Omega-3 Fatty Acids in Preventing Breast Cancer in Women at High Risk of Developing Breast Cancer

DISEASE CHARACTERISTICS: * At increased risk of developing breast cancer, as defined by 1 of the following criteria: * 5-year Gail risk ≥ 1.7% * Calculated 5-year Gail risk ≥ 5 times the average for age group, as defined by 1 of the following: * At least 0.1% (for patients age 20-29) * At least 1.0% (for patients age 30-39) * At least 1.7% (for patients age 40 and over) * Known BRCA1 or BRCA2 mutation carrier * Family history consistent with hereditary breast cancer, as defined by any of the following: * At least 4 relatives diagnosed with breast cancer at any age * At least 2 first-degree relatives diagnosed with breast cancer at age 50 or younger * Breast and ovarian cancer diagnosed in the same relative * At least 2 occurrences of breast cancer and 1 occurrence of ovarian cancer at any age in the same family * Atypical hyperplasia or lobular carcinoma in situ of the breast by prior biopsy * History of unilateral ductal carcinoma in situ of the breast * History of invasive stage I breast cancer in remission (completed local and systemic standard therapy) * History of ovarian cancer in remission for \> 5 years * Baseline mammogram performed within the past 6 months with an interpretation of not suspicious for malignancy (BIRAD 1-3) * Not eligible for OR refused standard breast cancer risk reduction strategies (e.g., prophylactic oophorectomy, prophylactic mastectomy, or tamoxifen) PATIENT CHARACTERISTICS: Age * 18 and over Sex * Female Menopausal status * Not specified Performance status * SWOG 0-1 Life expectancy * Not specified Hematopoietic * Absolute granulocyte count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 8.0 g/dL Hepatic * SGOT and/or SGPT ≤ 2.5 times upper limit of normal (ULN) * Alkaline phosphatase ≤ 2.5 times ULN * Bilirubin ≤ 2.0 times ULN Renal * Creatinine ≤ 2.0 mg/dL Other * Not pregnant or nursing * Negative pregnancy test * No underlying medical, psychiatric, or social condition that would preclude study participation * No other invasive malignancy within the past 5 years except nonmelanoma skin cancer PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * Not specified Endocrine therapy * More than 6 months since prior and no concurrent hormonal therapy, including any of the following: * Antiestrogens * Estrogen * Selective estrogen-receptor modulators * Progestins * Aromatase inhibitors * Hormonal contraceptives Radiotherapy * Not specified Surgery * No prior bilateral mastectomy Other * More than 3 months since prior and no concurrent chronic (i.e., \> 3 times per week) non-steroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, or indomethacin) or cyclooxygenase-2 inhibitors * No prior cancer treatment that would preclude study treatment