Ablative Dose Y90 Radiation Segmentectomy for Treatment of Neuroendocrine Liver Metastases.

Purpose: To assess the safety and efficacy of Y90 radiation segmentectomy (RS) for neuroendocrine tumor liver metastases (NELMs).

Materials and methods: This single-institution retrospective study included 18 patients with 23 liver tumors not amenable to resection or ablation, who underwent RS between 2009 and 2021. Tumor grades by Ki-67/mitotic indices were Grade I (n=9/23, 39%), Grade II (n=10/23, 45%) and Grade III (n=4/23, 17%). Eleven patients (61%) were previously treated with somatostatin analogs, five (28%) with chemotherapy, and two (11%) with peptide receptor radionuclide therapy. Safety was assessed with pre/post liver chemistries, blood counts and clinical adverse events (AEs) using National Cancer Institute Common Terminology Criteria for AEs v5.0. Tumor response was assessed per Response Evaluation Criteria in Solid Tumors 1.1 and modified RECIST criteria. Kaplan-Meier analysis was used to estimate median overall survival (OS), progression-free survival (PFS), and time to progression (TTP) from the date of Y90.

Results: Median follow-up was 31.9 months. Grade 1 fatigue was observed in 13/18 patients (72%), with 1/18 patient (6%) experiencing grade 3 fatigue. Three patients (17%) exhibited grade 3 lymphopenia. No other grade 3 or any grade 4 AE was observed. Tumor objective response was achieved in 83% of patients by RECIST size criteria and 100% by mRECIST enhancement criteria. Median OS was 69.4 months (95% CI, 23.1-99.4) and median PFS was 12.2 months (95% CI, 4.6-28.8). Median overall TTP was 13.0 months (95% CI, 4.6-45.1), with median treated tumor TTP not reached.

Conclusion: Y90 RS demonstrates high rates of antitumor response with a favorable toxicity profile and durable OS in the treatment of NELMs.