The goal of this trial is to see if active surveillance monitoring and hormonal therapy in patients diagnosed with ductal cell carcinoma in situ (DCIS), an early stage of breast cancer, can be an effective management of the disease.

Participants will be asked to receive control hormonal therapy or an investigational hormonal therapy treatment. Participants will be asked to return for evaluation with MRI at three months and six months. Depending on the evaluation participants will have the option to continue on the treatment. If the evaluation suggests surgery is recommended, the participant will discontinue the study treatment and will undergo surgery. In addition to the treatment and MRI evaluation, participants will be asked to provide blood sample to understand their immune status, provide saliva sample for genetic testing, provide the study with a portion of the tissue or slides generated from tissue removed during surgery performed as part of their standard of care.

The purpose of this study is to assess the safety of GDC-4198 alone and in combination with giredestrant and also the efficacy of GDC-4198 + giredestrant versus abemaciclib + giredestrant in participants with locally advanced or metastatic ER+, HER2- breast cancer. The study consists of 2 phases: Phase Ib and Phase II. Phase Ib will evaluate the safety and pharmacokinetics (PK) of GDC-4198 alone and in combination with giredestrant. Phase II stage will compare the activity and safety of GDC-4198 and giredestrant with abemaciclib and giredestrant.

Participants from Study RGT-419B\_01-101 (NCT05304962) who are experiencing clinical benefit with GDC-4198, as determined by the investigator, may enroll in this study and continue receiving GDC-4198 at their current dose level following closure of Study RGT-419B\_01-101.

The purpose of this study is to investigate the efficacy and safety of BGB-43395 in combination with letrozole compared with investigator's choice of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) in combination with letrozole in patients with advanced or metastatic hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer (BC) who have not received prior systemic treatment for advanced or metastatic disease.

The purpose of this study is to learn about the safety and effects of the study medicine PF-07248144 when given along with fulvestrant for the possible treatment of HR-positive, HER2-negative advanced or metastatic breast cancer.

HR-positive breast cancer cells have proteins on their surface called receptors that bind to hormones like estrogen and progesterone (female sex hormones). These hormones can promote the growth of cancer cells.

HER2-negative describes cells that have a small amount or none of a protein called HER2 on their surface. In normal cells, HER2 helps control cell growth. Cancer cells that are HER2-negative may grow more slowly and are less likely to recur (come back) or spread to other parts of the body than cancer cells that have a large amount of HER2 on their surface.

Advanced cancer is a term that is often used to describe cancer that is unlikely to be cured.

Metastatic cancer is the type where the cancer cells spread from one part of the body to another.

This study is seeking for participants whose breast cancer has gotten worsen after receiving cyclin dependent kinase (CDK) 4/6 inhibitor-based therapy.

Half of participants in this study will receive their usual study treatment, everolimus with endocrine therapy (either exemestane or fulvestrant) for HR-positive/HER2-negative advanced or metastatic breast cancer (A/mBC). The study doctor will discuss which hormone therapy is right for the participant before treatment begins.

PF-07248144 is a tablet that will be taken by mouth at home every day in a 28-day cycle. Fulvestrant will be given as two injections (one injection in the buttock) at visits to the study clinic. Everolimus and exemestane are also tablets and will be taken by mouth at home every day in a 28-day cycle.

The study will compare the experiences of people receiving PF-07248144 in combination with fulvestrant to those of the people who do not. This will help see if PF-07248144 in combination with fulvestrant is safe and effective.

This is an umbrella study evaluating the efficacy and safety of multiple treatment combinations in participants with metastatic or inoperable locally advanced breast cancer.

The study will be performed in two stages. During Stage 1, seven cohorts will be enrolled in parallel in this study:

Cohort 1 will consist of programmed death-ligand 1 (PD-L1)-positive participants who have received no prior systemic therapy for metastatic or inoperable locally advanced triple-negative breast cancer (TNBC) (first-line \[1L\] PD-L1+ cohort).

Cohort 2 will consist of participants who had disease progression during or following 1L treatment with chemotherapy for metastatic or inoperable locally-advanced TNBC and have not received cancer immunotherapy (CIT) (second-line \[2L\] CIT-nave cohort).

Cohort 3, 5, 6 and 7 will consist of participants with locally advanced or metastatic hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative disease with one or more PIK3CA mutations.

Cohort 4 will consist of participants with locally advanced or metastatic HER2+ /HER2-low disease with one or more PIK3CA mutations who had disease progression on standard-of-care therapies (HER2+ /HER2-low cohort).

In each cohort, eligible participants will initially be assigned to one of several treatment arms (Stage 1). During Stage 2, participants in the 2L CIT-nave cohort who experience disease progression, loss of clinical benefit, or unacceptable toxicity during Stage 1 may be eligible to continue treatment with a different treatment combination, provided Stage 2 is open for enrollment and all eligibility criteria are met.

This is an open-label, multicenter, two-arm Phase II clinical trial that will evaluate the impact of 2nd line chemotherapy (i.e. capecitabine) on survival in patients with non-Luminal A hormone receptor-positive (HR+) metastatic breast cancer (MBC)

This research study is looking to see how well male breast cancer responds to preoperative treatment with endocrine therapy and which endocrine therapy regimen is the most effective treatment for male breast cancer.

The drugs used in this study are:

* Tamoxifen
* Anastrozole
* Degarelix
* Abemaciclib