Radioembolization for neuroendocrine tumors: procedure, application and clinical outcomes

Abstract

Neuroendocrine liver metastases significantly affect patient prognosis and quality of life due to their symptomatic burden and challenging management. Besides conventional systemic therapies, liver-directed therapies improve patient outcomes in patients with liver-dominant disease. These liver-directed therapies have gained interest over the past decade, but their placement in the treatment algorithm of neuroendocrine liver metastases remains largely unclear. The purpose of this review is to evaluate the current role of selective internal radiation therapy (radioembolization) as a treatment for neuroendocrine liver metastases. This review examines the patient selection, procedural aspects, applications, and clinical outcomes. Radioembolization is effective as a standalone treatment. This treatment achieves disease control rates exceeding 90% and improves symptoms and quality of life. Moreover, combining radioembolization with systemic therapies may provide improved treatment response and additional benefits, but further investigation is required. The treatments effectiveness is influenced by appropriate patient selection, including consideration of liver function, tumor vascularity and previous interventions. A multidisciplinary approach is essential in assessing treatment eligibility. Patient management should be tailored on an individual level to optimize outcomes. The incidence of complications is rare (<1%), with radiation-induced liver disease being the most concerning. This review underscores the need for continued research to better understand the optimal use of radioembolization. Specifically, its placement within treatment, particularly in combination with other therapies, requires further exploration, ultimately to improve survival and quality of life for patients with neuroendocrine liver metastases.

Keywords: NET; SIRT; neuroendocrine neoplasm; radioembolization.

Figure 1

The step-by-step process of radioembolization. Abbreviations: SPECT, single-photon emission computerized tomography; CT, computed tomography.

Figure 2

¹⁶⁶Ho-radioembolization in a 70-year-old patient with liver metastases of a grade 2 insulinoma. Progressive liver-only disease (after pancreatic tail resection) with clinically multiple hypoglycemic episodes daily. Previous treated with on somatostatin analogs, followed by [¹⁷⁷Lu]Lu-DOTATATE (prematurely ceased after three cycles of 7.4 GBq due to grade 2–3 pancytopenia). (A) Pre-treatment arterial phase contrast-enhanced CT (CECT) showing bilobar hypervascular metastases (largest lesion is 40 mm in maximum diameter). (B) [^99mTc]Tc-MAA SPECT-CT and (C) maximum intensity projection (MIP) of [^99mTc]Tc-MAA showing good intrahepatic distribution of the particles without extrahepatic deposition. Following patient-tailored treatment (dosimetry: normal liver parenchymal absorbed dose 30 Gy; tumor absorbed dose >120 Gy; calculated activity 5.5 GBq ¹⁶⁶Ho-microspheres), (D) post-treatment ¹⁶⁶Ho-SPECT-CT and (E) MIP shows reproducible intrahepatic particle distribution, again in absence of extrahepatic depositions. During clinical follow-up, no further hypoglycemic episode at week 2 after treatment. (F) First radiological evaluation with arterial phase CECT 3 months after treatment, showing a PR according to RECIST 1.1 (largest lesion 31 mm; disappearance of multiple small metastases). (G) CECT 12 months after treatment showing continued regression of disease (largest lesion 24 mm). At that time, clinically no further hypoglycemic episodes, developed diabetes mellitus, and started metformin and additional insulin injections.