RATIONALE: Studying samples of blood in the laboratory from patients with breast cancer may help doctors learn more about changes that occur in DNA and identify biomarkers related to fatigue.

PURPOSE: This research study is studying biomarkers associated with fatigue in patients with early-stage breast cancer treated with metformin or placebo on NCIC-CTG-MA.32.

OBJECTIVES:

• To prepare, separate into components, and store the blood specimens at the NSABP Serum Bank at Baylor College of Medicine Breast Center for future DNA, RNA, and plasma analysis, and to analyze specific proinflammatory cytokines, genetic polymorphisms, and RNA expression arrays in collaborating laboratories at University of California, Los Angeles (UCLA).
• To examine the association between markers of inflammation and symptoms of fatigue among patients with and without exposure to metformin hydrochloride.
• To examine the relationship between single nucleotide polymorphism (SNPs) in the promoter regions of IL-1 and IL-6 and symptoms of fatigue with and without exposure to metformin hydrochloride.
• To examine RNA expression profiles in relationship to fatigue and compare the pattern of expression in patients with and without exposure to metformin hydrochloride.
• To determine the biological and behavioral predictors of fatigue in breast cancer patients in the five years post-randomization.
• To determine whether metformin is associated with reductions in inflammatory markers and corresponding decreases in fatigue. (Exploratory)

OUTLINE: This is a multicenter study.

Patients' serum and plasma, collected at baseline and at 6, 12, and 24 months after NCIC CTG MA.32 randomization, are analyzed for inflammatory markers, DNA polymorphisms, and RNA expression arrays by ELISA, TaqMan PCR, and RT-PCR.

Patients complete the Fatigue Symptom Inventory (symptoms associated with fatigue, sleep disturbance, depression, and endocrine therapy) at baseline and periodically during study.

Inclusion Criteria

• The patient must have consented to participate and must have signed and dated an appropriate IRB-approved consent form that conforms to federal and institutional guidelines for the MA.32.F Study before being enrolled.
• The patient must be female.
• The patient must reside in the United States or Canada.
• The patient must be English-speaking.
• The patient must be eligible for randomization in the MA.32 treatment trial. (Participation in the MA.32 QOL study is permitted but not required.)
• The patient must not have started taking MA.32 study therapy.
• The patient must have completed primary breast radiation therapy at least two weeks prior to enrollment in MA.32.F.

Exclusion Criteria

• MA.32 study therapy has been initiated.
• Currently receiving radiation therapy or additional radiation therapy is planned for initiation after starting MA.32 study therapy.

Patients with breast cancer who have been diagnosed and have undergone definitive surgical treatment for invasive breast cancer within the previous 12 months and who are eligible for randomization to NCIC MA.32.