Selective internal radiation therapy for neuroendocrine liver metastases: efficacy, safety and prognostic factors. A retrospective single institution study

Background and study aims: Selective internal radiation therapy (SIRT) has shown good results in unresectable liver metastases from neuroendocrine neoplasms (NELM) with a high disease control rate (DCR) reported. The aims of the study is to assess retrospectively the efficacy and safety of 10y of SIRT for NELM.

Patients and methods: Primary endpoint was objective response rate (ORR) and DCR by RECIST 1.1 at 2, 4 and 12 months (m). Secondary endpoints were overall survival (OS), liver progressionfree survival (liver-PFS), clinical response (NEN-related symptoms improvement) and safety.

Results: 50 consecutive patients with NELM who got SIRT from 2011 to 2021 in one center. The two major NEN primary sites were pancreas (46%) and small intestine (36%). Histological NEN grades were 10%, 46% and 44% for grades 1, 2 and 3 respectively. ORR and DCR were 16% and 80% at 2m, 22% and 92% at 4m and 32% and 82% at 12m. Survival rates at 1 and 2 y were 76% and 72% respectively. Prognostic factors for OS and liver-PFS were NEN histological grade (3 vs 1+2) (hazard ratio (HR) for OS: 4.33 [1.8-10.6], for liver-PFS: 3.91 [1.3-11.4]), and early (2m) DCR (HR for OS: 0.14 [0.1-0.4], for liver-PFS: 0.016 [0.003-0.08]). Clinical response occurred in 7 of the 10 symptomatic patients. One patient died from radioembolization-induced liver disease.

Conclusion: SIRT showed efficacy in NELM pts, with a high DCR and an good safety profile. G1-2 grade and early DCR were associated with a better OS and liver-PFS.

Keywords: SIRT, neuroendocrine tumours, effectiveness, outcomes, liver metastases.