Hans T. Chung

Introduction: Liver metastases are common in patients with neuroendocrine neoplasms. The role of stereotactic ablative radiotherapy (SABR) is not well understood in this population. Objective: The objective of this study was to evaluate the safety and efficacy of SABR in treating well-differentiated neuroendocrine liver metastases (WD-NELM). Methods: A retrospective review of patients with WD-NELM treated with SABR was conducted between January 2015 and July 2019. Demographic, treatment, and clinical/radiographic follow-up data were abstracted. RECIST 1.1 criteria were applied to each individual target to evaluate the response to treatment. Local control (LC) and progression-free survival (PFS) were determined using the Kaplan-Meier methodology. Toxicity was reported according to the CTCAE v5.0. Results: Twenty-five patients with a total of 53 liver metastases treated with SABR were identified. Most patients (68%) had midgut tumors, were grade 2 (80%), and had high-volume intrahepatic and/or extrahepatic disease (76%). The median number of liver metastases treated was 2, with a median size of 2.5 cm. The median radiation dose delivered was 50 Gy/5 fractions. The median follow-up was 14 months; 24 of the 25 patients were alive at the time of analysis. The objective response rate was 32%, with improvement or stability in 96% of lesions treated. The median time to best response was 9 months. The 1-year LC and PFS were 92 and 44%, respectively. No grade 3/4 acute or late toxicity was identified. Conclusions: Liver SABR is a safe and promising means of providing LC for WD-NELM. This treatment modality should be evaluated in selected patients in concert with strategies to manage systemic disease.