Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Unmasking insulinoma following commencement of somatostatin analogues in malignant neuroendocrine tumours – two cases highlighting the need for vigilance when initiating therapy. (#581)

Isuru Gamage 1 , Boehm Emma 2 3 , Gaurav Ghosh 2 , Grace Kong 2 4 , Michael Michael 4 5 , HuiLi Wong 4 5 , Oliver Piercey 3 5 , Nirupa Sachithanandan 1
  1. Department of Endocrinology, Peter MacCallum Cancer Centre, Melbourne, Australia, Melbourne, Australia
  2. Molecular Imaging and Therapeutic Nuclear Medicine, Cancer Imaging, Peter MacCallum Centre , Melbourne, Victoria, Australia
  3. Centre for Cancer Research, The University of Melbourne, Melbourne, Victoria, Australia
  4. Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
  5. Department of Medical Oncology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia

Aims:Somatostatin analogues (SSA) are used in the management of metastatic pancreatic neuroendocrine tumours (pNET) to inhibit hormonal secretion and slow tumour growth. SSA can paradoxically worsen or unmask hypoglycaemia in patients with insulinoma by inhibiting counter-regulatory hormones such as glucagon and growth hormone.

Methods: We present two cases of SSA use in patients with pNET unmasking insulinoma. We review the use of SSA in pNET and management strategies for refractory hypoglycaemia caused by insulinoma.

Results: The first case is a 62-year-old female diagnosed with metastatic grade 2 pNET and commenced on the long-acting SSA lanreotide. She presented 4 months later with refractory, symptomatic hypoglycaemia, requiring inpatient dextrose infusion. Investigations revealed hyperinsulinaemic hypoglycaemia. She remained dependant on dextrose despite addition of diazoxide and dexamethasone. She underwent inpatient peptide receptor radionuclide therapy (PRRT) with 177Lutetium-DOTA-octreotate. Her hypoglycaemia responded after two cycles, and she was weaned off all medical therapy.

The second case is a 57-year-old female with metastatic grade 2 pNET. Following commencement of lanreotide, she presented with radiological disease progression and symptomatic hypoglycaemia, self-managed with frequent snacking contributing to 10kg weight gain over 4 months. A 72-hour fast confirmed hyperinsulinaemic hypoglycaemia. A trial of diazoxide was complicated by pulmonary oedema requiring inpatient diuresis. To facilitate diazoxide weaning, prednisolone was started. The patient underwent inpatient PRRT for hormone and oncologic control. Euglycaemia was achieved and diazoxide was ceased shortly afterward.

Conclusions: These cases highlight the importance of careful monitoring for hypoglycaemia following commencement of SSA for metastatic pNET initially presumed to be non-functional, given the potential to unmask insulinoma. Management of hypoglycaemia from metastatic insulinoma requires a multidisciplinary approach incorporating diet, medical and oncologic therapy. Glycaemic support with diazoxide and/or corticosteroids should occur concurrently with oncologic treatment with PRRT, everolimus or chemotherapy. The multi-receptor SSA pasireotide presents a potential future management option.