Endoscopic Ethanol Ablation as Definitive Therapy for Suspected Insulinoma

Introduction: Hypoglycemia is defined as plasma glucose <70mg/dL, with autonomic and/or neuroglycopenic symptoms often occurring at levels less than 55mg/dL. Diagnostic workup of hypoglycemia unrelated to use of hypoglycemic agents is crucial as it is linked to increased mortality. After ruling out common culprits such as drugs (insulin, sulfonylureas), ethanol and malnutrition, further testing should be pursued for patients who meet the Whipple’s Triad: symptoms of hypoglycemia, documented low plasma glucose and relief of symptoms upon raising plasma glucose. We present the case of an 85-year old male with a suspected insulinoma who underwent endoscopic alcohol ablation as definitive therapy. Case: An 85-year-old male with a history of metastatic prostate cancer was found to have recurrent episodes of asymptomatic hypoglycemia with fasting plasma glucose levels as low as 50-60s during an unrelated inpatient admission. He had no history of diabetes mellitus or insulin use. On further investigation, he was noted to have recurrent falls, though these symptoms could not be temporally linked to documented hypoglycemia as the patient was not monitoring blood sugars at home. Further workup revealed fasting plasma glucose of 58mg/dL and negative sulfonylurea screen. Plasma C-peptide and fasting plasma insulin levels during an episode of hypoglycemia were elevated at 6.42ng/mL and 38uIU/mL respectively. IGF-II and insulin autoantibody testing was negative. Abdominal imaging revealed a 1.3cm hypervascular pancreatic head lesion consistent with a neuroendocrine tumor, concerning for an insulinoma in view of his lab findings. Surgical removal of this lesion was not within the patient’s goals of care. Attempts at medical management included escalating doses of prednisone and subcutaneous octreotide; however, he continued to have hypoglycemic episodes despite therapy. His cardiac history precluded the use of other medical therapies. After careful evaluation, he underwent ultrasound-guided ethanol ablation of his neuroendocrine tumor as potential definitive therapy, with successful resolution of hypoglycemic episodes noted during his post-procedural hospital stay. Discussion: Traditionally, insulinomas are primarily managed surgically. Poor surgical candidates can benefit from medical management including diazoxide, somatostatin analogs and verapamil among others. Ultrasound-guided ethanol ablation is a newer modality aimed achieving cure in selected patients, thus avoiding need for surgery. Our case highlights the challenges in management of insulinomas, especially in complicated patients like ours who are not surgical candidates and who may be resistant to medical therapy. Though there are not many studies on the long-term efficacy and outcomes with ethanol ablation of insulinomas, it appears to be a promising option and certainly deserves further study.