Aggressive Metastatic Insulinoma in a Patient of Diabetes Mellitus with Documentation on Dual-Tracer PET-CT ([68Ga]Ga-DOTATATE and [18F]FDG): Clinical Benefits with Combined Chemo-PRRT Approach

Insulinoma is a relatively uncommon pancreatic neuroendocrine tumor, with approximately 10% of the cases being malignant. Diabetes mellitus (DM) with concurrent insulinoma is very rare and the diagnosis of such condition is easily missed as it can be misconstrued as improved glycemic control. Therefore, persistent hypoglycemic symptoms even after stopping antidiabetic medications may be considered for insulinoma. Herein, we present a patient with DM and pancreatic insulinoma with extensive hepatic and skeletal metastases on dual-tracer positron emission tomography/computed tomography (PET/CT) ([68Ga]Ga-DOTATATE and [18F]fluorodeoxyglucose). Given the extensive disease, the patient was treated with a combination of peptide receptor radionuclide therapy (PRRT) and chemotherapy (capecitabine and temozolomide). During therapy, patient showed early clinical and imaging response for insulinoma leading to unmasking of poor glycemic control necessitating requirement of insulin administration for DM. The patient did not experience any life-threatening hypoglycemia during the chemo-PRRT treatment and showed an improvement in quality of life. Unfortunately, the disease progressed at the 4th cycle, 10 months after the initiation of PRRT. We conclude that combined chemo-PRRT may be considered an effective treatment option for patients with metastatic insulinoma and DM owing to its favorable imaging response and effective symptom control.