Inclusion Criteria:  Participants who had previously participated in the study EPIK-P1. Signed informed consent form and assent (when applicable) from the participant, parent, or guardian must be obtained prior to any study related screening procedures being performed. Participant is treated with at least one dose of alpelisib after the EPIK-P1 study data cut- off date of 09-Mar-2020.  Exclusion Criteria:  For participants in the retrospective period  - All EPIK-P1 participants who permanently discontinued the investigational drug on or prior to the cut-off date 09-Mar-2020.  For participants in the prospective period  Previous alpelisib treatment discontinuation (after 09-Mar-2020) due to any of the following adverse events:  Grade 4 skin and subcutaneous tissue disorders Stevens-Johnson-Syndrome (SJS)/ Toxic Epidermal Necrolysis (TEN) or other SJS/TEN-like severe skin reactions (any grade) Grade 4 hyperglycemia without confounding factors Pneumonitis (any grade) Grade 4 stomatitis Grade 4 pancreatitis Recurrent grade 4 thrombocytopenia Grade 3 or 4 serum creatinine increase Grade 4 isolated total bilirubin elevation Recurrent grade 3 or 4 QT interval corrected by Fridericia's formula prolongation (>500 ms or >60 ms change from baseline) Known impairment of GI function due to concomitant disease that may significantly alter the absorption of the study drug (e.g., ulcerative diseases, uncontrolled nausea, vomiting, diarrhea, malabsorption syndrome, or small bowel resection) at time of informed consent. Participant with uncontrolled diabetes mellitus (Type I or II) at time of informed consent.  Other inclusion/exclusion criteria may apply