Bone metastases in lung carcinoids: current challenges in diagnosis and treatment -A systematic review of an unexplored issue.

Lung carcinoids (LCs) account for up to 25% of diagnosed NETs. Unlike gastroenteropancreatic NETs, LCs are more frequently associated with bone metastases (BMs), posing significant challenges due to their lower responsiveness to systemic treatments and the limited data on bone-modifying agents' efficacy in this setting. A systematic review on patients with BMs by LCs has been performed to assess the incidence of bone involvement, the clinical presentation and the current approach for both diagnosis and management. From the 61 selected articles, the incidence of BMs in LC patients was 17.2%, with a M/F ratio of 1.6. BMs were mostly symptomatic at diagnosis, while the 39% were detected only by imaging. Vertebrae were the most common site. Osteoblastic BMs were predominant BMs, while osteolitic BMs were more common in males. According on available data on nuclear medicine imaging, bone scintigraphy was positive in all cases. The most common treatments seemed to be radiotherapy and PRRT, while only two papers reported the effects of anti-resorptive agents in this setting. The median survival rate was 48,32 months, 24.9 months from the BMs detection. This systematic review focus on BMs in LCs, highlighting the challenges of diagnosis and therapy. First, our findings confirm the worse prognosis of LC patients with BMs vs. those without, pointing out the importance of the involvement of other specialists in managing these peculiar cases. Second, the need to evaluate the adequate techniques (including nuclear medicine) and timing of follow-up for these patients.