ABSTRACT
BACKGROUND: Previous studies evaluating the effect of cytochrome P450 2D6 (CYP2D6) polymorphisms on outcomes of adjuvant tamoxifen therapy have been conflicting due to differences in study design, concomitant medications that alter CYP2D6 metabolism, and tamoxifen adherence. METHODS: The authors performed CYP2D6 genotyping from whole blood and fresh frozen tumor samples (n 106) in patients at The University of Texas MD Anderson Cancer Center who were receiving, or had received, tamoxifen as adjuvant therapy for early breast cancer (EBC), using the AmpliChip CYP450 Test. Each patient's medical history was assessed for drugs that affected CYP2D6. Fifty-five patients who had experienced breast cancer recurrence were matched (by date of diagnosis, menopausal status, clinical stage [TNM Staging System], and race) to patients without recurrence. RESULTS: Unadjusted for other patient characteristics, the odds ratio for disease recurrence associated with CYP2D6 functional status was 1.0 (95% confidence interval, 0.35-2.85). After adjustment for stage, CYP2D6 inhibitors (moderate or strong vs none), and follow-up time, no significant association was found between CYP2D6 genotype and breast cancer recurrence in patients who were treated with adjuvant tamoxifen for EBC. CONCLUSIONS: This case-control study demonstrated no significant effect of CYP2D6 genotype on risk of recurrence in breast cancer patients who received adjuvant tamoxifen therapy.
