In irinotecan (CPT-11)-based chemotherapy, neutropenia and diarrhea are often induced. In the present study, the clinical significance of the concentration ratios of 7-ethyl10-hydroxycamptothecin (SN-38) glucuronide (SN-38G) and SN-38 in the plasma in predicting CPT-11induced neutropenia
was examined. A total of 17 patients with colorectal cancer and wild-type UDP-glucuronosyltransferase (UGT)1A1 gene were enrolled and treated with CPT-11 as part of the FOLFIRI regimen [CPT-11 and fluorouracil (5-FU)]. Blood was taken exactly 15 min following a 2-h continuous infusion of CPT-11.
Plasma concentrations of SN-38, SN-38G and CPT-11 were determined by a modified high-performance liquid chromatography (HPLC) method. The median, maximum and minimum values of plasma SN-38G/SN-38 ratios were 4.25, 7.09 and 1.03, respectively, indicating that UGT activities are variable among
patients with the wild-type UGT1A1 gene. The plasma SN-38G/SN-38 ratios decreased with an increase in the trial numbers of chemotherapy (r=0.741, p=0.000669), suggesting that CPT-11 treatment suppresses UGT activity, and the low plasma SN-38G/SN-38 ratios resulted in the induction of greater
neutropenia. However, in this analysis, 2 clearly separated regression lines were observed between plasma SN-38G/SN-38 ratios and neutropenia induction. In conclusion, UGT activity involved in SN-38 metabolism is variable among patients with the wild-type UGT1A1 gene, and each CPT-11 treatment
suppresses UGT activity. One-point determination of the plasma SN-38G/SN-38 ratio may provide indications for the prediction of CPT-11-induced neutropenia and adjustment of the optimal dose, although further studies are required.
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Document Type: Research Article
Department of Pharmacy, Osaka Rosai Hospital, Sakai, Osaka 591-8025, Japan
Department of Surgery, Osaka Rosai Hospital, Sakai, Osaka 591-8025, Japan
Laboratory of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmaceutical Sciences, Hiroshima International University, Kure, Hiroshima 737-0112, Japan
Publication date: January 1, 2012
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Oncology Letters is a monthly, peer-reviewed journal, available in print and online, that focuses on all aspects of clinical oncology, as well as in vitro and in vivo experimental model systems relevant to the mechanisms of disease.
The principal aim of Oncology Letters is to provide the prompt publication of original studies of high quality that pertain to clinical oncology, chemotherapy, oncogenes, carcinogenesis, metastasis, epidemiology and viral oncology in the form of original research, reviews and case reports.
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