REFINING TAMOXIFEN DOSE FOR PREMENOPAUSAL BREAST CANCER RISK REDUCTION (RENAISSANCE): A PHASE II SINGLE ARM TRIAL

Eligibility: Inclusion Criteria
  •   * Premenopausal women at the time of enrollment defined by any of the following:
    •   * Age under 50 years and regular menstruation (most recent period within the past 3 months)
    •   * Age under 50 years and continuous hormonal contraception use and at least one intact ovary
    •   * Women who are not postmenopausal based on serum hormone levels (estradiol = 30 pg/mL, follicle-stimulating hormone [FSH] >= 30 IU/mL)
  •   * Women with any of the following:
    •   * A history of unilateral estrogen receptor (ER) positive ductal carcinoma in situ (DCIS) with local therapy completed (as determined by treating physician recommendation and patient acceptance) at least 1 month prior to study entry. (The untreated breast will be the study breast, for both imaging and optional biopsy)
    •   * Recent or prior lobular carcinoma in situ (LCIS), or any form of epithelial atypia
    •   * Are risk eligible for preventive medication based on a five-year risk of 1.7% or greater, estimated with a validated model: the National Cancer Institute (NCI) Breast Cancer Risk Assessment Tool, Tyrer-Cusick, Breast Cancer Surveillance Consortium
    •   * Are tamoxifen-eligible by American Society of Clinical Oncology (ASCO) guidelines (>= 2-fold increased risk compared to peer if age >= 45 years, and >= 4-fold increased risk if age 45 years)
    •   * A history of mantle radiotherapy
    •   * A moderate penetrance germline pathogenic variant
  •   * Participants >= 18 and = 55 years old will be enrolled. Our trial objectives are not relevant to females under 18 years of age since breast cancer is extraordinarily rare in this age group, and there are no guidelines regarding use of tamoxifen in children, even if know to be at very high risk for breast cancer when older. Because no dosing or adverse event (AE) data are currently available on the use of tamoxifen in participants 18 years of age
  •   * Eastern Cooperative Oncology Group (ECOG) performance status must be = 2 (Karnofsky >= 60%)
  •   * Human immunodeficiency virus (HIV)-infected patients are eligible to participate if they are on effective anti-retroviral therapy with undetectable viral load within the prior 6 months
  •   * Women with evidence of chronic hepatitis B virus (HBV) infection, are also eligible if the HBV viral load is undetectable; they may be on suppressive therapy, if indicated
  •   * Women with a history of hepatitis C virus (HCV) infection are eligible if treated and cured. For those who are currently on treatment, they are eligible if they have an undetectable HCV viral load
  •   * Women with herpes simplex virus (HSV) infection are eligible if on chronic or as needed (due to a flare) suppressive antiviral therapy
  •   * Hormonal contraceptive users are eligible and should maintain the same oral contraceptive preparation throughout the duration of the trial. For women who have a levonorgestrel-coated intra-uterine device, removal for medical reasons will be allowed
  •   * The effects of tamoxifen on the developing human fetus at the recommended therapeutic dose are unknown. For this reason and because tamoxifen is known to be teratogenic, women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her study physician immediately
  •   * Ability to understand and the willingness to sign a written informed consent document
Exclusion Criteria
  •   * Breast Imaging Reporting and Data System (BIRADS) breast density category A on most recent mammogram
  •   * History of selective estrogen receptor modulator (SERM) use within the past 5 years unless:
    •   * Use was less than 6 months duration in the past 5 years and not used in the 1 year prior to enrollment OR
    •   * Use was no greater than 2 months duration in the past 1 year and not used in the 6 months prior to enrollment
  •   * History of invasive breast cancer
  •   * Prior bilateral breast surgery (mastectomy or breast augmentation surgery including breast implants)
  •   * Women with "mosaic mammographic screening views", i.e., whose larger breast size precludes being imaged within a single mammographic screening view
  •   * Current use of a strong CYP3A4 inducer or a strong CYP2D6 inhibitor unless willing and able to discontinue use and switch to an alternative medication for the duration of participation, under the advice of their physician. If the physician believes the current medication is medically necessary, the participant will not be eligible
  •   * Current use of Warfarin
  •   * Planning to become pregnant within the next two years. Potential study participants will be questioned about this and excluded if they are planning pregnancy over the next 20 months
  •   * History of thromboembolism. A history of superficial thrombophlebitis is allowed
  •   * History of uterine cancer or atypical uterine hyperplasia with uterus intact
  •   * Participants may not be receiving any other investigational agents
  •   * History of allergic reactions attributed to compounds of similar chemical or biologic composition to tamoxifen
  •   * Uncontrolled intercurrent illness or psychiatric illness/social situations that would limit compliance with study requirements
  •   * Pregnant women are excluded from this study because tamoxifen a category D agent with the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk for AEs in nursing infants secondary to treatment of the mother with tamoxifen. Breastfeeding should be discontinued if the mother is treated with tamoxifen