Selective Internal Radiation Therapy for the Treatment of Inoperable Neuroendocrine Tumor Liver Metastases

Abstract

Neuroendocrine tumor liver metastases are commonly present at the time of neuroendocrine tumor diagnosis. Surgical resection is potentially curative and achieves the best long-term results but is not feasible in many patients. Angiographic liver-directed treatment modalities such as transarterial embolization, transarterial chemoembolization and selective internal radiotherapy using Yttrium-90 ([90]Y)-labeled microspheres have been shown to be effective treatments with liver predominant disease. Here, we review the management of neuroendocrine tumor liver metastases including selective internal radiotherapy. BodyNeuroendocrine tumors (NETs) are a broad family of malignancies that arise from the diffuse endocrine system. The estimated age-adjusted incidence has been increasing with 5.25 cases per 100,000 people with the most common sites being the gastrointestinal tract and lungs [1,2]. The most common tumor types are carcinoid and pancreatic NETs (pNETs) [2]. NETs are known for their ability to produce hormonally active peptides that cause their characteristic syndromes and classify them as 'functional' tumors, the symptoms of which can vary from intermittent cutaneous flushing and secretory diarrhea in carcinoid syndrome, resistant hypertension in pheochromocytoma and symptoms resulting from the hypersecretion of gastrin, insulin, glucagon and other peptides in pNETs. Despite the slow growing nature of these tumors and their significantly better survival profiles when compared with adenocarcinomas of the same location, their peptide products usually cause their characteristic syndromes upon metastases, which correlates with the high incidence of metastatic disease upon diagnosis [3,4].Of the metastatic sites, between 30 and 95% of NETs present with liver metastases at the time of diagnosis and this remains the most significant negative prognostic marker for survival regardless of primary disease site [4][5][6][7][8][9][10][11][12]. 5-year survival rates for NET liver metastases (NETlms) are less than 20% compared with 67-99% when NETs present without metastases [4,7,8,[13][14][15]. Surgical resection for NETlms is the most effective treatment modality as it offers immediate symptom control and improved long-term survival with 5-year survival rates between 47 and 76% [14,[16][17][18][19][20]. In a large multicenter international cohort of patients undergoing surgical management of NETlms, Mayo et al. reported the 5-and 10-year survival rate to be 74 and 51%, respectively, which is higher than has been reported by other studies although 5-and 10-year recurrence rates remained high at 94 and For reprint orders, please contact: reprints@futuremedicine.com