Atypical location and treatment for a rare neuroendocrine tumour
Heba El-Gayar, Daniel Morganstein & Karim Meeran
Somatostatinomas are rare neuroendocrine tumors usually arising from the pancreas and duodenum. Symptoms include hyperglycemia, cholelithiasis, diarrhea and steatorrhoea. Treatment with somatostatin (SST) analogue may appear paradoxical, but can lower SST levels and improve symptoms.
Case: A 60-year-old gentleman presented with diarrhoea, opening his bowels between 12 and 13 times a day causing him to stop working and become depressed. Repeated fasting gut hormone profiles showed an isolated elevated SST levels. CT abdomen did not show any pancreatic lesions and colonoscopy was normal. Octreotide scan revealed a well defined lesion in the base of the right lung, confirmed on a CT thorax. Visceral angiography with calcium stimulation and sampling from the femoral artery revealed elevated SST in all samples (>400 pmol/l). SST levels taken from the right atrium and femoral artery, showed a higher level in the arteries (venous 152 pmol/l, arterial 185 pmol), suggesting a pulmonary source. However, the surgical risks of resection were thought to be high. He had a trial of Octreotide therapy without benefit. Four years later, he was treated with a combination of Lanreotide 30 mg every 14 days, and Octreotide 50 mcg TDS, resulting in a dramatic improvement in symptoms. He now opens his bowels once or twice a day. His symptoms worsened when Octreotide was withdrawn. He also noticed two days prior to the lanreotide injection be opens his bowels more frequently.
Discussion: There are 5 subtypes of somatostatin receptors (SSTR). All five SSTRs bind to the natural SST. Two different SST analogues are used clinically, octreotide and lanreotide. These analogues bind principally to the receptor subtype 2 and 5. Although most studies have shown no major difference between octreotide and lanreotide in terms of receptor affinity or biological activity, this case illustrates that combination therapy may have clinical benefits.