Low Dose Tamoxifen With or Without Omega-3 Fatty Acids for Breast Cancer Risk Reduction

Recruiting now · Phase 2

Conditions studied: Breast Atypical Hyperplasia, Breast Carcinoma, Breast Ductal Carcinoma In Situ, Breast Lobular Carcinoma In Situ

In brief

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.

Key facts

Study ID

NCT06195306

Run by

National Cancer Institute (NCI)

People needed

66

Starts

2025-07-28

Expected to finish

2028-01-01

Last updated by the study team

2026-08-04

Who can join

Age: 45 and older, up to 74. Sex: female. Healthy volunteers: accepted.

You may qualify if…

• 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
• Amenorrhea for greater than 2 months with serum follicle-stimulating hormone (FSH) in postmenopausal range (>= 25 IU/L). Women with ovaries and a prior hysterectomy or endometrial ablation < age 55 must have a FSH >= 25 IU/L. Women may be on vaginal low dose estrogen preparations for vaginal dryness. Women over age 50 with a levonorgestrel intrauterine device in place for 2 or more years and not planning removal in the next 6 month are also eligible if FSH >= 25 IU/L
• Note: FSH will be done at time of screening
• Women with intact ovaries and uterus < age 55 must have a negative pregnancy test prior to randomization
• Overweight or obese (body mass index [BMI] >= 25 kg/m\^2)
• Note: BMI must be calculated within 28 days of randomization
• Willing to undergo a fasting blood draw and non-fasting RPFNA with fixed and frozen aliquots sent to University of Kansas Medical Center (KUMC)
• At increased risk of breast cancer per at least one of the following:
• Personal medical history
• History of atypical hyperplasia or lobular carcinoma in situ (LCIS) found on breast biopsy
• History of unilateral ductal carcinoma in situ treated with unilateral mastectomy, lumpectomy, or local excision with or without radiation and this treatment was completed at least 3 months prior to the screening RPFNA
• High mammographic density determined by one of the following:
• Visual estimate of area of density (VAS) > 50%,
• Volpara (trademark) >= 15% dense volume (Volpara d)
• Breast Imaging Reporting and Data System (BIRADS) assessment = extremely dense (BIRADs D)
• Genetic test result
• Germline gene mutation in ATM, BARD1, BRCA2, CDH1, CHEK2, NF1, PALB2, PTEN, RAD51C, RAD51D, or STK11
• Polygenic lifetime risk score >= 2x average or 25%
• Calculated risk based on standard models
• Five-year Breast Cancer Risk Assessment Tool (BCRAT) (version 2.0) >= 1.66%
• Ten-year International Breast Cancer Intervention Study risk evaluation tool (IBIS) (version 8) >= 3%
• Ten-year relative risk IBIS (version 8) >= 2X that for age group

You may not qualify if…

• Exclusions based on current or past conditions:
• 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
• Currently breastfeeding (concern that tamoxifen may be in breast milk) or nursing within past 12 months (concern about milk fistula with RPFNA)
• Type I or type II diabetes mellitus requiring current pharmacologic treatment (including metformin, glucagon-like peptide 1 agonists, insulin, sulfonylurea)
• Prior deep vein thrombosis, pulmonary embolus, or stroke
• Prior gastric bypass surgery
• History of chronic liver disease including NASH (nonalcoholic steatohepatitis) or cirrhosis
• Pathogenic or likely pathogenic germline mutation in BRCA1 or TP53
• Exclusions based on medications:
• Current use of prescription anticoagulants such as Coumadin (warfarin), direct-acting oral anticoagulants such as Xarelto (rivaroxaban) or Eliquis (apixaban) or heparin
• Women who would not be able to or do not wish to discontinue daily use of aspirin (81mg or higher) and aspirin containing products (81 mg or higher) at least 3 weeks prior to each RPFNA
• Note: Women may resume daily use of aspirin and aspirin containing products 3 days after each RPFNA procedure
• Current use of a levonorgestrel intrauterine device if in place less than 2 years or if there is planned removal within the next 6 months
• Current use of hormone therapy (oral, transdermal, or injectable)
• Note: Vaginal estrogen is allowed
• Prior treatment with tamoxifen, aromatase inhibitor or selective estrogen receptor degrader for more than 2 months
• Note: Women with < 2 months of these drugs must be off for at least 6 months before they may begin biomarker screening tests
• Greater than 1 gram daily of omega-3 fatty acid supplement within the last 6 months
• Current use of prescription immunosuppressive drugs
• Current use of CYP3A4 strong inducers rifampin or aminoglutethimide
• Current use of or plans to initiate a glucagon-like peptide 1 agonist within the next 6 months
• Current use of metformin for any indication

Where it is running

• University of Kansas Cancer Center — Kansas City, Kansas, United States (enrolling)
• University of Michigan Rogel Cancer Center — Ann Arbor, Michigan, United States (enrolling)
• Ohio State University Comprehensive Cancer Center — Columbus, Ohio, United States (enrolling)

Full record on ClinicalTrials.gov

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