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Browsing by Subject "Hormonal Antineoplastic Agents"
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Item Cytochrome P450 2D6 activity predicts discontinuation of tamoxifen therapy in breast cancer patients(Springer Nature, 2009-08) Rae, J. M.; Sikora, M. J.; Henry, N. L.; Li, L.; Kim, S.; Oesterreich, S.; Skaar, Todd C.; Nguyen, A. T.; Desta, Z.; Storniolo, A. M.; Flockhart, David A.; Hayes, D. F.; Stearns, V.The selective estrogen receptor modulator tamoxifen is routinely used for treatment and prevention of estrogen-receptor-positive breast cancer. Studies of tamoxifen adherence suggest that over half of patients discontinue treatment before the recommended 5 years. We hypothesized that polymorphisms in CYP2D6, the enzyme responsible for tamoxifen activation, predict for tamoxifen discontinuation. Tamoxifen-treated women (n=297) were genotyped for CYP2D6 variants and assigned a ‘score’ based on predicted allele activities from 0 (no activity) to 2 (high activity). Correlation between CYP2D6 score and discontinuation rates at 4 months was tested. We observed a strong nonlinear correlation between higher CYP2D6 score and increased rates of discontinuation (r2=0.935, P=0.018). These data suggest that presence of active CYP2D6 alleles may predict for higher likelihood of tamoxifen discontinuation. Therefore, patients who may be most likely to benefit from tamoxifen may paradoxically be most likely to discontinue treatment prematurely.Item Lack of association between oestrogen receptor polymorphisms and change in bone mineral density with tamoxifen therapy.(Springer Nature, 2010-01-19) Henry, N. L.; Nguyen, A.; Azzouz, F.; Li, L.; Robarge, J.; Philips, S.; Cao, D.; Skaar, Todd C.; Rae, J. M.; Storniolo, A. M.; Flockhart, David A.; Hayes, D. F.; Stearns, V.BACKGROUND: Tamoxifen, a selective oestrogen receptor (ER) modulator, increases bone mineral density (BMD) in postmenopausal women and decreases BMD in premenopausal women. We hypothesised that inherited variants in candidate genes involved in oestrogen signalling and tamoxifen metabolism might be associated with tamoxifen effects in bone. METHODS: A total of 297 women who were initiating tamoxifen therapy were enrolled in a prospective multicentre clinical trial. Lumbar spine and total hip BMD values were measured using dual-energy X-ray absorptiometry (DXA) at baseline and after 12 months of tamoxifen therapy. Single-nucleotide polymorphisms (SNPs) in ESR1, ESR2, and CYP2D6 were tested for associations in the context of menopausal status and previous chemotherapy, with a mean percentage change in BMD over 12 months. RESULTS: The percentage increase in BMD was greater in postmenopausal women and in those patients who had been treated with chemotherapy. No significant associations between tested SNPs and either baseline BMD or change in BMD with 1 year of tamoxifen therapy were detected. CONCLUSION: The evaluated SNPs in ESR and CYP2D6 do not seem to influence BMD in tamoxifen-treated subjects.