Neuroendocrine tumors (NETs) represent a spectrum of histologies which share the ability to secrete hormonal or vasoactive peptides.1 The most common NETs are carcinoid and pancreatic NETs. At the time of diagnosis, liver metastases are common and a negative predictor of survival.2 Furthermore, liver metastases can cause debilitating symptoms due to both mass effect and secretion of vasoactive peptides. A subset of these patients present with the classic carcinoid syndrome which includes diarrhea, flushing, bronchospasm, and valvular heart disease.3
Management of neuroendocrine liver metastases is optimized with a multidisciplinary approach that includes medical oncology, surgery, and interventional radiology. This allows for various treatment options to be discussed by subspecialists and a comprehensive treatment plan employed. Image-guided therapies, namely thermal ablation and transarterial embolization, are used both as an adjunct to surgery and when surgery is not a viable option.4 These techniques have been shown to be effective for both local tumor control and symptom relief.5 This chapter reviews the various image-guided therapies currently available for NET liver metastases with regard to technique, efficacy, and available outcomes data. In addition, emerging and novel image-guided therapies are also reviewed.
Ablation of neuroendocrine liver metastases is used for similar indications as surgical resection, typically in the setting of low tumor burden when surgical resection is not an attractive option.6 The 2012 National Comprehensive Cancer Network (NCCN) guidelines include ablation in the management of both carcinoid and pancreatic neuroendocrine liver metastases.7 Although surgery remains the gold standard, thermal ablation can be used for deep-seated lesions not amenable to wedge resection, when a nonsurgical minimally invasive procedure is preferred, or in patients who are poor surgical candidates.8
During thermal ablation procedures, one or more probes are advanced into target tumors under image guidance (Fig. 130-1). Once appropriate probe positioning is confirmed, thermal necrosis is induced in an elliptical zone surrounding the probe tip. The most common thermal ablative techniques for NET liver metastases are radiofrequency ablation (RFA) and microwave ablation (MWA), which have largely replaced cryoablation and percutaneous ethanol injection.9,10
A. Arterial phase contrast-enhanced CT demonstrates an arterially enhancing neuroendocrine liver metastasis (arrow). A hepatic cyst (arrowhead) is incidentally noted. B. CT image demonstrating tips of two microwave probes (arrow) centered within the neuroendocrine metastasis. C. Contrast-enhanced CT demonstrating postablation changes at the target lesion (arrow). A wide margin was created as the lesion was only visible on arterial phase imaging.
Clinical and Technical Considerations
Prior to the procedure date, a careful review of cross-sectional imaging such as computed tomography (CT) ...