This phase II trial evaluates tamoxifen, with or without omega-3 fatty acids, for reducing risk of breast cancer among postmenopausal and overweight or obese women who are at increased risk of developing breast cancer. Tamoxifen is a selective estrogen receptor modulator. It works by blocking the effects of the hormone estrogen in the breast. Tamoxifen is approved by the Food and Drug Administration for prevention of breast cancer in women at increased risk. Omega-3 fatty acids have been shown to decrease the amount of fats made in the liver. Omega-3 fatty acids may work to prevent cancer in overweight or obese individuals. Tamoxifen with or without omega-3 fatty acids may be effective at reducing risk of breast cancer among women who are postmenopausal, overweight or obese, and at increased risk.
Age 45 - 74
Postmenopausal female
Postmenopausal is defined as either
Prior removal of the ovaries, or if ovaries intact amenorrhea for >= 12 months and not on any form of contraception, or
Bilateral breast implants (danger of implant puncture with RPFNA)
Prior invasive breast cancer
Prior invasive uterine cancer
Other prior invasive cancer and haven't completed cancer related therapy or with evidence of disease (other than non-melanoma skin cancer) within the past 2 years
Parallel
Biospecimen Collection
Procedure/SurgeryUndergo collection of blood samples
Mammography
Procedure/SurgeryUndergo mammography
Omega-3-Acid Ethyl Esters
DrugGiven PO
Questionnaire Administration
Other interventionAncillary studies
Random Periareolar Fine-Needle Aspiration
Procedure/SurgeryUndergo RPFNA
Tamoxifen
DrugGiven PO
Change in serum adiponectin
An analysis for difference between the two arms will be conducted to document a beneficial effect of addition of high dose omega-3 fatty acids to low dose tamoxifen. Paired and unpaired t-tests will be used.
Change in insulin resistance
Evaluated using Homeostatic Model Assessment of Insulin Resistance, as calculated using fasting glucose and fasting insulin. Paired and unpaired t-tests will be used. Spearman correlation between change in biomarkers will be estimated and compared across the study arms using Fisher's Z-transformed values.
Change in insulin sensitivity
Evaluated using Homeostatic Model Assessment of Insulin Sensitivity. Paired and unpaired t-tests will be used. Spearman correlation between change in biomarkers will be estimated and compared across the study arms using Fisher's Z-transformed values.
Change in insulin secretory function
Evaluated using Homeostatic Model Assessment of Beta Cell Function. Paired and unpaired t-tests will be used. Spearman correlation between change in biomarkers will be estimated and compared across the study arms using Fisher's Z-transformed values.
Estrogen response gene index (ERGI)
The estrogen response gene index reflects change in gene expression over time. The genes assayed for this index are: ESR1 (codes for estrogen receptor alpha), ESR2 (codes for estrogen receptor beta), GREB1 (codes for growth regulation by estrogen in breast cancer 1), PGR (codes for progesterone receptor) and TFF1 (also known as pS2, which codes for trefoil factor 1). The log2-transformed values of the ratio of relative abundance (6-month value: baseline value) for GREB1, PGR, TFF1, and the ratio of ESR1:ESR2 are averaged to produce the ERGI. Paired and unpaired t-tests will be used. Spearman correlation between change in biomarkers will be estimated and compared across the study arms using Fisher's Z-transformed values.
Effect of change in red blood cell omega-3:omega-6 fatty acid ratio on within arm change in blood adiponectin
Assess correlation between change in red blood cell omega-3:omega-6 fatty acid ratio and change in blood adiponectin levels.
Effect of change in red blood cell omega-3:omega-6 fatty acid ratio on within arm change in tissue ERGI
Assess correlation between change in red blood cell omega-3:omega-6 fatty acid ratio on within arm change in tissue ERGI.
Effect of baseline bioavailable estradiol on within arm change in blood adiponectin
Assess correlation between baseline bioavailable estradiol on within arm change in blood adiponectin.
Effect of baseline and 6-month bioavailable estradiol on within arm change in tissue ERGI
Assess correlation between baseline and 6-month bioavailable estradiol on within arm change in tissue ERGI.
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