Small intestinal neuroendocrine tumors (carcinoids) are the most common neuroendocrine tumor (NET) within the gastrointestinal tract (15–20%). The incidence and prevalence is steadily increasing during the last decade and the estimated incidence is now about 2.5/100 000/year. The majority of the tumors produce peptides and amines giving rise to clinical symptoms related to the hormone production such as the carcinoid syndrome with flushing, diarrhea, bronchial constriction, and carcinoid heart disease. The majority of patients present with metastatic disease (60%) and therefore a surgical cure is not obtainable. The medical treatment consists of somatostatin analogs, alpha interferons, and targeted treatment with mTOR- and tyrosine kinase-inhibitors. Somatostatin analogs are still the gold standard for treatment of carcinoid tumors with hormone-related clinical symptoms. A possible antitumor effect has been debated, but a recent study (PROMID) has demonstrated an antitumor effect of octreotide LAR, 30 mg, every 4 weeks versus placebo. Tyrosine kinase inhibitors have been applied mostly for antiangiogenic purposes with objective responses in 10–20% of the patients and PFS of 10–15 months. The mTOR-inhibitor everolimus have demonstrated an antitumor effect in patients with carcinoid tumors in the RADIANT-2 trial. Cytotoxic treatment has demonstrated a limited efficacy in classical low proliferation well-differentiated neuroendocrine gastrointestinal tumors and should not be considered first-line treatment. The future treatment will be based on tumor biology and molecular genetics taking into account the new classification systems. The treatment will be personalized.
