Management of Locally Advanced and Unresectable Small Bowel Neuroendocrine Tumours

Three subtypes of small bowel neuroendocrine tumours (SBNETs) have been described: Type A: SBNET with resectable mesenteric disease that does not involve the mesenteric root; Type B: "Borderline resectable" SBNET presenting with mesenteric nodal metastases and fibrosis adjacent but not encasing the main trunk of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV); and Type C: "Locally advanced or irresectable" SBNET where tumour deposits and fibrosis encase the SMA and SMV. Type C SBNETs are rare and constitute around 5% of patients in reported series, although this may underestimate the prevalence. In these patients, almost all will present with symptoms of intestinal ischemia or obstruction and symptom management should be a primary main focus of treatment. All patients should be carefully staged with cross-sectional imaging and 68 Ga-dotate positron emission tomography, and discussed at a dedicated neuroendocrine tumour multidisciplinary meeting. Expert surgical review should always be sought as experienced centers have a high rate of successful resection of primary tumours and mesenteric disease. If resection is not feasible, surgical bypass should be considered in patients with a discrete and symptomatic point of obstruction. Non-operative management should emphasize symptomatic treatment with somatostatin analogs, nutritional advice and support and palliative care. Successful neoadjuvant approaches utilizing peptide radionucleide receptor therapy and systemic chemotherapy with everolimus or temazolamide/capecitabine have not been reported.