Clinical trials · California
ER Positive Breast Cancer clinical trials in California
We’re tracking 54 recruiting er positive breast cancer studies with a site in California — including Phase 1, Phase 1/Phase 2, Phase 2 and Phase 3 studies, each written for real people, not researchers.
Recruiting studies in California
- NCT06590857RecruitingPhase 1/Phase 2
Study of targeted radiation for advanced breast cancer
This trial tests a new type of radiation therapy that targets a specific protein on some breast cancer cells. It may help people whose cancer has stopped responding to other treatments.
Irvine, CaliforniaAges Any age - NCT07647328RecruitingPhase 3
Camizestrant and ribociclib for advanced hormone-receptor-positive breast cancer
This trial tests a combination of two drugs (camizestrant and ribociclib) for advanced breast cancer that is hormone-receptor-positive and HER2-negative. The study aims to see if this combination helps patients whose cancer cannot be surgically removed or treated with radiation alone.
Palo Alto, CaliforniaAges 18–130 - NCT07541079RecruitingPhase 3
Testing a New Breast Cancer Drug for Women Who Can't Tolerate Current Therapy
This study tests giredestrant, a new hormone-blocking medication, in postmenopausal women with early-stage ER+ breast cancer who have experienced intolerable side effects from their current aromatase inhibitor therapy. The trial will measure how well you tolerate this new drug and how it affects your quality of life.
Fountain Valley, CaliforniaAges 18 years+ - NCT07405801RecruitingPhase 2
Inavolisib plus ribociclib plus fulvestrant for advanced breast cancer
This trial tests a combination of three drugs (inavolisib, ribociclib, and fulvestrant) compared to a placebo plus two of the drugs (ribociclib and fulvestrant) for people with advanced hormone receptor-positive breast cancer who have not had prior treatment for advanced disease. The goal is to see if adding inavolisib improves outcomes.
Anaheim, CaliforniaAges 18 years+ - NCT07391774RecruitingPhase 3
Hormone therapy with or without chemo for early breast cancer
This trial tests whether skipping chemotherapy and using only hormone therapy with a drug called ribociclib works as well as chemotherapy followed by hormone therapy with ribociclib for certain early breast cancers that have a low risk of coming back.
Auburn, CaliforniaAges 18 years+ - NCT07214532Recruiting
Using a blood test to guide breast cancer therapy
This study tests whether a blood test can help decide when to start additional hormone-blocking therapy for early-stage breast cancer. It aims to see if starting therapy only when the test detects cancer DNA is as effective as giving it to everyone.
Loma Linda, CaliforniaAges 18 years+ - NCT07191717RecruitingPhase 2
Imlunestrant and abemaciclib for early ER+ breast cancer
This trial tests whether adding two targeted drugs, imlunestrant and abemaciclib, to your usual hormone therapy can lower the chance of your breast cancer coming back. It is for people with early-stage ER+ breast cancer who have no signs of cancer on scans but have tiny amounts of tumor DNA in their blood (called ctDNA).
Los Angeles, CaliforniaAges 18 years+ - NCT07100106RecruitingPhase 1/Phase 2
Study of GDC-4198 alone or with giredestrant for advanced breast cancer
This trial tests a new treatment (GDC-4198) alone or with another drug (giredestrant) compared to a standard combination (abemaciclib and giredestrant) for people with advanced hormone receptor-positive, HER2-negative breast cancer that has progressed after previous treatments.
Duarte, CaliforniaAges 18 years+ - NCT07085767RecruitingPhase 3
Palazestrant and ribociclib for first-line advanced breast cancer
This trial tests a new drug (palazestrant) combined with ribociclib for people with a common type of advanced breast cancer that is estrogen receptor-positive and HER2-negative. You may qualify if you haven't had treatment for advanced disease and your cancer has either just been found or came back long after completing hormone therapy.
Beverly Hills, CaliforniaAges 18 years+ - NCT07054190RecruitingPhase 2
Testing inavolisib for early-stage PIK3CA-mutated breast cancer
This study tests a new drug called inavolisib for people with early-stage breast cancer that has a specific genetic change (PIK3CA mutation). The goal is to see if adding this drug to standard hormone therapy is safe and effective before surgery.
Los Angeles, CaliforniaAges 18 years+ - NCT06896474Recruiting
Breast cancer treatment choice help for women 70 and older
This study tests a decision aid to help women 70 and older with early stage breast cancer choose their treatment. It looks at whether the tool helps patients and their doctors make a confident treatment choice.
Los Angeles, CaliforniaAges 18 years+ - NCT06876714RecruitingPhase 3
Shorter vs Longer HER2 Therapy for Breast Cancer with Complete Response
This trial compares 6 months versus 12 months of HER2-targeted therapy for people with HER2+ breast cancer who had a complete response after chemo and trastuzumab. The goal is to see if a shorter treatment is just as effective.
Arroyo Grande, CaliforniaAges 18 years+ - NCT06790693RecruitingPhase 3
Inavolisib plus hormone therapy for advanced breast cancer
This trial tests a new targeted therapy, inavolisib, combined with standard hormone therapy and a CDK4/6 inhibitor for people with a specific genetic mutation (PIK3CA) in their hormone receptor-positive, HER2-negative advanced breast cancer that has not been treated before. It compares this combination to a placebo plus the same standard treatments.
Burbank, CaliforniaAges 18 years+ - NCT06551116Recruiting
Better HER2 testing for HER2-low breast cancer on Enhertu
This study looks at using a more detailed lab test to measure HER2 levels in people with HER2-low metastatic breast cancer who are starting or have just started treatment with Enhertu. The goal is to see if this test can help doctors better understand who might benefit from Enhertu.
San Francisco, CaliforniaAges 18 years+ - NCT06533826RecruitingPhase 2
Testing two antibody drugs for HER2-low breast cancer
This trial tests two antibody-drug conjugates (Enhertu and Datroway) for breast cancer that is HER2-low or HER2-0. It aims to find the best treatment sequence for people whose cancer has stopped responding to prior therapy.
San Francisco, CaliforniaAges 18 years+ - NCT06492616RecruitingPhase 3
Elacestrant versus standard hormone therapy for early breast cancer
This trial compares a new medicine, elacestrant, to the usual hormone therapy for people with early-stage breast cancer that is hormone receptor-positive and HER2-negative, and who have a high chance of it coming back. The goal is to see if elacestrant works better at preventing the cancer from returning.
Bakersfield, CaliforniaAges 18 years+ - NCT06445738Recruiting
Can some women safely skip radiation after breast cancer surgery?
This trial is for women 50 and older with early-stage, hormone-positive or HER2-positive breast cancer. It tests whether it is safe to skip radiation therapy after a lumpectomy if an MRI before surgery shows the breast tissue looks a certain way.
San Francisco, CaliforniaAges 50 years+ - NCT06260033RecruitingPhase 2
Radiation Therapy for Oligoprogressive ER+ Breast Cancer
This trial tests whether a precise radiation treatment (SBRT) can target a few growing spots of estrogen receptor-positive breast cancer that has spread to other parts of the body. It also uses a special PET scan (FES PET/CT) to see how well the cancer responds. The goal is to slow down the cancer and delay the need for stronger treatments.
Duarte, CaliforniaAges 18 years+ - NCT06224673RecruitingPhase 2
Testing ARX788 for HER2-low advanced breast cancer
This trial tests a new drug, ARX788, for people with HER2-low breast cancer that has spread or cannot be removed by surgery. The goal is to see if ARX788 helps shrink or control the cancer.
San Francisco, CaliforniaAges 18 years+ - NCT06099769RecruitingPhase 2
Testing enzalutamide with or without mifepristone for AR-positive breast cancer
This trial tests if adding the drug mifepristone to the standard antiandrogen enzalutamide works better than enzalutamide alone or chemotherapy for people with a specific type of breast cancer that has androgen receptors. It aims to find a new targeted treatment option for triple-negative or ER-low breast cancer.
San Francisco, CaliforniaAges 18 years+ - NCT05929768RecruitingPhase 3
Shorter chemo plus immunotherapy without anthracyclines for early TNBC
This Phase 3 trial tests whether a shorter course of chemotherapy plus immunotherapy can work as well as standard treatment for early-stage triple-negative breast cancer. It avoids anthracycline drugs and may help reduce exposure to those medicines if the shorter plan is effective and safe.
Walnut Creek, CaliforniaAges 18 years+ - NCT06058377RecruitingPhase 3
Adding immunotherapy to chemo for stage II-III breast cancer
This trial tests whether adding the immunotherapy drug durvalumab to standard chemotherapy works better than chemo alone for people with hormone receptor positive, HER2 negative breast cancer that is stage II or III and has a high-risk genetic score (MammaPrint High Risk 2).
Auburn, CaliforniaAges 18 years+ - NCT06072612RecruitingPhase 3
Bria-IMT plus CPI vs standard care for advanced breast cancer
This trial tests a new combination of two immunotherapy drugs (Bria-IMT and a checkpoint inhibitor) against your doctor's choice of standard treatments. It is for people with advanced breast cancer that has spread and who have already tried several prior therapies.
Anaheim, CaliforniaAges 18 years+ - NCT05989828RecruitingPhase 1
Engineered immune cells for advanced triple-negative breast cancer
This trial tests a personalized treatment where your own immune cells are modified to recognize and attack cancer cells that have a specific marker called NY-ESO-1. It is for people with triple-negative breast cancer that has not responded to at least two prior treatments.
Los Angeles, CaliforniaAges 18 years+
Where these studies are running in California
Institutions with a site for the recruiting er positive breast cancer studies listed above.
- City of Hope · 6 studies
- Cedars-Sinai Cancer - Tarzana · 4 studies
- City of Hope at Irvine Lennar · 4 studies
- Huntington Memorial Hospital · 4 studies
- Palo Alto Medical Foundation · 4 studies
- Tower Cancer Research Foundation · 4 studies
- Alta Bates Summit Medical Center-Herrick Campus · 3 studies
- California Pacific Medical Center · 3 studies
What taking part in a er positive breast cancer study involves
A screening visit first
Before anything else, the study team checks whether you fit — usually a visit with some tests. You can stop at any point, and screening is typically free.
Care at a nearby site
Study visits happen at a clinic or hospital taking part. Many studies cover the cost of the study treatment and related visits, and some reimburse travel.
You stay in control
Taking part is voluntary and you can leave a study at any time, for any reason, without affecting your regular care.
The team decides eligibility
Our fit check is a helpful first read, not a decision. The study team makes the final call after reviewing your health history.
ER Positive Breast Cancer trials in other states
Common questions
- Are there er positive breast cancer clinical trials in California?
- Yes. We're currently tracking 54 recruiting er positive breast cancer studies with a site in California, each rewritten in plain language so you can see what it's testing and who it's for.
- How do I find out if I qualify for a er positive breast cancer study in California?
- Each study lists its eligibility rules — age, diagnosis, prior treatments. On every trial page we explain these in plain language and offer a short, optional pre-screen for a fit read. The study team makes the final decision.
- Do I have to live in California to take part?
- Not necessarily. These studies have a site in California, but eligibility is about your health, not your address — some people travel to take part, and a few studies reimburse travel. The study team can tell you what's required.
- Does it cost anything to join a er positive breast cancer trial?
- Using Clin2 is always free. Many trials cover the study treatment and related visits; some reimburse travel. The study team explains exactly what's covered before you decide.
Not the right time?
New er positive breast cancer studies open in California regularly. Set up a health profile and we’ll quietly watch for studies that fit you and email you when one opens.
Clin2 helps you find and understand clinical trials and does not provide medical advice. Study data comes from ClinicalTrials.gov. Talk with your doctor about whether a specific trial is right for you.