CLINICAL PRESENTATION OF BONE METASTASES IN NEUROENDOCRINE TUMORS: A RETROSPECTIVE COHORT STUDY

: Bone metastases (BMs) are rare and late event in patients with neuroendocrine tumors (NETs). The aim of our study was to investigate clinical presentation and outcome of BMs in a large cohort of patients with NETs. A retrospective study was performed at two referral centers of Northern Italy (IRCCS Humanitas Research Hospital in Milan and S. Maria della Misericordia University Hospital in Udine). Three-hundred-fifty-two consecutive patients with either gastroenteropancreatic or non gastroenteropancreatic NETs were included: 52 patients with synchronous or metachronous BMs (BM-positive) and 300 patients with metastatic disease without BMs (BM-negative). Patients with BMs showed a higher prevalence of smoking habit (41.2% vs 21.8%, p-value=0.004) and carcinoid syndrome (28.8% vs 5.7%, p-value<0.001), as compared to patients without BMs. In addition, higher levels of chromogranin A (p-value=0.001), urinary 5-hydroxyindoleacetic acid (p-value<0.001), parathyroid hormone (p-value=0.022) and alkaline phosphatase (p-value=0.018) were found, as compared to BM-negative group. Patients with BMs had more frequently a primary lung NET, compared to the BM-negative group (19.2% vs 0.7%, p-value=0.001) and grade G2 or G3 gastroenteropancreatic tumors (p-value<0.001), as compared to BM-negative group. During a median follow-up of 4.2 years, a higher mortality rate was registered in the BM-positive group as compared to BM-negative group (42.3% vs 4.0%, p-value=0.001). BMs were more common in patients with lung NETs, G2-G3 grade and in those with carcinoid syndrome. BMs affected patients' prognosis, highlighting the importance of investigating and managing this condition in patients with NETs.