Factors Affecting Tamoxifen Metabolism in Patients With Breast Cancer: Preliminary Results of the French PHACS Study.

In addition to the effect of cytochrome P450 (CYP) 2D6 genetic polymorphisms, the metabolism of tamoxifen may be impacted by other factors with possible consequences on therapeutic outcome (efficacy and toxicity). This analysis focused on the pharmacokinetic (PK)-pharmacogenetic evaluation of tamoxifen in 730 patients with adjuvant breast cancer included in a prospective multicenter study. Plasma concentrations of tamoxifen and six major metabolites, the genotype for 63 single-nucleotide polymorphisms, and comedications were obtained 6 months after treatment initiation. Plasma concentrations of endoxifen were significantly associated with CYP2D6 diplotype (P < 0.0001), CYP3A4*22 genotype (P = 0.0003), and concomitant intake of potent CYP2D6 inhibitors (P < 0.001). Comparison of endoxifen levels showed that the CYP2D6 phenotype classification could be improved by grouping intermediate metabolizer (IM)/IM and IM/poor metabolizer diplotype into IM phenotype for future use in tamoxifen therapy optimization. Finally, the multivariable regression analysis showed that formation of tamoxifen metabolites was independently impacted by CYP2D6 diplotype and CYP3A4*22, CYP2C19*2, and CYP2B6*6 genetic polymorphisms.

Pathological and clinical response of a primary chemotherapy regimen combining vinorelbine, epirubicin, and paclitaxel as neoadjuvant treatment in patients with operable breast cancer.

This phase II study investigated the efficacy and tolerability of a primary chemotherapy regimen combining vinorelbine, epirubicin, and paclitaxel (VEP protocol) in women with stage II/III operable breast cancer. Patients (n = 50) were treated with six cycles of VEP according to the following schedule: vinorelbine (Navelbine); Pierre Fabre, Boulogne, France; http://www.pierre-fabre.com) 20 mg/m2, epirubicin (Farmorubicin; Pharmacia, New York, NY; http://www.pnu.com) 35 mg/m2 given on days 1 and 8, paclitaxel (Taxol; Bristol-Myers Squibb, New York, NY; http://www.bmsoncology.com) 175 mg/m2 given on day 9, and G-CSF 5 mg/kg/day given on days 10-20 of a 21-day cycle, followed by surgery and radiotherapy. After six cycles of VEP, the pathological response rate (pCR) in breast was confirmed in six patients (12%; 95% confidence interval [CI]: 3-21)) using Chevallier's classification and in nine patients (18%; 95% CI: 7.4-28.6) using Sataloff's classification. The clinical response rate was 42% (95% CI: 28.3-55.7), including 26% complete responses. Breast conservation was achieved in 68% of patients. After a median follow-up of 48 months (range, 34-62 months), 16 relapses were observed. The overall and disease-free survivals at 5 years were 54.1% (95% CI: 40.3-67.9) and 38% (95% CI: 24.1-51.9), respectively. The principal toxicities of VEP were grade 3/4 neutropenia observed in 30% of patients and grade 3 anemia observed in 12% of patients. There was no case of severe cardiac toxicity, thrombocytopenia, or any other serious adverse events. In conclusion, whereas this regimen was relatively well tolerated, it appears inferior to other regimens and its use is not recommended.