Pancreatic insulinomas are rare functional neuroendocrine tumours which cause excessive insulin release and recurrent hypoglycaemia. Diagnosis can be challenging, with the 3 day fast test a significant burden on patients and resources. Surgery is the mainstay of treatment, with medical therapy used for bridging or for non-surgical management. This is the case of an 85 year old male referred for a vague history of hypoglycaemia. His background included smoldering myeloma, non-small cell lung cancer, epilepsy, and chronic lower limb lymphoedema. After a difficult and delayed diagnosis of insulinoma, he poorly tolerated medical therapy. After MDT discussion, conservative treatment with Stereotactic Body Radiation Therapy (SBRT) was used.
The diagnosis of insulinoma was complicated by a recent misdiagnosis of epilepsy and hypoglycaemic unawareness with no strong evidence of Whipple’s triad. Diagnosis was made after an unrelated admission in which a hypoglycaemic seizure occurred with biochemistry revealing low glucose (2.5 mmol/L), elevated S-Insulin (22 U/L), pro-insulin (>100 pmol/l) and C-Peptide (1.6 nmol/L) with low beta-hydroxbutyrate (0.04 mmol/L). Magnetic resonance imaging revealed 2.3 cm pancreatic head lesion, which was intensely avid on DOTATATE PET.
The patient was commenced on Diaxoxide at 200 mg twice daily however dosing proved difficult due to fluid overload and renal dysfunction and careful titration was required with the use of Continuous Glucose Monitoring (CGM). Given the patient's age, surgical risk and difficulty with diazoxide, a multidisciplinary team opted for conservative management with SBRT. The patient responded well to SBRT, experiencing reduced hypoglycemia. Gradually tapering off diazoxide over three months post-treatment, he continues under long-term observation.
In conclusion, this case underscores the promise of SBRT as a viable non-surgical alternative for managing insulinomas patients with substantial surgical risks. Additionally, it underscores the importance of considering hypoglycemia unawareness when initially attempting to establish Whipple’s Triad in the investigation of non-diabetic hypoglycaemia.