Poster Presentation ESA-SRB-APEG-NZSE 2022

The importance of using complementary imaging modalities A case of metastatic insulinoma not identified on GA-68 DOTATATE PET (#330)

Arunan Sriravindrarajah 1 2 , Julie T Hetherington 1 3 , Kirby Wong 1 , Angelique Brescia 1 , Cale Fletcher 1 , Joo-Shik Shin 1 2 , Kate Mahon 4 5 , Charbel Sandroussi 1 2 4 , Albert Hsieh 1 2 , Samantha L Hocking 1 2 6 , Stephen M Twigg 1 2 6
  1. Royal Prince Alfred Hospital, Camperdown Sydney, NSW, Australia
  2. Faculty of Medicine and Health, University, Sydney, NSW, Australia
  3. Susan Wakil School of Nursing and Midwifery, University of Sydney, Sydney, NSW, Australia
  4. Chris O'Brien Lifehouse , Sydney, NSW, Australia
  5. Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
  6. Charles Perkins Centre, University of Sydney, Sydney, NSW, Australia

Insulinoma is the most common functioning pancreatic neuroendocrine tumour, yet remains uncommon with 4 cases per million person years1. Metastatic insulinoma is exceedingly rare, comprising only 6% of insulinomas2. Localisation of neuroendocrine tumours can be performed via Ga-68 DOTATATE-PET, a functional imaging modality where the tracer binds to Somatostatin subtype 2 receptors, which are often expressed in insulinomas3.

 

A 64-year-old Caucasian male was investigated for recurrent severe episodes of feeling unwell which satisfied Whipple’s Triad for hypoglycaemia. Biochemical investigations after a limited fast demonstrated a formal plasma glucose level of 1.7mmol/L with inappropriately detectable C-peptide 0.40nmol/L (0.4-1.5), insulin 8mU/L (0-20) and pro-insulin 48.5pmol/L (<13.3), which suggested an insulinoma. Ga-68 DOTATATE-PET scan identified focal uptake in the body of the pancreas (SUV 9.7) but nil metastatic lesions. CT Abdomen and MRI Pancreas confirmed a pancreatic lesion, but also identified multiple arterial enhancing liver lesions. Surgical resection of the pancreatic and liver lesions were performed with histopathology of the lesions confirming the presence of a Grade 2 Neuroendocrine Tumour. Post-operative MRI identified multiple persistent liver lesions, but repeat Ga-68 DOTATATE-PET scan only identified a single avid liver lesion (SUV 27.2). Treatment with diazoxide, dexamethasone, cornstarch, Flash #2 glucose monitoring and Sandostatin LAR delivered an initial improvement in glycaemia. A glucagon stimulation test showed safety in its emergency administration. Ongoing therapy is being guided by a multidisciplinary team specialising in Neuroendocrine tumour care, with planned Lutate therapy.

 

This case demonstrates the unusual situation where Ga-68 DOTATATE PET localised the primary insulinoma lesion, but not metastatic liver lesions. Repeat Ga-68 DOTATATE PET was subsequently able to identify a large metastatic liver lesion, although several other liver lesions remain undetected. This case highlights the importance of serial anatomical and functional imaging for the diagnosis and localisation of metastatic neuroendocrine tumours.

  1. Secular trends in the presentation and management of functioning insulinoma at the Mayo Clinic, 1987-2007, Plackowski et al., 2009. JCEM, 94(4): 1069-73
  2. Functioning insulinoma--incidence, recurrence, and long-term survival of patients: a 60-year study, Service et. al. 1991, Mayo Clin Proc, 66(7):711-9
  3. Somatostatin receptors 2 and 5 are the major somatostatin receptors in insulinoma: an in vivo and in vitro study, Bertherat et. al. 2003, JCEM, 88(11):5353-60