Pharmacogenetics of Aromatase Inhibitors

OBJECTIVES:

• To evaluate the association of intragenic haplotypes in genes encoding proteins involved in anastrozole metabolism pathways with anastrozole steady state plasma levels in postmenopausal women with estrogen receptor-positive and/or progesterone receptor-positive stage I, II, or III breast cancer.
• To evaluate the association of intragenic haplotypes in genes that encode proteins involved in pathways for estrogen synthesis, metabolism, and transport and in genes involved in anastrozole metabolism with the pharmacodynamic (PD) effects of anastrozole therapy, as measured by changes (before vs after drug therapy) in plasma levels of estradiol, estrone, estrone sulfate, testosterone, and androstenedione in these patients.
• To evaluate the association of intragenic haplotypes described above with the PD effects of anastrozole therapy, as measured by changes in breast density and bone mineral density before and at 1 year after drug therapy.
• To collect and bank blood samples and mammographic, bone density, and questionnaire data from patients enrolled on CAN-NCIC-MA27 and randomized to receive exemestane.

OUTLINE: This is a multicenter study. Patients are stratified according to prior tamoxifen use (yes vs no).

Blood samples are obtained for pharmacogenetic studies at baseline, at 6-12 weeks, and then at 1 year. Samples are analyzed for plasma anastrozole concentrations via high-performance liquid chromatography; genotyping for htSNPs via PCR; plasma levels of estradiol, estrone, estrone sulfate, testosterone, and androstenedione via gas chromatographic negative chemical ionization tandem mass spectrometry and liquid chromatographic electrospray tandem mass spectrometry.

Mammograms are obtained at baseline (i.e., within the past 6 months) and at 1 year to assess breast density. Patients with bilateral disease, bilateral breast augmentation, or bilateral mastectomy do not participate in this portion of the study.