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Title: Side effects associated with ultrarapid cytochrome P450 2D6 genotype among women with early stage breast cancer treated with tamoxifen. Author: Rolla R, Vidali M, Meola S, Pollarolo P, Fanello MR, Nicolotti C, Saggia C, Forti L, Agostino FD, Rossi V, Borra G, Stratica F, Alabiso O, Bellomo G. Journal: Clin Lab; 2012; 58(11-12):1211-8. PubMed ID: 23289191. Abstract: BACKGROUND: The side effects of tamoxifen, a drug widely used for the treatment and the prevention of recurrence in patients with estrogen receptor positive breast cancers (ER+), have been reported in clinical trials, but to date no information is available on their possible association with an increased enzymatic activity of CYP2D6 (ultra-metabolizers, UMs). The aim of this study was therefore to evaluate the association between the presence of multiple functional CYP2D6 alleles and the occurrence of side effects. METHODS: 61 women with ER+ breast cancer receiving tamoxifen monotherapy were investigated in order to assess the relationships between CYP2D6 UM phenotype and side effects. Genotyping of 16 CYP2D6 polymorphisms was performed using a new DNA microarray technology. RESULTS: A highly significant difference was detected (41.2% of difference, 95% CI 6 - 61%, Fisher's exact test, p = 0.030) between the numbers of Ultrarapid Metabolizer patients (UM; high activity) with two or more adverse drug reactions to tamoxifen (7/9; 77.8%), compared to the number of Extensive Metabolizers (EM; normal activity), Intermediate Metabolizers (IM; reduced activity), and Poor Metabolizers (PM; no activity) with at least two side effects (19/52, 36.5%). A similar difference was also observed comparing the two groups (UM vs EM-IM-PM) for the number of side effects (median and inter quartile range, IQR: AM/EM/IM 1, IQR 0-2 vs. ULTRA 2, IQR 2-4; Mann-Whitney p = 0.005). CONCLUSIONS: Our results suggest a new association between CYP2D6 gene duplication and side effects to tamoxifen, indicating a possible role of CYP2D6 in their occurrence.[Abstract] [Full Text] [Related] [New Search]