Efficacy and Time-Dependent Pattern of Consolidation Immunotherapy in Stage III Non-Small Cell Lung Cancer After Induction Chemoimmunotherapy and Radiotherapy: A Dual-Center Retrospective Cohort Study

Background/Objectives: The efficacy and time-dependent pattern of consolidation immunotherapy after induction chemoimmunotherapy and radiotherapy remain unclear in unresectable stage III non-small cell lung cancer (NSCLC). This study evaluated the efficacy and temporal pattern of consolidation immunotherapy in this population. Methods: This dual-center retrospective cohort study included patients with unresectable stage III NSCLC who achieved disease control after induction chemoimmunotherapy followed by definitive radiotherapy. To reduce potential immortal time bias, only patients who remained alive and progression-free within 2 months after radiotherapy were included. Patients were grouped according to receipt of consolidation immunotherapy. Survival outcomes were analyzed using stabilized inverse probability of treatment weighting, multivariable Cox regression, sequential landmark Cox analysis, and landmark restricted mean survival time analysis. Results: Among 170 eligible patients, 65 received consolidation immunotherapy and 105 did not. After a median follow-up of 33 months, consolidation immunotherapy was associated with longer PFS (hazard ratio [HR]: 0.52, 95% confidence interval [CI]: 0.35–0.78, p = 0.001) and OS (HR: 0.35, 95% CI: 0.18–0.65, p < 0.001). These benefits remained significant after weighting, and multivariable analysis identified consolidation immunotherapy as an independent predictor of improved PFS. Exploratory sequential landmark Cox and restricted mean survival time analyses suggested that the survival benefit was more evident during the early treatment period, particularly around 8–10 months. Conclusions: Consolidation immunotherapy was associated with improved survival, and its benefit appeared more evident during the early treatment period, particularly around 8–10 months. The optimal treatment duration requires further prospective validation.