, show that patients heterozygous for the -706 G > C hENT-1 mutation have a lower CL as compared with wild type patients. AIMGemcitabine (GEM) enters normal and tumour cells via concentrative (CNT) and equilibrative nucleoside transporters (ENT) and is subsequently deaminated to the inactive difluorodeoxyurine (dFdU) by cytidine deaminase (CDA). The aim of our study was to ascertain whether the nucleoside transporter genotype and the CDA activity phenotype can predict total GEM plasma clearance. METHODSForty-seven patients received GEM 1000-1250 mg m -2 i.v. over 30 min. Plasma concentrations of GEM and dFdU were measured and individual pharmacokinetic profiles were determined. CDA activity was measured ex vivo in plasma samples. The two most common hENT1 and hCNT1 polymorphisms were determined from genomic DNA. RESULTSMultivariate analysis revealed that GEM plasma clearance (CL) was positively correlated with the end of infusion dFdU : GEM ratio (P < 0.0001), which is a marker of in vivo CDA activity. The ENT1 genotype characterized by high transport capacity (G/G) and age were inversely correlated with CL (P = 0.027 and 0.048, respectively). A strong correlation was found between end of infusion GEM concentration and area under the concentration-time curve from time 0 to infinity (AUC(0,•)) (r 2 = 0.77). CONCLUSIONSOur results confirm the role of CDA and age on the interindividual variability of GEM CL and show the contribution of the hENT1 genotype for the first time.

Background Oral metronomic therapy (OMV) is particularly suitable for palliative care, and schedules adapted for unfit patients are advisable. This study investigated the effects of oral vinorelbine given every other day without interruption and its pharmacokinetic profile in patients with advanced lung cancer. Materials and Methods Ninety-two patients received OMV at doses of 20, 30 or 50 mg. Toxic events, clinical benefit and overall survival were analysed. Blood pharmacokinetics were evaluated in 82 patients. Results Median treatment duration and overall survival were 15 (range 1.3-144) and 32.3 weeks, respectively; fourty-eight (60%) patients experienced clinical benefit. Outcomes were unrelated to previous therapies, age, histology or comorbidities. Toxicity was associated with higher blood concentrations of the drug. Pharmacokinetics were stable for up to two years, and were not influenced by treatment line or age. Conclusions OMV produced non-negligible survival in patients and also showed stable long-term blood concentrations. The schedule of 20-30 mg every other day without interruption gave good tolerability and clinical benefit.