Severe resistant hypoglycemia in a patient with a pancreatic neuroendocrine tumor on sunitinib treatment

OBJECTIVE: Sunitinib is a tyrosine kinase inhibitor used in the therapy of pancreatic neuroendocrine tumors (PNETs), metastatic renal cancer and gastrointestinal stromal tumors. We describe a patient with PNET who presented with severe hypoglycemia following sunitinib administration. CASE REPORT: A 64-year old man with known metastatic PNET presented with a history of recurring episodes of severe, life-threatening hypoglycemia 3 months after initiation of sunitinib treatment. Investigations during symptomatic hypoglycemia revealed inappropriately increased plasma insulin and C-peptide levels, consistent with endogenous hyperinsulinemia. No immune staining for insulin was observed in tissue samples from peritoneal metastatic tumor lesions, and serum anti-insulin antibodies were negative. Medical management with diazoxide, methylprednisolone and ocreotide was ineffective; continuous intravenous infusion of glucagon was required to maintain euglycemia. Following discontinuation of sunitinib there was gradual improvement in both the severity and frequency of the hypoglycemia. Six months later, the patient remained free of hypoglycemic episodes. CONCLUSIONS: We describe a patient with PNET who experienced severe, life-threatening hypoglycemia following sunitinib use. It is important that glucose levels of patients treated with sunitinib are monitored on a regular basis; those patients with diabetes may need to have their antidiabetic treatment adjusted to prevent hypoglycemia.