Evaluation of the Association Between CYP2D6 Genetic Polymorphisms and the Treatment Effect of Tamoxifen

A Clinical Study for the Evaluation of the Association Between CYP2D6 Genetic Polymorphisms and the Treatment Effect of Tamoxifen in Patients With Metastatic Breast Cancer

Primary objectives of this study is to evaluate the effects of CYP2D6 genotypes on time to progression after tamoxifen treatment in pre- or postmenopausal women with metastatic breast cancer. Furthermore, we will evaluate the effects of CYP2D6 genotypes on clinical benefit and response duration to tamoxifen administration in pre- or postmenopausal women with metastatic breast cancer and also evaluate the effects of CYP2D6 genotypes on the steady state plasma concentration of tamoxifen and its metabolites

Inclusion Criteria:

• Histologically or cytologically diagnosed stage IV or recurrent breast cancer patients according to American Joint Committee on Cancer (AJCC)
• Positive estrogen receptor or Positive progesterone receptor.
• Females at least 18 years of age.
• Prior radiation therapy is allowed as long as the irradiated area is not the only source of measurable disease
• Prior hormone therapy less than 2.
• No history of Megace medication for recent 28 days
• Performance status of 0, 1 and 2 on the ECOG criteria
• Clinically measurable disease, defined as bidimensionally measurable lesions with clearly defined margins on x-ray, CT scan, MRI or physical examination. Lesions serving as measurable disease must be at east 1 cm by 1 cm, as defined by x-ray, CT scan, MRI, or physical examination
• Bone only or pleural fluid only disease is included as long as evaluation for clinical benefit is possible
• Estimated life expectancy of at least 12 weeks
• Compliant patient who can be followed-up adequately.
• Adequate hematologic (WBC count 3,000/mm3, platelet count 100,000/mm3), hepatic (bilirubin level 1.8 mg/dL, AST, ALT 1.5xULN, albumin 2.5 g/dL), and renal (creatinine concentration 1.5 mg/dL) function.
• Informed consent from patient or patient's relative
• Childbearing women should use non-hormonal contraceptive method

Exclusion Criteria:

• Active or uncontrolled infection.
• Second primary malignancy (except in situ carcinoma of the cervix or adequately treated basal cell carcinoma of the skin or prior malignancy treated more than 5 years ago without recurrence).