Predicting 5-fluorouracil toxicity in colorectal cancer patients from peripheral blood cell telomere length: a multivariate analysis.

BACKGROUND: Identifying various pretreatment factors that predict chemotherapy-induced toxicity in colorectal cancer (CRC) patients undergoing treatment for their disease is crucial to optimising patient care. METHODS: Seventy-three patients received adjuvant 5-fluorouracil (5FU)/leucovorin using either the Mayo Clinic (n=42) or a weekly schedule (n=31) and evaluated for clinical toxicity. Pretreatment blood analysis included measures of plasma uracil and dihydrouracil, peripheral blood mononuclear cell (PBMNC) telomere length (TL), standard biochemistry and cell differential analysis. On the first day of treatment 5FU-pharmacokinetic variables of area under the curve, half life and clearance were also measured. These variables together with age and gender were used in univariate and multivariate analysis as predictors of clinical toxicity. RESULTS: For the Mayo schedule the primary toxicities were neutropenia (69%), mucositis (58%) and leukopenia (46%), with 70% of patients presenting with haematological toxicity ≥grade 1 (neutropenia and/or leukopenia). Multivariate analysis showed that haematological toxicity was predicted by short TL, high platelet lymphocyte ratio (PLR) and low neutrophil count (R(2)=0.38, P<0.0006), whereas mucositis was predicted by age, TL and PLR (R(2)=0.34, P<0.001). For the weekly schedule diarrhoea predominated (16%), with female gender as the only predictive factor. Although measures of uracil metabolism correlated well with 5FU metabolism (r=0.45-0.49), they did not indicate abnormal pyrimidine metabolism in this cohort and not surprisingly failed to predict for 5FU toxicity. CONCLUSION: Short TL of PBMNC and an increased PLR were strong predictors of mucositis and haematological toxicity in CRC patients undergoing 5FU treatment in the adjuvant setting.

Association of thymidylate synthase enhancer region polymorphisms with thymidylate synthase activity in vivo.

Two known polymorphisms in the 5' enhancer region (ER) of the thymidylate synthase (TS) gene, a variable number of tandem repeats of a 28 bp sequence (2R/3R) and a further G>C single nucleotide substitution within the repeats, result in genotypes with 0-5 functional upstream stimulatory factor (USF) E-box consensus elements. However, the relationship between these polymorphisms, regulation of TS expression and patient response to fluoropyrimidine treatment has been inconsistent. In this study, seven possible TSER allele configurations showed similar patterns of luciferase gene expression regardless of cell type or USF-1 content, with no significant difference in promoter activity between the wild-type 2RGC and 3RGGC (1.40±0.37 vs 1.43±0.32, P=0.90), whereas the minor alleles, 2RCC and 3RGCC, were significantly reduced (0.84±0.17, P=0.01) and increased (3.19±0.72, P=0.001) respectively. Patient plasma levels of 2'-deoxyuridine, a surrogate marker of TS activity, were significantly different between genotypes (P<0.001) and inversely related to luciferase activity (P=0.02) but not to the absolute number of functional repeated elements (P=0.16), suggesting that the position, rather than the number of functional USF E-box repeats in the TSER, is responsible for determining gene expression in vitro and TS activity in vivo.

Phase I and pharmacokinetic study of docetaxel in combination with epirubicin and cyclophosphamide in advanced cancer: dose escalation possible with granulocyte colony-stimulating factor, but not with prophylactic antibiotics.

BACKGROUND: The objective of this phase I trial was to determine the maximally tolerated doses of the combination of docetaxel, epirubicin and cyclophosphamide. PATIENTS AND METHODS: Patients with advanced cancer, World Health Organization (WHO) performance status 0 to 2, who had received up to one prior chemotherapy regimen were treated with docetaxel, epirubicin and cyclophosphamide repeated every 21 days. The cyclophosphamide dose was fixed at 600 mg/m(2) and the dose levels studied were: docetaxel/epirubicin; 60/60, 75/60, 75/75, 75/90, 85/90 and 85/105 mg/m(2). There was provision for the addition of prophylactic ciprofloxacin and granulocyte colony-stimulating factor (G-CSF) in separate steps if dose-limiting toxicity (DLT) was neutropenia related. RESULTS: Forty-three patients were entered and all were assessable for toxicity. Dose-limiting toxicity, predominantly febrile neutropenia, was surprisingly seen at the first dose level. The addition of prophylactic ciprofloxacin did not permit dose escalation, but dose escalation was possible with the addition of G-CSF. The highest administered dose level with G-CSF was docetaxel 85 mg/m(2) and epirubicin 105 mg/m(2) with DLTs in five of six patients. Treatment was well tolerated in 10 patients treated at the recommended dose level (85/90) with only one patient experiencing DLT. Responses were seen in a range of malignancies including breast and anaplastic thyroid cancers. No significant pharmacokinetic interaction was observed, but a transient increase in epirubicinol plasma concentration occurred during and after docetaxel infusion. CONCLUSIONS: The recommended dose level of docetaxel 85 mg/m(2), epirubicin 90 mg/m(2) and cyclophosphamide 600 mg/m(2) with G-CSF support has a favorable toxicity profile and is suitable for further investigation in phase II and III trials.

Simple and sensitive high-performance liquid chromatography method for the determination of docetaxel in human plasma or urine.

Several methods for quantification of docetaxel have been described mainly using HPLC. We have developed a new isocratic HPLC method that is as sensitive and simpler than previous methods, and applicable to use in clinical pharmacokinetic analysis. Plasma samples are spiked with paclitaxel as internal standard and extracted manually on activated cyanopropyl end-capped solid-phase extraction columns followed by isocratic reversed-phase HPLC and UV detection at 227 nm. Using this system, the retention times for docetaxel and paclitaxel are 8.5 min and 10.5 min, respectively, with good resolution and without any interference from endogenous plasma constituents or docetaxel metabolites at these retention times. The total run time needed is only 13 min. The lower limit of quantification is 5 ng/ml using 1 ml of plasma. The validated quantitation range of the method is 5-1000 ng/ml with RSDs < or = 10%, but plasma concentrations up to 5000 ng/ml can be accurately measured using smaller aliquots. This method is also suitable for the determination of docetaxel in urine samples under the same conditions. The method has been used to assess the pharmacokinetics of docetaxel during a phase I/II study of docetaxel in combination with epirubicin and cyclophosphamide in patients with advanced cancer.

Simultaneous determination of dihydrofluorouracil and 5-fluorouracil in plasma by high-performance liquid chromatography.

Dihydrofluorouracil (FUH2) is the product of the first rate-limiting step in catabolism of 5-fluorouracil (5-FU), catalyzed by the enzyme dihydropyrimidine dehydrogenase. In humans, more than 80% of administered 5-FU is degraded through this catabolic pathway. The ability to measure FUH2 and 5-FU simultaneously may provide an index of the extent to which 5-FU is catabolized. A sensitive and efficient extraction and HPLC method has been developed for simultaneous measurement of FUH2 and 5-FU in patients' plasma. Trichloroacetic acid precipitation of plasma proteins was followed by extraction into ethyl acetate, evaporation under nitrogen, and reconstitution in phosphate buffer. The extract was analyzed by isocratic chromatography using a C18 reversed-phase column with uv detection at 268 nm (5-FU) and 220 nm (FUH2). The detection limit is 0.005 nmol on column for aqueous standards or 0.20 microM in 1 ml of plasma standards for both compounds. This method can be applied to pharmacokinetic studies of 5-FU in patients and may be useful as a means of assessing the activity of dihydropyrimidine dehydrogenase.