A80-3-07 Piqray Induced Hyperglycemia Complicated by Massive Pleural Effusion in a Patient With Metastatic Breast Cancer

Background Alpelisib (Piqray) is a PI3Kα inhibitor approved for HR+/HER2-, PIK3CA-mutated metastatic breast cancer. Hyperglycemia is a known side effect; however, its progression to severe metabolic and fluid complications, such as massive pleural effusion, is rare. Case Summary A 65-year-old woman with metastatic breast cancer (PIK3CA-mutated) developed severe hyperglycemia (glucose 450 mg/dL) and diabetic ketoacidosis within three weeks of starting alpelisib. Despite discontinuation and insulin therapy, she developed progressive massive pleural effusion, hypoalbuminemia, and respiratory compromise. Management included thoracentesis, intravenous albumin, intensified diuresis, fluid restriction, and strict glucose control. Clinical improvement occurred by day 6, with effusion resolution on imaging, weight reduction from 82 kg to 76 kg, and normalization of respiratory status. Results Following discontinuation of alpelisib, the patient achieved metabolic stabilization and resolution of the pleural effusion. At six-month follow-up, she remained stable on fulvestrant monotherapy with no recurrence of hyperglycemia or effusion. Conclusion Alpelisib can trigger severe hyperglycemia and systemic capillary leak leading to massive pleural effusion. Early recognition, multidisciplinary management, and individualized metabolic monitoring are crucial to prevent morbidity and ensure safe oncologic continuation. Keywords: Alpelisib, hyperglycemia, pleural effusion, breast cancer, PIK3CA mutation, case report. This abstract is funded by: None