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Estradiol for ER+ Advanced Breast Cancer (ESTHER) Study

This study is testing estradiol, a type of estrogen, for women with advanced breast cancer that is estrogen receptor-positive (ER+). Researchers want to see if estradiol can benefit patients whose cancer has specific genetic changes (ESR1-mutant/amplified) more than those without these changes. You may be able to join if you are a post-menopausal woman with ER+ metastatic or recurrent breast cancer that cannot be cured, and you have already received at least one hormone-based treatment for your advanced cancer. The main goal is to see how many participants experience a clinical benefit (meaning their cancer is stable or shrinks) after 12 months of treatment. The current recruitment status is unclear.

Study design
This is an interventional study planning to enroll 36 women. It is not specified if it is randomized or blinded.
What's involved
You will receive 17b-estradiol until your disease progresses. Optional tumor biopsies and blood samples will be collected at various times.
Compensation
Not stated in the trial record.
Follow-up
After disease progression on 17b-estradiol, you may enter an optional observational phase where your progress will be tracked during your doctor's chosen treatment.

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NCT05716516

STUDY02001740;22SCH740: Estradiol For ER+ Advanced Breast Cancer (ESTHER)

Recruiting
PHASE2Ages 18+InterventionalTreatment
Dartmouth-Hitchcock Medical Center
~36 participants
Updated 2026-05-05 on ClinicalTrials.gov
What's tested:Estradiol

At a glance

Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Clinical Benefit Rate
Measured over 12 months

Conditions

Metastatic Breast Cancer

Explore related trials

Breast Carcinoma

Where it's being run

1 sites across 1 states
New Hampshire1

Study leadership

  • Muhammad Azfal, MD · PRINCIPAL_INVESTIGATOR · Dartmouth-Hitchcock Medical Center

Who to contact

Research Nurse
[email protected]
1-800-639-6918
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

Post-menopausal women with ER+ breast cancer.
Metastatic or locoregional recurrence not amenable to treatment with curative
intent.
Received ≥1 prior line of endocrine-based therapy (e.g., including tamoxifen, aromatase inhibitors, fulvestrant, or combinations) in the advanced/metastatic setting

Exclusion

During the study Treatment Phase with 17b-estradiol, no concurrent anti-cancer therapies are allowed with the following exceptions:
Exception: Trastuzumab is allowed for the treatment of subjects with a history of HER2+ disease, and will be used at the physician's discretion.
Exception: Anti-resorptive bone therapies (e.g., bisphosphonates, denosumab) are permitted.
Any investigational cancer therapy in the last 3 weeks.
Known CNS disease, unless clinically stable for ≥ 3 months.
History of any of the following:
Deep venous thrombosis.
Pulmonary embolism.
Stroke.
Acute myocardial infarction.
Congestive heart failure.
Previous malignancy not treated with curative intent, or with an estimated recurrence risk ≥30%.

What this trial measures

  • Clinical Benefit Rate12 months

    The clinical benefit rate (complete responses + partial responses + stable disease at 24 weeks) will be ascertained and compared between subjects treated with 17b-estradiol harboring amplified/mutant ESR1 and wild-type ESR1.