Current Treatment Options in Neuroendocrine Tumors of the Appendix

While appendiceal neuroendocrine tumors (aNETs) are rare, they are the most common type of appendiceal neoplasms, often discovered incidentally during surgeries for acute appendicitis. Appendiceal NETs are typically well-differentiated and associated with an excellent prognosis after adequate surgical therapy.

Management of aNETs depends on tumor size, grade, and risk factors for lymph node and metastasis. Current guidelines from the European Neuroendocrine Tumor Society (ENETS) recommend appendectomy only for low-risk tumors (<1 cm) and more extensive resection (right hemicolectomy [RHC]) for high-risk tumors (>2 cm or incomplete resection). However, the management of intermediate-sized tumors (1-2 cm) remains debated as RHC may not improve survival. Risk factors such as lymphovascular invasion or mesoappendiceal infiltration over 3 mm may prompt RHC consideration. However, current evidence suggests that long-term outcome is not affected by the extent of surgery in aNETs 1-2 cm in size questioning the necessity of RHC in these cases. Advanced metastatic aNETs, extremely rare in occurrence, follow treatment guidelines similar to other gastroenteropancreatic NETs and may involve multimodal therapy, including surgery, radiological interventions, and systemic treatment tailored to the patient's condition and disease burden.

Appendectomy is adequate for most aNETs, particularly those smaller than 1 cm, G1, and without high-risk features. RHC is recommended for tumors larger than 2 cm, but for tumors 1-2 cm, evidence increasingly suggests that RHC may not confer a survival benefit. Metastatic aNETs are rare, and individualized, multidisciplinary therapy approaches are recommended.