To Örebro University

Introduction: The prevalence of Bone metastases (BM) in small intestinal neuroendocrine tumours (Si-NET) ranges from 6-23 % and has increased due to new radiology modalities. The aim of our study was to evaluate the overall survival (OS) and the associated symptoms, in particular bone-related pain and fractures in Si-NETpatients with BM.

Method: Retrospective cohort study between 2010-2023 including 138 Si-NET patients with BM detected at 68 Gallium-DOTATOC-PET/CT, treated and followed at Uppsala University Hospital in Sweden. Patients were grouped into two groups according to their number of BM; ≤ BM or > 5 BM. We also included 77 sex and age matched control patients with Si-NET and liver metastases, matched to 77 Si-NET patients with BM and liver metastases.

Result: Of 138 patients, 14 % were treated for BM related pain and 4% patients had a fracture related to Si-NET BM. OS of patients with >5 BM was shorter compared to patients with ≤5 BM (5-year OS 21 % vs 58%; p-=0.028). Concurrent carcinoid heart disease was present in 22% of Si-NET patients with BM, more frequently found inthose with > 10 BM (40%). In the case-control group, OS was 30 % in the case group with BM compared to the control group 64 % (p-value <0.01).

Discussion: Fractures are rare and bone-related pain treatment is needed in 14 % of patients with BM. Presence of > 5 BM is associated with shorter OS and increased risk of carcinoid heart disease. The presence of BM also impair the prognosis, compared to control patients with comparable abdominal metastastic burden.