Risk Stratification for the Prediction of Skeletal-Related Events in Patients With Bone Metastases From Non-small Cell Lung Cancer

Skeletal-related events (SREs) frequently occur in patients with bone metastases from non-small cell lung cancer (NSCLC). This study aimed to identify risk factors for SREs in patients with NSCLC. Based on these factors, we also aimed to stratify patients into subgroups to facilitate the assessment of SRE risk. This retrospective analysis used medical records of 139 patients with NSCLC bone metastases who received treatment at our institution between 2011 and 2014. The incidence of SREs was assessed, and SRE-free survival was analyzed using the Kaplan-Meier method. Clinical information collected at registration was assessed to identify factors associated with the onset of SREs within six months. Univariate analysis was performed using Fisher's exact test, and multivariate analysis was performed using Cox regression. Of the 139 patients, 36 (26%) developed SREs after registration. The SRE-free survival rates were 80% and 64% at 6 and 12 months, respectively. The univariate and multivariate analyses revealed that the absence of epidermal growth factor receptor (EGFR) mutations or anaplastic lymphoma kinase (ALK) rearrangement (hazard ratio (HR): 4.51, 95% confidence interval (CI): 1.32-15.7, p = 0.017) and a lactate dehydrogenase (LDH) level ≥400 U/L (HR: 8.08, 95% CI: 1.78-36.6, p = 0.0067) were risk factors for SRE presentation within six months. Patients were classified into the following three subgroups: with EGFR mutation or ALK rearrangement and LDH level <400 U/L; without EGFR mutation or ALK rearrangement and LDH level <400 U/L; with/without EGFR mutation or ALK rearrangement and LDH level ≥400 U/L. The corresponding six-month SRE-free survival rates were 92%, 69%, and 34%, respectively, showing significant differences (p < 0.001). Close monitoring is recommended for patients with LDH levels ≥400 U/L in daily clinical practice, particularly with the help of the proficiency of orthopedic and radiological experts, to prevent complications such as pathological fractures and paraplegia.