2504 Background: Epirubicin (EPI) is widely used to treat breast cancer. EPI is predominantly metabolized by uridine glucuronosyltransferase (UGT) 2B7 to inactive glucuronides. We previously showed that a UGT enhancer single nucleotide polymorphism (SNP) at position -161 T to C correlated with rates of morphine glucuronidation.
METHODS
We performed a prospective pharmacogenetic study of effects of this SNP on EPI metabolism in M0 breast cancer patients (PTS) receiving adjuvant or neoadjuvant FEC100 (5-fluorouracil 500 mg/m2, EPI 100 mg/m2 and cyclophosphamide 500 mg/m2) given every 3 wks. PTS with ALT and AST ≤ upper limit of normal (ULN), a total bilirubin ≤ ULN, and normal renal and cardiac function were eligible. EPI levels were drawn at approximately 1 and 24 hrs. Cycle 1 toxicities were assessed using NCIC CTG toxicity criteria.
RESULTS
123 PTS entered this study, mean (range): age 51 (28 - 74), sex 122 F/ 1 M, baseline AST 24 U/L (13-66), ALT 22 U/L (5-90), bilirubin 8 μmol/L (2-26), creatinine 74 μmol/L (50 - 126). PTS were genotyped using Pyrosequencing; 26 PTS were TT homozygotes, 59 were CT heterozygotes, and 33 were CC homozygotes. 5 PTS could not be genotyped. A three compartment population pharmacokinetic model in NONMEM V 1.1 for EPI was used incorporating all PTS. The baseline objective function was 1817, and inclusion of genotype significantly improved the objective function to 1764; CC genotype PTS had decreased EPI clearance 88.9 L/hr compared to CT/TT genotype PTS 129 L/hr, p<0.001. Rates of first cycle grade 3/4 leucopenia were 78% in CC PTS and 48% in CT/TT PTS; consistent with the pharmacokinetic analysis.
CONCLUSIONS
A SNP in UGT 2B7 is common and appears to predicts EPI clearance and myelosuppresion in non-metastatic breast cancer PTS and may form the basis for a method to individualize EPI treatment. No significant financial relationships to disclose.