Prognostic impact of bone metastases detected by 18F-DOPA PET in patients with metastatic midgut neuroendocrine tumors

Bone metastases (BM) may influence negatively the prognosis of midgut neuroendocrine tumors (NET). The diagnostic sensitivity of 18F-DOPA PET for midgut NET and associated metastases is high. This study aimed to assess the prognostic impact of BM detected by 18F-DOPA PET in metastatic midgut NET. All patients with a metastatic midgut NET, who underwent a 18F-DOPA PET between June 2011 and June 2018, were included. BM were defined following imaging criteria and were classified as poly-BM or oligo-BM, according to their number (< 5 or ≥ 5, respectively). The variables associated with the presence of BM were evaluated by logistic regression. The factors associated with overall survival were explored by Cox regression models. Among 155 patients included, 46 had BM (29.7%). A carcinoid syndrome (OR 2.96, p = 0.009) and ≥ 3 extra-skeletal metastatic organs (OR 4.99, p = 0.002) were independently associated with the presence of BM. BM were mainly osteoblastic (78%), rarely symptomatic (8.9%), and had a short-term therapeutic impact for 3 patients (6.5%). The presence of BM (HR 2.67, p = 0.034), older age (HR 1.07, p = 0.016), and higher Ki67 (HR 1.09, p = 0.025) were independent prognostic factors. Unlike poly-BM (HR 1.92, p = 0.007), oligo-BM was not a poor prognosis factor (HR 0.77, p = 0.699) compared to the group without BM. 18F-DOPA PET frequently detects BM in patients with metastatic midgut NET. BM have a negative prognostic impact, especially poly-BM. Conversely, oligo-BM do not influence the prognosis and may not impact therapeutic decisions. • 18 F-DOPA PET detected bone metastases in 46 (29.7%) of 155 patients with metastatic midgut neuroendocrine tumors. • Bone metastases have a negative prognostic impact in metastatic midgut neuroendocrine tumors. • Bone oligo-metastases (< 5) do not influence the prognosis and may not impact therapeutic decisions.