Randomized Double-Blind Phase II Trial of Baby Exemestane Versus Baby Tamoxifen in Post-Menopausal Women at High Risk for Breast Cancer (BabyTEARS)

Randomized Double-Blind Phase II Trial of Baby Exemestane Versus Baby Tamoxifen in Post-Menopausal Women at High Risk for Breast Cancer (BabyTEARS)

The goal of this research study is to evaluate the efficacy and safety of low-dose exemestane versus low-dose tamoxifen in post-menopausal women at high risk for breast cancer.

The names of the study drugs involved in this study are:

• Exemestane (a type of steroidal aromatase inhibitor)
• Tamoxifen (a type of selective estrogen receptor modulator)

Study Overview

• Status: Not yet recruiting
• Conditions: Breast Cancer; BRCA2 Mutation; Estrogen-receptor-positive Breast Cancer; CHEK2 Gene Mutation; Atypical Lobular Hyperplasia; Ductal Carcinoma; Ataxia Telangiectasia Mutated Gene Mutation
• Intervention / Treatment: Drug: Exemestane; Drug: Tamoxifen

Detailed Description

This randomized, double-blind, phase II trial is to evaluate the efficacy and safety of low-dose "baby" exemestane versus low-dose "baby" tamoxifen in post-menopausal women at high risk for breast cancer. Both medications are used at full doses for breast cancer treatment and to reduce breast cancer risk. Low dose tamoxifen has been shown to be effective at reducing risk with better tolerance.

Participants will be randomized into one of two study groups: Group A: Exemestane versus Group B: Tamoxifen. Randomization means a participant is placed into a study group by chance. Neither a participant or the research doctor will choose or know what group a participant is placed in. This is called a "double-blind".

The U.S. Food and Drug Administration (FDA) has not approved tamoxifen or exemestane for ER+ DCIS, High Risk Lesions, or being at high-risk for breast cancer but it has been approved for other uses.

The research study procedures include screening for eligibility, in-clinic visits, questionnaires, blood tests, Mammography scans, and bone density (DEXA) scans.

Participation in this research study is expected to last about 12 months. It is expected that about 140 people will take part in this research study. The Breast Cancer Research Foundation is supporting this research study by providing funding. MRIGlobal is providing support by supplying the study drugs.

• Study Type: Interventional
• Enrollment (Estimated): 140
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Judy Garber, MD, MPH; Phone Number: 617-632-2282; Email: judy_garber@dfciharvard.edu
• Study Contact Backup: Name: Judy Garber, MD. MPH; Phone Number: 617-582-8321; Email: judy_garber@dfciharvard.edu

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Brigham and Women's Hospital
      • Contact: Judy Garber, MD, MPH; Phone Number: 617-632-2282; Email: judy_garber@dfciharvard.edu
    • Boston, Massachusetts, United States, 02215
      • Dana Farber Cancer Institute
      • Contact: Judy Garber, MD. MPH; Phone Number: 617-632-2282; Email: judy_garber@dfciharvard.edu
      • Contact: Judy Garber, MD. MPH; Phone Number: 617-632- 2282; Email: judy_garber@dfciharvard.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Postmenopausal state is defined⁸ as no menses for 12 months without an alternative medical cause. A high follicle stimulating hormone (FSH) level in the postmenopausal range may be used to confirm a post-menopausal state in women not using hormonal contraception or hormonal replacement therapy.

• Any of the following criteria must be met:

  • Recent (within 12 months from date of consent form signature) histologic diagnosis of ER+ve (>5%) DCIS (patients with DCIS should have undergone breast-conserving therapy i.e. lumpectomy to remove the tumor with negative surgical margins followed by radiotherapy (see footnote 1 below)) diagnosis within 3 years of HRL (ADH, LCIS, ALH), or;
  • At least 3% breast cancer risk at 5 years (or 5% risk at 10yrs) per one of the following risk models: the Breast Cancer Surveillance Consortium risk calculator V3 or Tyrer-Cuzick model V8 or;
  • Known carriers of a germline pathogenic/likely pathogenetic variant in the following moderate penetrance genes (CHEK2 or ATM), or women with chest wall irradiation before age of 30 years
• Eastern Cooperative Oncology Group - Performance Status (ECOG-PS) 0-1
• Able to swallow oral medications
• Participants with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial. Specifically, all cancers diagnosed since 3 years or longer except for breast and endometrial are eligible.
• Ability to understand and the willingness to sign a written informed consent document
• Mammography performed up to 6 months before the trial consent form signature
• DEXA performed up to 12 months before the trial consent form signature
• Life expectancy ≥ 10 years
• Normal liver function tests and blood cell count
• Negative gynecological examination performed up to 6 months before the trial consent form signature.

ᶥ While DCIS and ADH are routinely excised, and treatment of DCIS often includes radiotherapy, lobular neoplasia (ALH and classic LCIS) are not routinely excised in most US centers unless radiologic-pathologic findings are discordant given the very low risk of an associated cancer.11,12 Participants with DCIS should have undergone breast-conserving therapy i.e. lumpectomy to remove the tumor with negative surgical margins followed by radiotherapy. All DCIS will require excision to clear margins per the SSO/ASCO/ASTRO margin guidelines for DCIS.88 In selected cases, the decision to omit RT might be taken according to low risk clinical-pathological factors (e.g., age>70, low grade, size < 1 cm, and genomic assays if available) as well as patient preference after full discussion of the risks and benefits.

Exclusion Criteria:

• Pre/perimenopausal women: exemestane is only effective in post-menopausal women
• History of DVT or PE: tamoxifen can increase tendency to blood clot
• Endometrial cancer: full-dose tamoxifen is associated with increased risk of endometrial cancers
• Macular disorders: tamoxifen is associated with retinal damage
• Inability to comply with study procedures: standard
• Prior use of antiestrogens within 12 months from the date of the trial consent form signature: there can be long duration effects from antiestrogens that could influence trial drug effects
• Use of hormone replacement therapy (HRT) within 3 months from the date of the trial consent form signature: similarly, wish to avoid any long lasting effect before alternate effect from study drugs
• Severe osteoporosis (T score ≤ 2.5 at either spine or hip), or recent vertebral fracture (within 6 months) not treated with zoledronic acid or denosumab: Exemestane is an aromatase inhibitor which can worsen bone loss (osteoporosis)
• Current use of terbinafine, quinidine, cinacalcet, rifampicin, phenytoin, carbamazepine, phenobarbital, St. John's wort, warfarin, erythromycin, cyclosporin, nifedipine and any concomitant coumarin-type anti-coagulant therapy: these drugs compete for the Cytochrome P450 metabolic pathways of tamoxifen and exemestane
• Moderate or severe renal impairment: Exemestane is eliminated equally by liver and renal metabolism
• Known hypersensitivity to study drugs: standard

Screening Eligibility Criteria

To register a participant to the screening phase, the following documents should be provided by the participating site:

Signed participant consent form

• Postmenopausal status, and any of the following:

  • Histological report of ER-positive DCIS within 12 months, or HRL of the breast within 3 years from date of consent form signature, or;
  • Report of risk assessment ≥3% in 5 years or 5% in 10 years of breast cancer according to the selected risk model(s) different criteria within 6 months from screening, or;
  • Documentation of women carriers of a germline pathogenic/likely pathogenetic variant in a moderate penetrance gene (CHEK2 or ATM), or;
  • Documented history of chest wall radiotherapy before age 30.
• Inclusion of Women and Minorities

Only women will be recruited in the study given that breast cancer is much more frequent in women than men and because exemestane is contraindicated in men because of risk of uncontrolled gonadal stimulation. Women of all races and ethnic groups are eligible for this trial. At participating sites, efforts will be made to enroll women from diverse ethnic and socio-economic backgrounds, including recruitment of non-white women in a selected New York city area.

NIH policy requires that women and members of minority groups and their subpopulations be included in all NIH-supported biomedical and behavioral research projects involving NIH-defined clinical research unless a clear and compelling rationale and justification establishes to the satisfaction of the funding Institute & Center (IC) Director that inclusion is inappropriate with respect to the health of the subjects or the purpose of the research. Exclusion under other circumstances designated by the Director, NIH, upon the recommendation of an IC Director based on a compelling rationale and justification. Cost is not an acceptable reason for exclusion except when the study would duplicate data from other sources. Women of childbearing potential should not be routinely excluded from participation in clinical research.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low-Dose Exemestane; Participants will be randomized 1:1 with a permuted-block technique and stratified by center and will complete: Baseline visit with assessments; Predetermined dose of Exemestane 1x on every odd day for 12 months; 3 month in-clinic visit; 6 month in-clinic visit; 9 month in-clinic visit; 12 month end of intervention in-clinic visit; Follow up for 12 months	Drug: Exemestane; A steroidal aromatase inhibitor, blinded capsules taken orally, per protocol.; Other Names: C20H24O2
Experimental: Low-Dose Tamoxifen; Participants will be randomized 1:1 with a permuted-block technique and stratified by center and will complete: Baseline visit with assessments; Predetermined dose of Tamoxifen 1x on every odd day for 12 months; 3 month in-clinic visit; 6 month in-clinic visit; 9 month in-clinic visit; 12 month end of intervention in-clinic visit; Follow up for 12 months	Drug: Tamoxifen; A selective estrogen receptor modulator, blinded capsules taken orally, per protocol.; Other Names: C32H37NO8

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in Overall Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL) Between the Two Arms at 12 Months	The MENQOL assesses the degree to which menopausal symptoms are troublesome in four domains: vasomotor (three items), sexual (three items), physical (seven items), and psychosocial (16 items). Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 to 6, where 0 indicates "not at all bothered" and 6 indicates "extremely bothered." For each participant, the difference between the baseline and 12-month overall MENQOL score will be calculated and defined as the "change."	12 Months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference of Free Estradiol Levels between Two Arms at 12 Months	Free estradiol concentration in blood will be measured to compare the hormonal effects of babyexe versus babytam.	12 Months
Difference of Estradiol/Sex Hormone Binding Globulin (SHBG) Levels between Two Arms at 12 Months	The estradiol/SHBG ratio will be calculated as total estradiol divided by SHBG to evaluate differences in hormonal effects between babyexe and babytam.	12 Months
Difference of Insulin-like Growth Factor Binding Protein 3 (IGFBP-3) Levels Between Two Arms at 12 Months	Blood levels of IGF-I will be measured to compare the effects of babyexe and babytam on IGF-I.	12 Months
Insulin-like Growth Factor I (IGF-I)/Insulin-like Growth Factor Binding Protein 3 (IGFBP-3) Ratio Between Two Arms at 12 Months	The ratio of IGF-I to IGFBP-3 in blood will be calculated to compare the effects of babyexe and babytam on IGF system balance.	12 Months
Overall Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL) at 6 Months	The MENQOL assesses the degree to which menopausal symptoms are troublesome in four domains: vasomotor (three items), sexual (three items), physical (seven items), and psychosocial (16 items). Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 to 6, where 0 indicates "not at all bothered" and 6 indicates "extremely bothered." For each participant, the difference between the baseline and 6-month overall MENQOL score will be calculated and defined as the "change."	6 months
Free Estradiol Levels	Free estradiol concentration in blood will be measured to compare the hormonal effects of babyexe versus babytam.	6 Months
Estradiol/Sex Hormone Binding Globulin (SHBG) Levels	The estradiol/SHBG ratio will be calculated as total estradiol divided by SHBG to evaluate differences in hormonal effects between babyexe and babytam.	6 months
Insulin-like Growth Factor I (IGF-I) Levels	Blood levels of IGF-I will be measured to compare the effects of babyexe and babytam on IGF-I.	6 months
Insulin-like Growth Factor Binding Protein 3 (IGFBP-3) Levels	Blood levels of IGFBP-3 will be measured to compare the effects of babyexe and babytam on IGFBP-3.	6 months
Insulin-like Growth Factor I (IGF-I)/Insulin-like Growth Factor Binding Protein 3 (IGFBP-3) Ratio	The ratio of IGF-I to IGFBP-3 in blood will be calculated to compare the effects of babyexe and babytam on IGF system balance.	6 months
Physical Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL) Between the Two Arms at 6 Months and 12 months	The MENQOL physical domain, which includes seven items, assesses the degree to which physical menopausal symptoms are troublesome. Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 ("not at all bothered") to 6 ("extremely bothered"). For each participant, the difference between the baseline and 6-month physical domain MENQOL score will be calculated and defined as the "change."	6 months and 12 months
Sexual Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL)	The MENQOL sexual domain, which includes three items, assesses the degree to which sexual menopausal symptoms are troublesome. Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 ("not at all bothered") to 6 ("extremely bothered"). For each participant, the difference between the baseline and 6-month sexual domain MENQOL score will be calculated and defined as the "change."	6 months and 12 months
Psychosocial Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL)	The MENQOL psychosocial domain, which includes sixteen items, assesses the degree to which psychosocial menopausal symptoms are troublesome. Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 ("not at all bothered") to 6 ("extremely bothered"). For each participant, the difference between the baseline and 6-month psychosocial domain MENQOL score will be calculated and defined as the "change."	6 months and 12 months
Vasomotor Domain Score Change From Baseline in Menopause-Specific Quality of Life Questionnaire (MENQOL)	The MENQOL vasomotor domain, which includes three items, assesses the degree to which vasomotor menopausal symptoms are troublesome. Each item is answered with Yes or No. If the response is Yes, the participant rates how bothersome the symptom was on a scale from 0 ("not at all bothered") to 6 ("extremely bothered"). For each participant, the difference between the baseline and 6-month vasomotor domain MENQOL score will be calculated and defined as the "change."	6 months and 12 months
Global Adverse Event (AE) Rate	Global AE rate is defined as the proportion of participants who experience any AE. AE is summarized and graded based on CTCAE v 5.0.	12 Months
Grade 2 or Higher Adverse Event (AE) Rate	Grade 2 or higher AE rate is defined as the proportion of participants who experience grade 2 or higher AE. AE is summarized and graded based on CTCAE v 5.0.	12 months
Grade 3 or Higher Adverse Event (AE) Rate	Grade 3 or higher AE rate is defined as the proportion of participants who experience grade 2 or higher AE. AE is summarized and graded based on CTCAE v 5.0.	12 months
Distribution of Maximum Adverse Event Grade per Participant	The maximum adverse event (AE) grade experienced by each participant during the treatment period will be summarized to characterize the overall toxicity profile. Adverse events will be graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. For each participant, the highest AE grade observed at any time during the treatment period will be identified, and the distribution of these maximum grades across participants will be reported, in accordance with the statistical considerations for toxicity evaluation described in Section 16.15 of the protocol.	12 months
Medication Adherence Assessed by PMAS	Medication adherence will be assessed using the PMAS instrument, as specified in Appendix H of the protocol. PMAS is a validated wording-based adherence scale and does not generate a continuous numeric summary score. Therefore, adherence will be operationalized categorically, consistent with its original validation methodology. Participants will be classified into predefined adherence categories based on their item responses (e.g., high adherence versus non-high adherence). Adherence will be summarized as the proportion of participants meeting the definition of "high adherence" within each treatment arm. Between-arm comparisons will be based on categorical distributions rather than mean or continuous scores, in accordance with Sections 9.10-9.11 of the protocol.	6 months and 12 months
BPI (Brief Pain Inventory) Score Change from Baseline	Pain will be assessed using BPI, a validated questionnaire that measures both pain intensity and the degree to which pain interferes with daily activities. Each item is scored from 0 to 10, with higher scores indicating worse pain or greater interference.	6 months and 12 months
C-Telopeptide Levels	Blood levels of C-telopeptide, a marker of bone resorption, will be measured assess changes in bone turnover.	6 months and 12 months

Collaborators and Investigators

• Sponsor: Dana-Farber Cancer Institute
• Collaborators: Breast Cancer Research Foundation
• Investigators: Principal Investigator: Judy Garber, MD. MPH, Dana-Farber Cancer Institute

Study record dates

Study Major Dates

• Study Start (Estimated): September 9, 2026
• Primary Completion (Estimated): August 31, 2027
• Study Completion (Estimated): August 31, 2028

Study Registration Dates

• First Submitted: March 24, 2026
• First Submitted That Met QC Criteria: March 24, 2026
• First Posted (Actual): March 30, 2026

Study Record Updates

• Last Update Posted (Actual): March 30, 2026
• Last Update Submitted That Met QC Criteria: March 24, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Breast Cancer; Estrogen Receptor Positive; BRCA2; Cancer Prevention; ATM; CHEK2; High Risk Breast Cancer; Ductual Carcinoma in Site; High Risk Lesions; HRL; Atypical Lobular Hyperplasia
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Neoplasms by Histologic Type; Neoplasms, Glandular and Epithelial; Adenocarcinoma; Skin Diseases; Breast Diseases; Carcinoma; Neoplasms, Ductal, Lobular, and Medullary; Skin and Connective Tissue Diseases; Breast Neoplasms; Carcinoma, Ductal; Organic Chemicals; Hydrocarbons; Hydrocarbons, Cyclic; Hydrocarbons, Aromatic; Benzene Derivatives; Stilbenes; Benzylidene Compounds; Tamoxifen; exemestane
• Other Study ID Numbers: 25-550

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The Dana-Farber / Harvard Cancer Center encourages and supports the responsible and ethical sharing of data from clinical trials. De-identified participant data from the final research dataset used in the published manuscript may only be shared under the terms of a Data Use Agreement. Requests may be directed to: [contact information for Sponsor Investigator or designee]. The protocol and statistical analysis plan will be made available on Clinicaltrials.gov only as required by federal regulation or as a condition of awards and agreements supporting the research.
• IPD Sharing Time Frame: Data can be shared no earlier than 1 year following the date of publication
• IPD Sharing Access Criteria: DFCI- Contact the Belfer office for Dana -Farber Innovations (BODFI) at innovations@dfci.harvard.edu
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No