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Medline ® Abstract for Reference 120

of 'Dosing of anticancer agents in adults'

120
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The role of UGT1A1*28 polymorphism in the pharmacodynamics and pharmacokinetics of irinotecan in patients with metastatic colorectal cancer.
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Toffoli G, Cecchin E, Corona G, Russo A, Buonadonna A, D'Andrea M, Pasetto LM, Pessa S, Errante D, De Pangher V, Giusto M, Medici M, Gaion F, Sandri P, Galligioni E, Bonura S, Boccalon M, Biason P, Frustaci S
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J Clin Oncol. 2006;24(19):3061.
 
PURPOSE: UGT1A1*28 polymorphism has been associated with decreased glucuronidation of SN38, the active metabolite of irinotecan. This could increase toxicity with this agent.
PATIENTS AND METHODS: In a prospective study, 250 metastatic colorectal cancer patients were treated with irinotecan, fluorouracil, and leucovorin as first-line treatment. UGT1A1*28 polymorphism was investigated with respect to the distribution of hematologic and nonhematologic toxicity, objective response rate, and survival. Pharmacokinetics was investigated in a subgroup of patients (71 of 250) who had been analyzed with respect to toxicity and efficacy.
RESULTS: UGT1A1*28 polymorphism was associated with a higher risk of grade 3 to 4 hematologic toxicity (odds ratio [OR], 8.63; 95% CI, 1.31 to 56.55), which was only relevant for the first cycle, andwas not seen throughout the whole treatment period for patients with both variant alleles TA7/TA7 compared with wild-type TA6/TA6. The response rate was also higher in TA7/TA7 patients (OR, 0.32; 95% CI, 0.12 to 0.86) compared with TA6/TA6. A nonsignificant survival advantage was observed for TA7/TA7 when compared with TA6/TA6 patients (hazard ratio, 0.81; 95% CI, 0.45 to 1.44). Higher response rates were explained by a different pharmacokinetics with higher biliary index [irinotecan area under the curve (AUC)x(SN38 AUC/SN38G AUC)]and lower glucuronidation ratio (SN38G AUC/SN38 AUC) associated with the TA7/TA7 genotype and a higher response rate, indicating that the polymorphism is functionally relevant.
CONCLUSION: The results indicate that UGT1A1*28 polymorphism is of some relevance to toxicity; however, it is less important than discussed in previous smaller trials. In particular, the possibility of a dose reduction for irinotecan in patients with a UGT1A1*28 polymorphism is not supported by the result of this analysis.
AD
Experimental and Clinical Pharmacology Unit, Medical Oncology unit of Centro di Riferimento Oncologico, National Cancer Institute, via Pedemontana Occidentale, 12, 33081, Aviano, Italy. gtoffoli@cro.it
PMID