Study Assessing the Efficacy, Safety and PK of Alpelisib (BYL719) in Pediatric and Adult Patients With PIK3CA-related Overgrowth Spectrum

Key Inclusion Criteria: * Signed informed consent and assent (when applicable) from the patient, parent, legal authorized representative, or guardian prior to any study-related screening procedures were performed. * Male or female patients age above 0 day at the time of informed consent: Group 1: ≥ 18 years old, Group 2: 6-17 years old, Group 3: ≥ 0-5 years old, Group 4: ≥ 2-5 years old, Group 5: 6-17 years old. * Patients with diagnosis of PROS with symptomatic and /or progressive overgrowth and at least one measurable PROS-related lesion confirmed by BIRC assessment who had syndromic disease or isolated features at the time of informed consent. Patients, who previously had been receiving systemic treatment for PROS, could enter the study. * Documented evidence of a somatic mutation(s) in the PIK3CA gene performed in local laboratories using a DNA-based test validated according to the local regulations at the time of informed consent. * A tissue sample (fresh or archival) was to be sent to a Novartis-designated central laboratory. * Karnofsky (in patients \> 16 years old at study entry)/Lansky (≤ 16 years of age at study entry) performance status index ≥ 50. * Adequate bone marrow and organ function as assessed by central laboratory for eligibility. * Presence of at least one PROS-related measurable lesion defined as a lesion with longest diameter ≥ 2 cm, when the volume could be accurately and reproducibly measured by MRI, and associated with complaints, clinical symptoms …