This study will evaluate the safety and efficacy of inavolisib combination therapies in participants with untreated, PIK3CA-mutated, Stage II-III, estrogen receptor (ER)-positive, Human Epidermal Growth Factor Receptor 2 (HER2)-negative breast cancer (BC).

Inclusion Criteria:

• Histologically confirmed operable or inoperable invasive Stage II-III BC according to American Joint Committee on Cancer (AJCC) TNM staging classification
• Candidate for neoadjuvant treatment and considered appropriate for endocrine combination therapy
• Willingness to undergo breast surgery (mastectomy or breast-conserving surgery) after neoadjuvant treatment (unless inoperable)
• Documented ER-positive tumor in accordance with current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines
• Documented HER2-negative tumor in accordance with current ASCO/CAP guidelines
• Documented Ki-67 score >=5% as per local assessment
• Confirmed PIK3CA mutation

Exclusion Criteria:

• Stage IV (metastatic) BC
• Inflammatory BC (cT4d)
• Bilateral invasive BC
• History of ductal carcinoma in situ or lobular carcinoma in situ if they have received any systemic therapy for treatment or radiation therapy to the ipsilateral breast
• Previous systemic or local treatment for the primary BC currently under investigation (including excisional biopsy or any other surgery of the primary tumor and/or axillary lymph nodes, including sentinel lymph node biopsy, radiotherapy, cytotoxic, and endocrine treatments)
• Type 2 diabetes requiring ongoing systemic treatment at the time of study entry; or any history of Type 1 diabetes

For eligible studies, qualified researchers may request access to individual patient level clinical data. See Roche's commitment to transparency of clinical study information here: https://go.roche.com/data\_sharing