Consolidative versus salvage stereotactic ablative radiotherapy to the primary lung tumor in stage IV non-small cell lung cancer.

Background: The optimal timing of stereotactic ablative radiotherapy (SABR) to the primary lung tumor-whether delivered as consolidative therapy or as salvage therapy -remains undefined in stage IV non-small cell lung cancer (NSCLC). This study compared the efficacy and safety of these two strategies. Methods: We retrospectively analyzed 90 patients with stage IV NSCLC who received primary lung tumor SABR between October 2020 and November 2025. Patients were categorized into consolidative SABR (n=64) and salvage SABR (n=26). Endpoints included local progression-free survival (LPFS), distant metastasis-free survival (DMFS), and overall survival (OS). Competing risk analyses and multivariable Cox regression were applied. Sensitivity analyses excluding Results: Median follow-up was 38.8 months. Consolidative and salvage SABR showed comparable LPFS (1-year rate: 93.8% vs. 84.6%; P = 0.848), DMFS (75.0% vs. 61.5%; P = 0.806), and OS (96.2% vs. 77.6%; P = 0.775). In multivariable analysis, Conclusions: In stage IV NSCLC, consolidative and salvage SABR to the primary tumor achieved comparable local control, distant progression, and overall survival, with analogous safety profiles. These findings indicate that the timing of primary tumor ablation does not independently dictate long-term oncologic outcomes in the context of effective modern systemic therapy. The decision between early consolidation and deferred salvage may be guided by tumor anatomy, anticipated toxicity, and patient preference rather than by anticipated survival advantages. Future prospective trials should adopt non-inferiority frameworks and prioritize composite endpoints-including toxicity, quality of life, and cost-effectiveness-to definitively optimize patient selection and sequencing for this strategy.