Docosahexaenoic Acid in Preventing Recurrence in Breast Cancer Survivors

Inclusion Criteria:

- Participants must have a history of histologically-confirmed stage I-III invasive breast cancer or ductal carcinoma in situ (DCIS), Paget's disease, lobular carcinoma in situ (LCIS), or proliferative benign breast disease

- No evidence of disease (in situ or invasive cancer that would normally be treated by resection) at trial entry as determined by the investigator

- >= 6 months from all previous breast cancer treatment (including surgery for invasive cancer, chest wall radiotherapy, chemotherapy, trastuzumab and endocrine therapy)

- Participants must have a body mass index (BMI) >= 25, defined as (weight in kilograms/[height in meters]^2)

- Participants must have adequate accessible breast tissue as determined by the treating physician, consisting of one breast unaffected by invasive cancer, which has not been radiated; a history of prior pre-invasive breast cancer or benign biopsy of this breast will be permitted

- Daily DHA consumption =< 200 mg/day in the month prior to screening estimated by an abbreviated DHA food frequency questionnaire

- Mammogram within no more than 6 months prior to the date of informed consent (normal/benign Breast Imaging-Reporting and Data System [BI-RADS] 1 or 2) and no further routine breast imaging planned during the course of the study (12 weeks DHA/placebo)

- Eastern Cooperative Oncology Group (ECOG) performance status must be =< 2 (Karnofsky >= 60%)

- Absolute neutrophil count >= 1,500/uL

- Platelets >= 75,000/uL

- White blood cells >= 3,000/uL

- Hemoglobin >= 10 g/dL

- Total bilirubin within 1.5 times the institution's upper limit of normal (ULN)

- Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) within 1.5 times the institution's ULN

- Serum creatinine within 1.5 times the institution's ULN

- Pregnant women will be excluded; for women of childbearing potential; negative pregnancy testing within 72 hours prior to or on study visit #1 (day 0) and willingness to use adequate contraception during the study intervention OR post-menopausal defined as any one of the following 1) prior hysterectomy, 2) absence of menstrual period for 1 year in the absence of prior chemotherapy or 3) absence of menstrual period for 2 years in women with a prior history of chemotherapy exposure who were pre-menopausal prior to chemotherapy

- Willingness to comply with all study interventions and follow-up procedures including the ability to swallow the study drug

- Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

- Any type of active invasive cancer (excluding breast and non-melanoma skin cancer) within the preceding 18 months

- A history of histologically-confirmed bilateral invasive breast cancer

- Bilateral mastectomy

- Prior history or evidence of metastatic breast cancer

- Prior radiation therapy to the contralateral (unaffected) breast

- Prior history of contralateral (unaffected) breast augmentation with breast implant placement

- History of daily use of aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) in the week preceding study entry

- History of DHA supplementation > 200 mg/day in the month preceding study entry

- History of autoimmune disorder or any illness that requires therapy with chronic steroids or immunomodulators

- History of therapeutic doses of anticoagulants including warfarin and low molecular weight heparin (e.g. for prior deep venous thrombosis and pulmonary embolism) in the preceding year

- Participants may not be receiving any other investigational agents during the study

- Women who have received cancer surgery, chemotherapy, biological therapy (e.g., trastuzumab), or radiotherapy for the treatment of any cancer within 6 months of study participation

- Women who are receiving endocrine therapy for breast cancer treatment or chemoprevention including tamoxifen, letrozole, anastrozole, fulvestrant, or exemestane at the time of screening

- Individuals with severe underlying chronic illness, such as uncontrolled diabetes; ongoing or active infection, psychiatric illness or social situations which in the opinion of the investigator would interfere with study participation

- History of allergic reactions attributed to compounds of similar chemical or biologic composition to DHA or corn/soy oil in placebo agent

- Pregnant, breastfeeding, or women of childbearing potential unwilling to use a reliable contraceptive method