Evaluation of Predictive Factors Regarding the Effectivity of Aromatase Inhibitor Therapy (PreFace)

Aromatase inhibitors have shown a superior efficacy compared to tamoxifen in the treatment of hormonal receptor positive breast cancer in postmenopausal patients. Side effects like osteoporosis, bone fractures and muscle/bone pain are however more frequent using of aromatase inhibitors compared with tamoxifen. These side effects compromise the patients' well being in a significant way and may favour the use of Tamoxifen in clinical practice. Furthermore there is evidence that polymorphisms in the CYP2D6 Gene might be associated with an improved efficacy of Tamoxifen that is equieffective to aromatase inhibitors. Concerning the pharmacogenetics of aromatase inhibition there are known polymorphisms of the CYP19A1 gene that are associated with altered peripheral sex hormone levels and altered prognosis in breast cancer patients. One study could even associate a polymorphism in the CYP19A1 gene with a prolonged time to progression in patients with metastatic breast cancer who have been treated with letrozol. Therefore the aim of this study is to identify biomarkers that could predict the efficacy of an adjuvant Letrozol treatment in postmenopausal breast cancer patients.