Side effects associated with ultrarapid cytochrome P450 2D6 genotype among women with early stage breast cancer treated with tamoxifen.

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.

Prospective study on prognostic significance of DNA ploidy and Ki-67 expression in colorectal cancer.

The aim of the study was to correlate tumoral DNA ploidy and Ki-67 expression with therapy response, Overall Survival (OS), Disease Specific Survival (DSS) and Disease Free Survival (DFS). Three samples of colorectal cancer were collected from each patient. One sample of normal tissue was our internal control. DNA ploidy was evaluated by FACSCalibur cytometer and Ki-67 by immunohistochemistry. We studied 67 patients and we found aneuploidy in 65,7 percent of carcinoma with a Ki-67 median expression of 55 percent. After surgery and chemotherapy in 35 percent of the patients with aneuploid carcinoma and high proliferative activity (Ki-67 greater than 55 percent) there were no evidence of disease versus 100 percent of patients with DNA diploidy and low proliferative activity (Ki-67 less than 55 percent). Tumoral aneuploidy significantly correlated with lower OS, DSS and DFS (18 percent vs 86 percent at 30 months). Univariated analysis demonstrated a significant correlation between aneuploidy and develop disease progression (p=0,033, odd ratio=5.7), while the cut-off of 55 percent for Ki-67 expression did not correlate with OS, DSS and DFS. Preliminary results (the study is still in progress) seemed to suggest that DNA ploidy has a prognostic and predictive significance in colorectal carcinoma.