A 64-year-old man (HM) was admitted to our local hospital with transient dysarthria and right hemiparesis; formal blood glucose was 2.2 mmol/l on admission. During his in-patient stay, he had frequent episodes of hypoglycaemia. Further questioning revealed a 4 week history of recurring dizzy spells which improved on eating.
Cerebral imaging and adrenal function were normal and so the patient underwent further investigations (summarised below) which confirmed insulinoma.
|Insulin (<13 mU/l)||166||172||136|
|C-peptide (0.41.1 nmol/l)||1.8||1.7||1.5|
|Insulinglucose ratio (<5)||276||429||680|
In addition, plasma chromogranin-A was elevated (590 pmol/l) consistent with a neuroendocrine tumour. Abdominal imaging demonstrated a thickened pancreatic tail and widespread liver metastases; these were octreotide avid on octreoSPECT-CT scanning. Subsequent liver biopsy confirmed metastatic insulinoma.
Primary surgical cure was impossible and HM required a combination of diazoxide, octreotide and dexamethasone to control hypoglycaemia. HM subsequently underwent transhepatic arterial embolisation to treat his metastatic liver disease. This has resulted in normalisation of blood glucose on sandostatin LAR and reducing dose dexamethasone.
Insulinomas are rare tumours of the pancreatic islet cells with an incidence of ~4 per million/year; around 510% of cases are malignant. When surgical cure is unattainable alternative palliative treatments include medical therapy, radiofrequency ablation or arterial embolisation to hepatic metastases. The response rates associated with embolisation (decreased hormone secretion/symptomatic benefit/ radiographic regression) are over 50%. However, the duration of response can be brief, ranging from 4 to 24 months in uncontrolled series.
Everolimus, a rapamycin analogue, is a new oral mTOR inhibitor. In a recent study, everolimus associated with regression of neuroendocrine tumours and there have been some case reports of everolimus improving glycaemic control in insulinoma. This would be a possible alternative therapy for HM when he relapses.