Abstract: Objective To explore the value of microRNAs (miR-550a-5p) in the diagnosis ofspinal bone metastases in non-small cell lung cancer (NSCLC), and to provide reference for clinical prevention and treatment. Methods Sixty-two NSCLC patients with the presence of spinal bonemetastasis and 44 NSCLC patients without spinal bone metastasis admitted to the Affiliated Hospital of Chengde Medical College from January 2019 to January 2023 were selected and included in the spinal bone metastasis group and the no spinal bone metastasis group, respectively, based on the confirmation of magnetic resonance imaging or CT examination. Serum miR-550a-5p, lung tumor markers [ carcinoembryonic antigen ( CEA ), cytokeratin-19 soluble fragment ( CYFRA21-1 ), neuron-specific enolase (NSE)], bone metabolism markers [type I collagen pyridine cross-linked amino-terminal peptide (NTx), bone transmutation alkaline phosphatase (BALP), Type I collagen carboxyl terminal peptide (ICTP)] were detected and compared between the two groups. The level of serum miR-550a-5p in NSCLC patients with different clinical characteristics was compared, and the association between the grade of NSCLC spine bone metastasis and the level of serum miR- 550a-5p was analyzed. The diagnostic value of serum miR-550a-5p in NSCLC spine bone metastasiswas analyzed by receiver operating characteristic curve (ROC). Results The levels of serum miR-550a-5p, CEA, NSE, CYFRA21-1, BALP, ICTP and NTx in the spinal bone metastasis groupwere higher than those in the non-spinal bone metastasis group (P < 0. 05). There were statisticallysignificant differences in the level of miR-550a-5p among NSCLC patients in spinal bone metastasis group with different tumor diameter, degree of differentiation, TNM stage, number of bone metastases, lymph node metastases, bone-related events and symptoms of bone pain (P< 0. 05). There weresignificant differences in the level of serum miR-550a-5p, NSE, BALP, CEA, ICTP, CYFRA21-1and NTx among NSCLC patients with different bone metastasis grades (P< 0. 05). The levels of serummiR-550a-5p, lung tumor markers and bone metabolism markers were increased with the increase of bone metastasis grade. Spearman correlation analysis showed that the level of serum miR-550a-5p was positively correlated with bone metastasis grade, and the levels of CEA, NSE, CYFRA21-1, BALP,ICTP and NTx (P< 0. 05). The AUC value of serum miR-550a-5p combined with lung tumor markers and bone metabolic markers was 0. 941 (95 % CI: 0. 878-0. 978) (P < 0. 05), which was higher than that of lung tumor markers combined with bone metabolic markers only [0. 902 (95 % CI:0. 829-0. 951)]. Conclusion miR-550a-5p has a high value in the diagnosis of spinal bone metastasisof NSCLC, and its level is closely related to bone metastasis grade, and level of lung tumor markers,and bone metabolic markers. Application of miR-550a-5p combined with lung tumor markers and bonemetabolic markers can improve the diagnostic value.

Key words: