Clinical trials · California
ER Positive Breast Cancer clinical trials in California
We’re tracking 55 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
- 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.
Greenbrae, CaliforniaAges 18 years+ - NCT04768426RecruitingPhase 2
Watching DNA in blood while taking capecitabine after breast cancer
This trial checks how a blood test that looks for cancer DNA (ctDNA) changes during and after you take capecitabine after early triple-negative breast cancer. It aims to see whether these blood test results can help monitor the chance of the cancer coming back.
Stanford, CaliforniaAges 18 years+ - NCT05304962RecruitingPhase 1
Test drug RGT-419B for advanced ER+ HER2- breast cancer
This Phase 1 study tests a new drug (RGT-419B), given alone or with hormone (endocrine) therapy, in people with advanced ER-positive, HER2-negative breast cancer that has progressed after standard treatments. It looks mainly at safety and early signs of how well the treatment may work.
La Jolla, 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+ - 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+ - 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.
Duarte, CaliforniaAges 18–130 - 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+ - NCT03723928Recruiting
Blood test–guided monitoring for metastatic breast cancer treatment
This study checks whether specific blood “tumor marker” levels can help monitor how hormone receptor–positive, HER2-negative metastatic breast cancer responds to first-line therapy. It uses regular blood tests (and sometimes scans) to see if this marker-based monitoring is useful and reliable.
Irvine, 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+ - NCT06065748RecruitingPhase 3
New hormone therapy for advanced breast cancer after prior treatment
This trial tests a new oral hormone therapy, giredestrant, against a standard hormone therapy (fulvestrant) when both are given with a CDK4/6 inhibitor. It is for people with advanced ER-positive, HER2-negative breast cancer that has come back after initial hormone therapy, and who have not yet had other treatments for advanced disease.
Auburn, CaliforniaAges 18 years+ - NCT05812807RecruitingPhase 3
Pembrolizumab versus monitoring after triple-negative breast cancer response
This trial checks whether giving pembrolizumab (an immunotherapy) after surgery helps people with triple-negative breast cancer reduce the chance of the cancer coming back, compared with close monitoring only. It’s for patients who had no remaining invasive cancer after neoadjuvant chemotherapy plus pembrolizumab.
Arroyo Grande, 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+ - 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.
Berkeley, 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+ - NCT05879926RecruitingPhase 3
Testing chemo after hormone therapy in premenopausal early breast cancer
This Phase 3 trial checks whether adding chemotherapy after standard hormone-blocking treatment works better for some premenopausal women with early-stage, ER-positive, HER2-negative breast cancer. It targets patients with limited lymph node spread and a lower-to-intermediate tumor “recurrence” risk score.
Anaheim, CaliforniaAges 18–60 - 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+ - 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+ - NCT03606967RecruitingPhase 2
Individualized vaccine added to standard treatment for metastatic triple-negative breast cancer
This Phase 2 trial tests whether adding a personalized cancer vaccine to durvalumab (an immunotherapy), tremelimumab (another immunotherapy), and chemotherapy can improve outcomes for people with metastatic triple-negative breast cancer. It may help your immune system recognize your specific tumor features.
Orange, CaliforniaAges 18 years+ - NCT04434040RecruitingPhase 2
Atezolizumab and sacituzumab to prevent breast cancer return
This trial tests two medicines after surgery and chemotherapy to help lower the risk that triple-negative breast cancer comes back. It’s for people whose cancer still showed “residual” invasive disease after neoadjuvant (before-surgery) chemotherapy, and whose blood test shows traces of tumor DNA.
San Francisco, CaliforniaAges 18 years+ - NCT04802759RecruitingPhase 1/Phase 2
Testing drug combinations for recurrent or advanced ER-positive breast cancer
This early-phase trial tests several combinations of cancer medicines to slow or control ER-positive breast cancer that has returned or progressed. It also checks safety and whether tumor or blood biomarkers can help match the right treatment to the right person.
Duarte, CaliforniaAges 18 years+ - NCT04893109RecruitingPhase 2
Study compares two HER2 breast cancer treatments after surgery
This Phase 2 study tests two different medicines given after breast surgery to reduce the risk of cancer coming back. It is only for people with early-stage HER2-positive breast cancer with limited or no lymph node spread.
San Francisco, CaliforniaAges 18 years+ - NCT05386108RecruitingPhase 1/Phase 2
Test abemaciclib plus elacestrant for breast cancer brain spread
This trial studies whether the combination of abemaciclib and elacestrant can slow or shrink ER-positive, HER2-negative breast cancer that has spread to the brain. It is designed for people whose cancer has progressed despite prior hormone (endocrine) treatment.
Fullerton, CaliforniaAges 18 years+ - NCT05491226RecruitingPhase 2
Pembrolizumab plus radiation and myeloid-targeting for high-risk breast cancer
This trial studies whether adding pembrolizumab (an immune “unlocking” drug) to radiation and another treatment that targets certain immune cells can improve outcomes for women with high-risk, early-stage triple negative breast cancer. You may be considered if your cancer has signs that it may respond less to immunotherapy on its own.
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.
- Cedars-Sinai Cancer - Tarzana · 6 studies
- City of Hope Orange County Lennar Foundation Cancer Center · 6 studies
- Sutter Medical Center Sacramento · 6 studies
- Tower Hematology Oncology Medical Group · 6 studies
- University of California, Irvine Medical Center / UC Irvine Health · 6 studies
- Alta Bates Summit Medical Center · 5 studies
- Cedars-Sinai Medical Center · 5 studies
- City of Hope Comprehensive Cancer Center · 5 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 55 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.