The role of UGT1A1*28 polymorphism in the pharmacodynamics and pharmacokinetics of irinotecan in patients with metastatic colorectal cancer

J Clin Oncol. 2006 Jul 1;24(19):3061-8. doi: 10.1200/JCO.2005.05.5400.


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, and was 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.

Publication types

  • Clinical Trial
  • Multicenter Study

MeSH terms

  • Adult
  • Aged
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Camptothecin / adverse effects
  • Camptothecin / analogs & derivatives*
  • Camptothecin / pharmacokinetics
  • Camptothecin / pharmacology
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / pathology
  • Female
  • Fluorouracil / administration & dosage
  • Genotype
  • Glucuronosyltransferase / genetics*
  • Glucuronosyltransferase / metabolism
  • Humans
  • Irinotecan
  • Leucovorin / administration & dosage
  • Male
  • Middle Aged
  • Neoplasm Metastasis
  • Polymorphism, Genetic*
  • Prospective Studies
  • Treatment Outcome


  • Irinotecan
  • Glucuronosyltransferase
  • Leucovorin
  • Fluorouracil
  • Camptothecin