Managing Hyperglycemia and Diarrhea in PIK3CA-Mutated HR+/HER2-Negative Advanced Breast Cancer

Dr. Jason Mouabbi revisits the patient's Grade 2 hyperglycemia at week 6, when fasting glucose reaches 212 mg/dL. The care team initiates antihyperglycemic therapy and temporarily withholds inavolisib, with glucose improving to 150 mg/dL within 5 days and treatment subsequently resumed at the same dose. The discussion then shifts to diarrhea, another important treatment-related adverse event in PIK3CA-mutated HR-positive/HER2-negative advanced breast cancer. Dr. Mouabbi emphasizes counseling patients about the possibility of diarrhea from the start of treatment and preparing them to recognize symptoms and initiate supportive management early. He discusses the use of loperamide for mild diarrhea, along with maintaining adequate oral fluid intake to reduce the risk of dehydration. He also reviews how diarrhea severity influences treatment management, including continuation of therapy for lower-grade symptoms and treatment interruption and potential dose modification when symptoms become more severe or recur. The segment highlights proactive patient education and early intervention as key components of adverse-event management.