Use of alpelisib in the treatment of hormone receptor positive metastatic breast cancer: An institutional experience.

e15216 Background: Mutations in PI3K pathway is a known mechanism of resistance to endocrine therapy in breast cancer. Alpelisib is an alpha-specific PI3K inhibitor. Alpelisib with Fulvestrant is approved for treatment (Tx) of PIK3CA mutated HR+ metastatic breast cancer (MBC) that progress on hormonal therapy. Despite its approval by the FDA, real world data on the use of Alpelisib for the management of MBC is lacking. This abstract reviews the safety and efficacy of Alpelisib in the management of patients with MBC. Methods: A retrospective review of the tumor registry database at a single institution was conducted to identify patients with HR+ MBC. Detailed clinical and pathologic data of PIK3CA mutated patients treated with Alpelisib were obtained. Genomic profiling was done with Foundation One. Results: Table highlights the characteristics of the four patients. All were treated with Alpelisib and Fulvestrant after PIK3CA mutation was demonstrated. 3 patients were heavily pretreated with systemic Tx including CDK 4/6 inhibitors. All patients responded to Alpelisib and Fulvestrant despite treatment history. Mucositis, rash, hyperglycemia and pancytopenia were the observed adverse events (A/E). All A/E were adequately managed except in one patient that required discontinuation of Tx. None has clinically progressed. Conclusions: Our data suggests that Alpelisib and Fulvestrant is tolerated and improves outcomes in patients with HR+ MBC. Alpelisib and Fulvestrant could be an effective therapy in patients who have also progressed on systemic chemotherapy including CDK 4/6 inhibitors. Although our sample size is small, we hope that our experience could guide clinicians in the management of patients with HR+ MBC who harbor the PIK3CA mutation and are being treated with Alpelisib. [Table: see text]