Outcome of patients with lung cancer treated with stereotactic body radiotherapy for bone oligometastases - a European multicenter cohort study

Abstract Introduction Metastasis-directed radiotherapy is of increasing importance in the multidisciplinary management of oligometastatic non-small cell lung cancer (NSCLC), but outcome patterns for stereotactic body radiotherapy (SBRT) of bone oligometastases (BoM) remain insufficiently defined. We aimed to determine oncological outcomes and prognostic factors of SBRT for BoM of NSCLC. Materials and methods Patients with NSCLC treated with SBRT for < 5 BoM between 2010 and 2024 at 15 European cancer centers were retrospectively analyzed. Outcomes included freedom from local recurrence (FFLR), progression-free survival (PFS), overall survival (OS), and adverse events. Results With a median follow-up of 14 months (IQR: 7–24 months), 85 patients with 111 treated BoM were analyzed. The 2-year FFLR was 87.2% (95%-CI: 73.3%-94.1%). The 1-/2-year PFS for singular BoM was 60.1% (CI: 44.6%-72.5%)/ 39.9% (CI: 24.6%-54.8%), while for 2–3 BoM they amounted to 10.2% (95%-CI: 0.6%-35.8%) and 0%. In multivariable analysis, less favorable outcome for OS and PFS was associated with larger BoM (HR 1.003; p < 0.01 and HR 1.005, p < 0.001) and increased number of treated BoM (HR 1.72; p = 0.03 and HR 1.93; p < 0.01). Treatment was well tolerated, with fracture rates of 5.4% and no grade 4 and 5 adverse events. Conclusion This multicenter cohort analysis revealed that SBRT of BoM from NSCLC appears to be an effective and well-tolerated treatment. Presence of singular BoM was a favorable prognostic factor. Prospective studies are needed to confirm these findings and to determine the role of SBRT in the multidisciplinary management of oligometastases.