RATIONALE: Studying samples of urine in the laboratory from women with breast cancer may help doctors learn whether tamoxifen and aromatase inhibitors alter the metabolism of estrogens.

PURPOSE: This clinical trial is studying the effect of tamoxifen or an aromatase inhibitor on estrogen metabolism in women undergoing treatment for newly diagnosed breast cancer.

OBJECTIVES:

• Learn the effects of selected chemotherapy agents on the profile of estrogen metabolites, glutathione conjugates, and depurinating DNA adducts in urine from women with breast cancer.
• Determine whether tamoxifen citrate or aromatase inhibitor alters the metabolism of estrogens.

OUTLINE: Patients are stratified according to planned therapy (tamoxifen citrate vs aromatase inhibitor).

Patients receive tamoxifen citrate or an aromatase inhibitor as planned. Urine samples (and nipple aspirate fluid, if possible) are collected before beginning treatment and after 2-6 months of treatment. Samples are analyzed for 40 estrogen metabolites, conjugates, and depurinating DNA adducts by ultraperformance liquid chromatography with tandem mass spectrometric detection.

Patients' information, including race, body mass index, age at menarche, menopausal status, age at menopause if applicable, smoking history, alcohol consumption, pregnancy history including age at each pregnancy, lactation, history of benign breast disease, hysterectomy, and disease type, is collected through medical record review.

Inclusion Criteria:

• Newly diagnosed ductal carcinoma in situ or invasive breast cancer
• Scheduled to receive tamoxifen citrate or an aromatase inhibitor
• Estrogen receptor or progesterone receptor positive
• ECOG performance status 0, 1, or 2

Exclusion Criteria:

• Not pregnant or nursing
• No prior antiestrogen drug such as tamoxifen citrate or raloxifene
• No concurrent estrogens

Women newly diagnosed with breast cancer that will be given tamoxifen or an aromatase inhibitor for therapeutic reasons.