Supplementary Material for: First Experiences with Alpelisib in Clinical Routine: Case Reports from a German Breast Center

<b><i>Introduction:</i></b> The phosphatidylinositol-3-kinase (PI3K) inhibitor alpelisib is the only approved agent for treating ­<i>PIK3CA</i>-mutated, hormone receptor-positive (HR+) human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (ABC). Trials have reported hyperglycemia, diarrhea, and rash as the main grade 3 side effects. <b><i>Methods:</i></b> In a managed access program (ClinicalTrials.gov ID: NCT03706573; start: 06/2019), 8 HR+ HER2– ABC patients with a median 4.5 prior therapy lines were treated with alpelisib at the Breast Center of the Ludwig-Maximilian University (LMU) Hospital, Munich, based on the results of a new-generation sequencing (NGS) panel and <i>PIK3CA</i> mutation analysis by the Molecular Tumor Board of the Comprehensive Cancer Center, Munich. <b><i>Results:</i></b> Median therapy duration was 3.42 months for patients who discontinued and 3.95 months for those still on alpelisib (4 pts). Five had hyperglycemia (1 with grade 3) with fasting glucose levels of up to 450 mg/dL that required hospitalization and insulin therapy. Two experienced rash (grades 1 and 3) and 2 reported grade 3 diarrhea. Supportive therapy as well as interruption and/or dose reduction were necessary to control treatment-associated side effects. <b><i>Conclusion:</i></b> Patient education and a well-trained, interdisciplinary team including diabetologists, from the initiation of alpelisib treatment onwards, are essential to safely treat ABC patients with this new drug and to maintain their quality of life and ensure their survival.