Bone Metastases in Patients with Neuroendocrine Neoplasm: Frequency and Clinical, Therapeutic, and Prognostic Relevance

Background: The incidence and prevalence of neuroendocrine neoplasms (NEN) are rising. In view of continuously improving imaging techniques, more than half of the patients present with distant metastases at initial diagnosis. An advanced disease stage negatively correlates with the 5-year survival rate. In stage IV disease, bone metastases (BM) are frequent, yet knowledge concerning their clinical or prognostic relevance is rare. This study presents a single-center experience on the frequency and management of BM in patients with gastroenteropancreatic NEN and lung carcinoids.

Methods: Between 2000 and June 2015, 327 of 677 patients treated in the European Neuroendocrine Tumor Society (ENETS) center in Marburg (Germany) presented with distant metastases (48.3%), including 85 patients (12.6%) with BM. Data of both groups were analyzed using descriptive statistics. Overall survival was assessed by Kaplan-Meier curves and compared by log-rank test.

Results: Median age in the BM group was 54.9 years, the small intestine and the pancreas being the most common primaries. 83.5% of the tumors were well and moderately differentiated (G1/G2). Nearly half of the patients with BM were symptomatic and suffered either from pain (42.4%) or had fractures (11.7%). Bisphosphonates were employed in almost two-thirds of the patients, radiation therapy in 25.9%. Overall survival was significantly inferior in patients with BM than in those with other distant metastases (p = 0.01; 49.0 vs. 100.8 months).

Conclusion: BM appear to have a significant clinical and prognostic impact. Further studies are needed to evaluate therapeutic approaches directed to the treatment of BM in particular for asymptomatic patients.