SUN-314 Gallium-68 DOTATATE PET/CT for Preoperative Localization of Metastatic Insulinoma

Introduction Metastatic insulinoma is a rare clinical entity. Preoperative localization of metastatic insulinoma in the setting of multiple hepatic lesions represents a challenge, as it can coexist with noninsulinoma hepatic lesions(1). Gallium-68 DOTATATE was first FDA-approved for the localization of neuroendocrine tumors in mid-2016 and has demonstrated effectiveness for insulinoma(2). We present a case where multiple lesions were present in the setting of metastatic insulinoma and Ga-68 DOTATATE PET/CT was utilized in localizaton. Case Report A 37-year-old female with a history of pancreatic insulinoma s/p resection via Whipple procedure in 2007 presented to the ED with a five-day history of visual changes and lightheadedness concerning for hypoglycemia. Abdominal CT obtained in the ED demonstrated a low-attenuation lesion in the hepatic dome. TFTs were normal and cosyntropin stimulation testing was unemarkable. A subsequent 72-hour fast ended after < 12 hours due to symptomatic hypoglycemia; BGL was 55mg/dl and insulin level was 31.5 mU/L, confirming a hyperinsulinemic etiology. Sulfonylurea screen was negative. Abdominal MRI demonstrated a 1.1 cm mass within hepatic segment VIII, as well as additional lesions in segment VIII and at the junction between VIII and VII. Due to uncertainty regarding which of the hepatic lesions represented recurrent metastatic insulinoma, Ga-68 DOTATATE PET/CT scan was pursued; this demonstrated a 1.3 cm focus of increased activity consistent with neuroendocrine tumor metastasis in hepatic segment VIII. The other lesions were not DOTATATE-avid. Resection of the 1.3 cm lesion demonstrated a 1.1 cm tumor with cells positive for chromogranin, synaptophysin, and scattered weak positivity for insulin. While one episode of hypoglycemia did occur shortly after surgery, there was no further symptomatic hypoglycemia on outpatient follow-up. Present plan includes repeat Ga-68 DOTATATE PET/CT six months postoperatively. Conclusion Localization of metastatic insulinoma in the setting of multiple hepatic lesions on traditional imaging modalities represents a challenge. While Ga-68 DOTATATE PET/CT has been shown to be an effective tool in insulinoma localization, there is a paucity of literature regarding its utility in the setting of suspected recurrent metastatic insulinoma. We present a case where Ga-68 DOTATATE PET/CT was effectively utilized in preoperative localization of metastasis in the setting of multiple hepatic lesions. Further research into this area with prospective data regarding clinical recurrence is warranted. References 1. Jerraya H, Zidi-Mouaffek Y, Dokmak S, Dziri C. Insulinoma with focal hepatic lesions: malignant insulinoma? BMJ case reports 2015;2015. 2. Nockel P, Babic B, Millo C, et al. Localization of Insulinoma Using 68Ga-DOTATATE PET/CT Scan. The Journal of clinical endocrinology and metabolism 2016;102:195-9.