Study of Estrogen Levels in Premenopausal Women Who Have Undergone Surgery for Breast Cancer and Are Receiving Triptorelin and Tamoxifen Citrate or Exemestane on Clinical Trial IBCSG 24-02

RATIONALE: Studying samples of blood from patients with breast cancer in the laboratory may help doctors learn how well triptorelin given together with tamoxifen citrate or exemestane works in lowering estrogen levels. PURPOSE: This clinical trial is studying estrogen levels in premenopausal women who have undergone surgery for breast cancer and are receiving triptorelin and tamoxifen citrate or exemestane on clinical trial IBCSG-2402.

OBJECTIVES: Primary * Describe estrogen levels (estradiol \[E2\], estrone \[E1\], and estrone sulphate \[E1S\]) at different time points during the first 4 years of treatment with triptorelin in combination with either tamoxifen citrate or exemestane on clinical trial IBCSG-2402 in premenopausal women with resected breast cancer. * Assess whether there is a suboptimally estrogen-suppressed subgroup of patients who receive exemestane. Secondary * Compare estrogen levels (E2, E1, E1S) at different time points during treatment with triptorelin in combination with either tamoxifen citrate or exemestane. * Examine potential predictive factors of ineffective estrogen suppression (e.g., age, chemotherapy \[yes/no\], type of chemotherapy received, smoking history, BMI, and evidence of menses at study entry). * Investigate the predictive value of optimal estrogen suppression during the first 6 and 12 months of treatment with regard to long-term estrogen suppression (4-year period). * Compare disease-free survival of suboptimally estrogen-suppressed patients treated with exemestane with that of patients with optimal suppression (exploratory analysis). * Examine related endocrine function (FSH and LH) to further elucidate causes of suboptimal estrogen suppression. OUTLINE: This is a multicenter study. Blood samples are collected at baseline and at 3, 6, 12, 18, 24, 36, and 48 months for measurement of estrogen levels (estradiol \[E2\], estrone \[E1\], and estrone sulphate \[E1S\]) by gas chromatography-mass spectrometry and measurement of endocrine function (FSH and LH).