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Estradiol Plus Olaparib for Metastatic Breast Cancer (PHOEBE)

This study is looking at a combination of two drugs, olaparib and 17b-estradiol, for post-menopausal women with metastatic breast cancer (cancer that has spread). Your cancer must be ER+ (estrogen receptor positive) and HER2- (HER2 negative), and you must have received at least one prior hormone-based treatment for advanced breast cancer. The main goal is to find the safest and most effective dose of olaparib when given with 17b-estradiol. Researchers will measure this dose after 8 weeks. The study is currently recruiting a small number of participants to understand how well this combination works and if it can help control the cancer.

Study design
This is an interventional study with a planned enrollment of 6 women. It is designed to determine the best dose of olaparib when combined with 17b-estradiol.
What's involved
You will be treated with a combination of 17b-estradiol and olaparib for two cycles, then with single-agent 17b-estradiol until your disease progresses.
Compensation
Not stated in the trial record.
Follow-up
The primary endpoint for dose determination is measured at 8 weeks. You will continue to receive single-agent 17b-estradiol until disease progression.

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NCT05900895

Estradiol Plus Olaparib for Breast Cancer (PHOEBE)

Recruiting
PHASE1Ages 18+InterventionalTreatment
Mary D Chamberlin
~6 participants
Updated 2025-11-20 on ClinicalTrials.gov
What's tested:Olaparib17b-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
Determine the Phase II dose of olaparib in combination with 17b-estradiol
Measured over 8 weeks

Conditions

Metastatic Breast Cancer

Explore related trials

Breast Carcinoma

Where it's being run

1 sites across 1 states
New Hampshire1

Study leadership

  • Mary Chamberlin, 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+/HER2- breast cancer.
Metastatic or locoregional recurrence not amenable to treatment with curative intent.
Received ≥1 prior line of endocrine-based therapy in the advanced/metastatic setting.

Exclusion

During study treatment, no concurrent anti-cancer therapies are allowed with the following exceptions:
Any investigational cancer therapy or systemic chemotherapy in the last 3 weeks.
Any radiation therapy in the last 2 weeks.
Known CNS disease, unless clinically stable for ≥ 3 months.
Concomitant use of known strong or moderate CYP3A inhibitors.
Persistent toxicities (≥CTCAE grade 2) caused by previous cancer therapy.
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%
Severe renal impairment (creatinine clearance ≤ 30 mL/min).

What this trial measures

  • Determine the Phase II dose of olaparib in combination with 17b-estradiol8 weeks

    Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer.