Endocrine Abstracts

Neuroendocrine tumors (NETs) constitute a rather heterogenous group of malignancies that are considered to be rare. However, resent data is indicating a significant increase in both incidence and prevalence over the last decades, with an overall incidence of 5/100 000/year and prevalence of 25/100 000/year.

The treatment of NETs is based on the tumor biology (proliferation capacity and differentiation), tumor localisation and spread (TNM-staging). Surgery is important in most patients with NETs with or without a curative intent combined with radiofrequency ablation and embolization of liver metastases. PRRT, peptide radio receptor treatment, with radioactive somatostatin analogs has increased in importance over the last years with objective response rates (PR+SD) of 30–45%. The medical treatment consists of cytotoxic agents and biologicals such as somatostatin analogs, alpha interferon, VEGF- and mTOR-inhibitors. The cytotoxic therapy consist of various agents such as streptozotocin, cisplatinum, etoposide, temozolomide, capecitabine and doxorubicin in different combinations for high proliferating tumors (Ki-67<10%). Somatostatin analogs (octreotide, lanreotide) are standard of care for functioning NETs with low proliferation capacity and Ki-67 less than 5%. The biochemical and subjective improvement are ranging from 35 to 50% with significant tumor reduction in about 5%.Treatment with non-functioning tumors with somatostatin analogs is still controversial but most resent data are indicating a benefit. Alpha interferon has been registered for mainly classical midgut carcinoids with carcinoid syndrome with biochemical and symptomatic improvement in 35–60% of the patients and tumors shrinkage in 10–15%. Both somatostatin analogs and alpha interferon can be combined. VEGF-inhibitors have been applied during the last years for treatment both as single drug but also in combinations with cytotoxic giving response rates of 10–20% and most recently mTOR-inhibitors have been applied in different subtypes of NETs with response rates between 5 and 15%.

The future treatment of NETs will be based on molecular genetics and tumor biology for personalized treatment.