A Pilot Study of Monitoring Insulin Levels and Treating Hyperinsulinemia and Hyperglycemia With Pioglitazone in Patients Treated With Alpelisib for Metastatic Breast Cancer.

This study is monitoring insulin and blood sugar levels in breast cancer patients taking alpelisib (a targeted cancer drug) and testing whether adding pioglitazone (a diabetes medication) can control high blood sugar — a common and often treatment-limiting side effect of alpelisib. **You may be eligible if...** - You have ER-positive, HER2-negative metastatic breast cancer - Your tumor has a PIK3CA mutation (a specific genetic change) - You are about to start treatment with alpelisib and fulvestrant - You are between 18 and 85 years old - You are in reasonably good health (ECOG 0–2) **You may NOT be eligible if...** - You have uncontrolled diabetes - You have serious gastrointestinal problems that would affect medication absorption - You have significant liver, kidney, or heart problems that could interfere with the study drugs Talk to your doctor to see if this trial is right for you.