Alpelisib (BYL719) in Combination With Continued Endocrine Therapy Following Progression on Endocrine Therapy in Hormone Receptor Positive, HER2 Negative, PIK3CA Mutant Metastatic Breast Cancer

Patients who have histologically confirmed metastatic or unresectable (not amenable to curative therapy) breast cancer may be screened for eligibility. All patients must have HER2 negative breast cancer with the identified PIK3CA mutation and received at least one line of endocrine therapy. The study will consist of a screening phase, a treatment phase, and a post-treatment phase which includes safety, efficacy, and follow-up. The treatment phase will include taking alpelisib daily in combination with continued use of either Fulvestrant or Aromatase Inhibitor per standard of care until disease progression or unacceptable toxicity.