Estradiol + Olaparib for Breast Cancer

(PHOEBE Trial)

Overseen By Research Nurse

Age: 18+

Sex: Female

Trial Phase: Phase 1

Sponsor: Dickinson

Must not be taking: CYP3A inhibitors

Disqualifiers: CNS disease, Stroke, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: Unknown

Duration: 8 weeks for combination treatment, then until disease progression for single-agent treatment

6 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial tests a new treatment for post-menopausal women with a specific type of advanced breast cancer called ER+/HER2-. It aims to determine the safety and effectiveness of combining two drugs, olaparib and 17b-estradiol (a form of estrogen hormone therapy), for these patients. The trial seeks women whose cancer has spread and who have tried at least one hormone-based treatment. Participants will initially receive a combination of the two drugs and then continue with just one until their cancer progresses. As a Phase 1 trial, the research focuses on understanding how the treatment works in people, offering participants the opportunity to be among the first to receive this new treatment.

Will I have to stop taking my current medications?

The trial does not specify if you need to stop all current medications, but you cannot take other anti-cancer therapies or certain medications that affect liver enzymes (CYP3A inhibitors). You can continue bone therapies like bisphosphonates or denosumab.

Is there any evidence suggesting that this treatment is likely to be safe for humans?

Research has shown that olaparib is usually well-tolerated by patients. In one study, patients did not experience worsening effects even after long-term use. However, some side effects were reported. About 36.6% of patients experienced serious side effects that might require medical attention, including fatigue, low blood cell counts, and nausea.

Detailed information about using olaparib with 17b-estradiol specifically is not available. However, olaparib's approval for other types of breast cancer suggests it is considered safe for certain conditions. This trial is in its early stages, aiming to assess the safety of the combination and determine the best dose for future studies. Much remains to be learned about the safety of the two drugs used together. ^{1 2 3 4 5}

Why do researchers think this study treatment might be promising?

Researchers are excited about the combination of 17b-estradiol and Olaparib for breast cancer because it offers a new approach to treatment. Unlike traditional therapies that mainly involve chemotherapy, surgery, and radiation, this combo leverages Olaparib, a PARP inhibitor, to target cancer cells with specific genetic mutations, enhancing the effectiveness of the treatment. Additionally, the use of 17b-estradiol may help to maintain hormone balance, potentially offering a dual benefit of slowing cancer progression while managing symptoms. This innovative strategy could provide a more targeted and potentially less toxic alternative to existing options.

What evidence suggests that this treatment might be an effective treatment for breast cancer?

Research has shown that olaparib effectively treats certain types of breast cancer, helping patients live longer without their cancer worsening, particularly those with specific genetic changes like BRCA mutations. In this trial, participants will receive olaparib combined with 17b-estradiol.

Some studies suggest that 17b-estradiol might promote the growth of certain breast cancer cells, complicating its use. One study found that 42.1% of patients with advanced ER+ breast cancer responded to treatment with alternating 17b-estradiol. This trial will explore whether combining olaparib and 17b-estradiol can more effectively treat advanced ER+/HER2- breast cancer. ^{6 7 8 9 10}

Who Is on the Research Team?

Mary D. Chamberlin

Principal Investigator

Dartmouth-Hitchcock Medical Center

Are You a Good Fit for This Trial?

This trial is for post-menopausal women with a type of breast cancer that responds to hormones but not the HER2 protein. They should have advanced stages where surgery or radiation won't cure it and must have tried at least one hormone therapy before.

Inclusion Criteria

I am a post-menopausal woman with ER+ and HER2- breast cancer.

My cancer has spread or returned and cannot be cured with surgery or radiation.

I have had hormone therapy for advanced cancer.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive 2 cycles of olaparib in combination with 17b-estradiol, followed by single-agent 17b-estradiol until disease progression

8 weeks for combination treatment, then until disease progression for single-agent treatment

Follow-up

Participants are monitored for safety and effectiveness after treatment

6 months

Long-term follow-up

Progression-free survival is measured until cancer progression or death

12 months

What Are the Treatments Tested in This Trial?

Interventions

• 17b-estradiol
• Olaparib

Trial Overview The study tests the safety and optimal dose of Olaparib, a targeted cancer drug, when used with Estradiol, a form of estrogen. It's for patients with certain advanced breast cancers who've had previous treatments.

How Is the Trial Designed?

Group I: Treatment Arm Experimental Treatment 2 Interventions

Participants receive 2 cycles of olaparib in combination with 17b-estradiol and then continue to be treated with single-agent 17b-estradiol until disease progression.

17b-estradiol is already approved in European Union, United States, Canada for the following indications:

Approved in European Union as Estradiol for:

• Menopausal symptoms
• Hypoestrogenism
• Prevention of postmenopausal osteoporosis
• Breast cancer
• Advanced androgen-dependent carcinoma of the prostate

Approved in United States as Estradiol for:

• Moderate to severe vasomotor symptoms due to menopause
• Moderate to severe symptoms of vulvar and vaginal atrophy due to menopause
• Hypoestrogenism
• Prevention of postmenopausal osteoporosis
• Breast cancer
• Advanced androgen-dependent carcinoma of the prostate

Approved in Canada as Estradiol for:

• Menopausal symptoms
• Hypoestrogenism
• Prevention of postmenopausal osteoporosis
• Breast cancer
• Advanced androgen-dependent carcinoma of the prostate

Who Is Running the Clinical Trial?

Dickinson

Lead Sponsor

Trials

1

Recruited

6+

Mary D Chamberlin

Lead Sponsor

Trials

1

Recruited

6+

Gary Schwartz

Lead Sponsor

Trials

3

Recruited

30+

Dartmouth-Hitchcock Medical Center

Collaborator

Trials

548

Recruited

2,545,000+

Published Research Related to This Trial

In a study of 30 untreated prostate cancer patients, both ethinyl oestradiol combined with polyoestradiol phosphate and estramustine phosphate showed similar estrogenic effects over a 6-month follow-up period.

The treatments induced comparable changes in hormone levels, indicating that both options may be effective in managing prostate cancer through similar mechanisms.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The oestrogenic effects of ethinyl oestradiol/polyoestradiol phosphate and estramustine phosphate in patients with prostatic carcinoma. A comparative study of oestrogen sensitive liver proteins, gonadotrophins and prolactin. Daehlin, L., Damber, JE., von Schoultz, B., et al.[2019]

Polyestradiol phosphate, a slow-releasing depot estrogen, has shown good palliation and a 38% overall survival rate after five years in 105 male patients with prostatic carcinoma.

In a new study of 126 patients, combining polyestradiol phosphate with ethinylestradiol resulted in a significantly improved overall survival rate of 62%, suggesting that this combination therapy is more effective than using polyestradiol phosphate alone.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Polyestradiol phosphate and ethinyl estradiol in treatment of prostatic carcinoma. Lindstedt, E.[2015]

In a study of 21 patients with prostatic carcinoma, both ethinyl oestradiol alone and in combination with polyoestradiol phosphate significantly reduced serum testosterone and other hormone levels, but the combination treatment did not provide additional benefits.

The use of ethinyl oestradiol alone resulted in fewer complications compared to the combination treatment, with some patients experiencing serious cardiovascular and liver issues when polyoestradiol phosphate was included.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Some effects of treatment with ethinyl oestradiol with or without polyoestradiol phosphate in patients with prostatic carcinoma. Tomić, R.[2019]

In a study of 1063 pre/perimenopausal women with lymph-node-negative breast cancer, combining chemotherapy (CMF) with goserelin significantly improved disease-free survival (DFS) for those with estrogen receptor (ER)-positive tumors, especially in younger patients under 40.

The 12-year DFS was 77% for the CMF followed by goserelin group, compared to 69% for CMF alone and 68% for goserelin alone, indicating that the sequential therapy offers a beneficial long-term outcome for this patient group.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Long-term results of International Breast Cancer Study Group Trial VIII: adjuvant chemotherapy plus goserelin compared with either therapy alone for premenopausal patients with node-negative breast cancer. Karlsson, P., Sun, Z., Braun, D., et al.[2022]

Goserelin, a luteinizing hormone-releasing hormone analogue, has been shown to be at least as effective as cytotoxic chemotherapy for treating hormone receptor-positive early breast cancer in pre-/perimenopausal women, based on studies involving over 8000 patients.

Using goserelin can help avoid the side effects associated with traditional chemotherapy, providing a potentially safer treatment option for premenopausal patients with early breast cancer.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Goserelin (Zoladex)--its role in early breast cancer in pre- and perimenopausal women. Jonat, W.[2018]

A comprehensive safety review of Estratest and Estratest HS, based on over 1 million woman-years of exposure from 1989 to 1996, found no significant safety concerns, with only 863 adverse events reported, which is relatively low given the extensive use.

The most common adverse events were typical of estrogen and androgen therapies, such as weight gain and headaches, and serious adverse events were rare, indicating that these medications are safe when used as directed, with manageable risks associated with their androgen component.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Safety surveillance of esterified estrogens-methyltestosterone (Estratest and Estratest HS) replacement therapy in the United States. Phillips, E., Bauman, C.[2019]

Estetrol (E4), a new estrogen used in a combined oral contraceptive with drospirenone, has demonstrated good contraceptive efficacy and a favorable safety profile in phase 3 studies, with predictable bleeding patterns.

E4 uniquely activates nuclear estrogen receptor α (ERα) without triggering membrane ERα pathways, leading to minimal effects on breast tissue proliferation and liver function, which may reduce risks associated with traditional estrogens.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Profile of estetrol, a promising native estrogen for oral contraception and the relief of climacteric symptoms of menopause. Gérard, C., Arnal, JF., Jost, M., et al.[2022]

NOMAC-E2, an oral contraceptive containing nomegestrol acetate and estradiol, has been shown to be highly effective with a Pearl Index of less than one pregnancy per 100 woman-years, indicating a low failure rate.

The formulation is associated with a favorable bleeding pattern, fewer adverse events, and an acceptable safety profile, making it a promising option among oral contraceptives.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Nomegestrol acetate-17b-estradiol for oral contraception. Burke, A.[2021]

The study found that the estrogen 17 beta-estradiol (E2) and its metabolite 16 alpha-hydroxyestrone (16 alpha-OHE1) significantly promote the growth of estrogen receptor-positive breast cancer cells (MCF-7), with increases in colony formation of 59.4% and 105.9% respectively, indicating their potential role in tumorigenesis.

In contrast, the metabolite 2-hydroxyestrone (2-OHE1) did not promote cell growth in either in vitro or in vivo experiments, suggesting that not all E2 metabolites have the same tumor-promoting effects, and highlighting the importance of specific metabolic pathways in breast cancer progression.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

In Vitro and In Vivo Modulation of Growth Regulation in the Human Breast Cancer Cell Line MCF-7 by Estradiol Metabolites. Suto, A., Telang, NT., Tanino, H., et al.[2019]

Selective estrogen receptor modulators (SERMs) and antiestrogens, such as raloxifene and bazedoxifene, are safe options for postmenopausal women as they do not increase breast cancer risk and may even offer protection against it.

The combination of conjugated estrogens with bazedoxifene has shown an improved breast safety profile compared to traditional hormone therapies, with no increase in breast density or pain over two years, indicating a safer alternative for managing menopausal symptoms.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Selective estrogen receptor modulators and the combination therapy conjugated estrogens/bazedoxifene: A review of effects on the breast. Pickar, JH., Komm, BS.[2018]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC9676491/

17-β Estradiol up-regulates energy metabolic pathways ... 17β-estradiol (E2) decreased the Erα/Erβ ratio in ER+ breast cancer MCTS. MCF-7 cells in tridimensional culture displayed high sensitivity to E2 for growth and ...

2. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC10688025/

Alternating 17β-Estradiol and Aromatase Inhibitor ... In this single-arm study evaluating the role of alternating 17β-estradiol/AI therapy in patients with advanced ER+ breast cancer, 8/19 (42.1%) experienced CB ...

3. ascopubs.org ascopubs.org/doi/10.1200/JCO.2025.43.16_suppl.578

Use of local estrogen therapy among breast cancer ... Conclusions: The use of vaginal estrogen among this SEER-MHOS cohort of breast cancer patients showed improved survival outcomes. These findings ...

4. sciencedirect.com sciencedirect.com/science/article/pii/S0923753424048804

Review Estrogens and breast cancer Estrogen may increase breast cancer risk by inducing the progesterone receptor and augmenting progesterone signaling.

5. frontiersin.org frontiersin.org/journals/physiology/articles/10.3389/fphys.2011.00030/full

The effects of 17β-estradiol in cancer are mediated by ... 17β-estradiol (E2), the most effective female estrogen, is critical for the control of a plethora of biological responses that strongly influence several ...

6. clinicaltrials.gov clinicaltrials.gov/study/NCT05900895

Estradiol Plus Olaparib for Breast Cancer (PHOEBE) Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast ...

7. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC6503629/

OlympiAD final overall survival and tolerability results Olaparib was generally well-tolerated, with no evidence of cumulative toxicity during extended exposure. Keywords: breast cancer, germline BRCA mutation, ...

8. bigagainstbreastcancer.org bigagainstbreastcancer.org/new-data-confirms-olaparibs-survival-benefits-in-early-breast-cancer/

new data confirms olaparib's survival benefits in early ... Survival rates at six years were 87.5% for olaparib patients versus 83.2% for those on placebo. 35% Reduced risk of events: Olaparib reduced the ...

9. nejm.org nejm.org/doi/full/10.1056/NEJMoa1706450

Olaparib for Metastatic Breast Cancer in Patients with a ... The response rate was 59.9% in the olaparib group and 28.8% in the standard-therapy group. The rate of grade 3 or higher adverse events was 36.6 ...

10. ncbi.nlm.nih.gov ncbi.nlm.nih.gov/books/NBK594376/

Clinical Review - Olaparib (Lynparza) - NCBI - NIH However, olaparib could help optimize adjuvant treatment in patients with BRCA-mutated early breast cancer to improve outcomes in terms of disease recurrence ...