Old hormone, new hope: estradiol trial targets tough breast cancers
NCT ID NCT05716516
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This phase 2 study tests estradiol, a form of estrogen, in postmenopausal women with advanced ER+ breast cancer that has stopped responding to other hormone therapies. The goal is to see if patients with a specific genetic change (ESR1 mutation) benefit more than those without it. The trial enrolls 36 participants and measures tumor shrinkage and disease control at 24 weeks.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Estradiol (a form of estrogen hormone)
- What this could lead to
- If successful, this could show that estradiol therapy benefits certain patients with advanced breast cancer who have specific genetic changes.
- What could go wrong
- This is a small early-phase trial with only 36 participants, so results may not apply broadly. Estradiol can cause side effects like blood clots or hormone-related symptoms.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 2
Tests whether the treatment actually works, and watches for side effects, in a larger group.
- Participants
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About 36 people
The number the study aims to enrol. It can still change while the study runs.
- Started
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May 2023
- Expected to finish
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May 2027
An estimate. End dates often move.
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 years and older
- Sex
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Female participants only
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
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Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * 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 Criteria: * 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%.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
How to take part
Only the study team decides who joins. These are the ways to reach them.
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The places running it
1 site. The list below names each one and where it is.
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The official record
ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.
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A doctor treating you
A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.
Contacts and locations
Locations
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Dartmouth-Hitchcock Medical Center
RECRUITINGLebanon, New Hampshire, 03756, United States
More trials for these conditions
Other studies related to the condition(s) this trial covers.
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- New antibody aims to preserve immune checkpoint while fighting cancer
- Zapping a few growing tumors may keep breast cancer drugs working longer
- Can a Two-Drug combo outsmart resistant breast and ovarian cancers?
- Can a platform trial match the right drug combo to each tumor?
- Can a vaccine teach the immune system to fight HER2-Positive tumors?