S0927:Omega3-Fatty Acid Supp in Treating Muscle&Bone Pain&Stiffness in Pts W/Stg I,II,III Brst Canc Rec'v Hormone Thpy

DISEASE CHARACTERISTICS: * Histologically confirmed primary invasive adenocarcinoma of the breast * Stage I, II, or IIIA disease * No metastatic disease * Must have undergone modified radical mastectomy or breast-sparing surgery and recovered * Estrogen-receptor positive (ER+) and/or progesterone-receptor positive (PR+) * Currently taking a third-generation aromatase inhibitor (AI) \[e.g., anastrozole (Arimidex®), letrozole (Femara®), or exemestane (Aromasin®)\] for ≥ 90 days prior to registration with plans to continue for ≥ 180 days after registration * Must have completed the S092 Brief Pain Inventory (BPI)-Short Form within the past 14 days, and must have a worst pain/stiffness of ≥ 5 on the BPI (item #2) that has started or increased with AI therapy PATIENT CHARACTERISTICS: * Postmenopausal * Zubrod performance status 0-2 * Willing to submit blood for serum-free estradiol, total estradiol, serum inflammatory markers (IL6, TNF-α, CRP), DHA and EPA, lipid profile (LDL, HDL, triglycerides), and DNA analysis (CYP19A1) * Able to complete study questionnaires in English * At least 5 years since other malignancy except adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, ductal carcinoma in situ of the breast or adequately treated stage I or II cancer from which the patient is currently in complete remission * Patients must not have a known allergy to soy, given that the placebo is suspended in soybean oil PRIOR CONCURRENT THERAPY: * Se…