Locoregional and radioisotopic targeted treatment of neuroendocrine tumours.

Gastro-entero-pancreatic neuroendocrine tumours (GEP NET) are a heterogeneous group of proliferative disorders whose management dramatically relies on tumour biology. For well-differentiated, low-proliferative index tumours, locoregional treatment and targeted radioisotopic therapies offer an attractive and seemingly efficient alternative to palliative surgical resections. Lack of well-designed, prospective, randomized multicentric studies hinders a balanced evaluation of available locoregional treatment methods: embolization, chemo-embolization, radio-embolization. According to available datas, all techniques achieve a 50-60% radiological response rate and almost 80% of symptomatic relieve for the patients, while their impact on progression-free and overall survival remains not assessable. Same conclusions can be drawn for radiolabeled targeted therapies like MetaiodoBenzylGuanidine (MIBG) and Peptide Receptor Radionuclide Therapy (PRRT), which, provided that their target is expressed by tumour cells, can deliver therapeutic doses of radiation to neoplastic tissues. 131I-MIBG has been associated with a 50% symptomatic response rate and mainly haematological toxicities. PRRT with 111In-DiethyleneTriamineentaacetic Acid-Octreotide, [90Y-DOTA0-Tyr3]-Octreotide, or [177Lu-DOTA0-Tyr3]-Octreotate seem to alleviate symptoms in 50% of patients and obtain a radiological response in 30-38%. Renal toxicity, partially preventable, is more frequent than previously thought and result in an annual decrease in glomerular function by 4 to 8% per year. Forthcoming research in GEP NET should by a majority be designed in randomized, prospective and multicentric fashion. Locoregional disease trials must focus on clinical outcome differences between embolization techniques (embolization, chemoembolization and radioembolization) and surgery. In disseminated disease, studies should assess radiolabeled targeted therapies efficiency when administered along with and compared to new biological and older chemotherapeutic agents.

The role of surgery and transplantation in neuroendocrine tumours.

Surgery represents the only chance of cure for a patient with a neuroendocrine tumour (NET). The main indications for surgery lie in the risk of developing metastatic disease with increasing tumour diameter and for a functioning NET also in control of the hormonal syndrome. However, only a small minority of patients presents with a potentially resectable primary NET without metastatic disease. An R0-resection is mandatory, which may be achieved in selected cases by tissue sparing surgical techniques. Most patients unfortunately present with a locally advanced or metastatic disease. For patients with an advanced functioning NET, control of the hormonal syndrome may also represent a surgical indication. Various cytoreductive techniques or, in highly selected cases, liver transplantation can be applied. For locally advanced non-functioning tumours, there is an indication for surgery in large tumours which tend to create local complications because of bleeding or bowel obstruction. Especially in ileal NETs aggressive surgical therapy is recommended because of prevention of long-term complications, which may improve survival.