Impact on symptoms and survival of bone metastases in patients with small-intestinal neuroendocrine tumours

We aimed to assess the symptoms and impact on overall survival (OS) from bone metastases (BM) diagnosed on Gallium-68-labelled DOTA tyrosine octreotide positron emission tomography with computed tomography (⁶⁸Ga-DOTATOC-PET/CT) in patients with well-differentiated small intestinal neuroendocrine tumours (Si-NETs). Patients with well-differentiated Si-NETs, who underwent ⁶⁸Ga-DOTATOC-PET/CT between 2010 and 2023 at two tertiary referral centres in Sweden, were included. Their number of BM, ≤5 BM versus >5 BM, symptoms and need for analgesics were recorded. To further assess the impact of BM on OS, we used a control group of age- and sex-matched Si-NET patients with liver metastases (Stage IV disease) but without BM. The prevalence of BM in Si-NET patients was 23% (175/753); among these, complete clinical data were available in 138 patients. Synchronous BM were found in 33% (46/138). Sixty-one patients (44%) showed >5 BM at the time of BM detection. Fractures were diagnosed in 4% (n = 6) and 14% (n = 20) needed analgesics for BM-associated pain. In univariable analysis, patients with >5 BM experienced shorter OS from the time of BM detection compared to those with ≤5 BM (18 months vs. 75 months, p < .001). Among patients with Stage IV disease with and without BM, OS was shorter in patients with BM compared to patients with no BM (72 months vs. 288 months, p = .002). In multivariable analysis of patients with BM, higher Ki-67% (hazard ratio [HR] = 1.06, p = .007), older age (HR = 1.07, p < .01), presence of >5 BM (HR = 1.93, p = .021) and synchronous BM (HR = 2.14, p = .016) were identified as independent prognostic factors for shorter OS. In the matched cohort of patients with Stage IV disease with and without BM, presence of BM (HR = 1.94, p = .009), age at diagnosis of Stage IV (HR = 1.08, p < .001) and locoregional surgical resection (HR = 0.47, p = .015) were independent prognostic factors for survival. BM are detected in approximately 25% of Si-NET patients subjected to ⁶⁸Ga-DOTATOC-PET/CT. Pain occurs in approximately 14% and fractures in 4%. The presence of BM among Stage IV patients, the extent of bone disease (>5 BM) and synchronous BM are independent prognostic factors for shorter OS.