To analyze the efficacy of tislelizumab following stereotactic body radiation therapy (SBRT) in patients with metastatic non-small-cell lung cancer (mNSCLC).

Retrospective data were collected from 112 mNSCLC patients treated at our hospital between January 2021 and December 2024. Patients were divided into control group 59 cases and observation group 53 cases based on treatment regimens. Chemotherapy was initiated 14 days after SBRT. The control group received carboplatin AUC 5~6 + paclitaxel 175 mg/m² or pemetrexed 500 mg/m² intravenously on day 1, repeated every 3 weeks until disease progression or intolerable toxicity. The observation group received tislelizumab 200 mg intravenously every 3 weeks. Clinical efficacy, tumor marker levels, T lymphocyte subsets and cytokine levels, pulmonary function, CT findings, adverse events, and survival outcomes were compared between the two groups.

No significant differences were observed in objective response rate (ORR), disease control rate (DCR), or incidence of adverse events between the observation and control groups (P>0.05). After treatment, the observation group showed lower levels of carcinoembryonic antigen (CEA) (14.93±3.48) ng/ml, cytokeratin 19 fragment antigen21-1 (CYFRA21-1) (8.17±3.03) ng/ml, carbohydrate antigen 50 (CA50) (10.85±2.96) U/ml, regulatory T cells (Treg) (2.39±0.68)%, interleukin-5(IL-5) (20.74±2.76) pg/ml, arterial phase normalized iodine concentrations (NICAP) 0.17±0.05, venous phase normalized iodine concentrations (NICVP) 0.44±0.11, and slope of spectral Hu curve (s-SHC) 1.48±0.33 compared to the control group (16.54±3.29) ng/ml, (9.62±3.28) ng/ml, (12.33±3.07) U/ml, (2.78±0.76)%, (22.13±3.49) pg/ml, (0.20±0.06), (0.49±0.12), and ( 1.62±0.29) (P<0.05). The observation group exhibited higher CD4⁺ T cells (CD4⁺ )/ CD8⁺ T cells (CD8⁺ ) 0.71±0.16, interferon-γ (IFN-γ) (54.26±6.51) pg/ml, forced expiratory volume in one second (FEV₁) (2.38±0.32) L, peak expiratory flow (PEF) (2.62±0.46) L/s, maximal mid-expiratory flow curve (MMEF) (2.12±0.34) L/s, median progression-free survival (PFS) 14.3 months, survival rate 47.17%, and median overall survival (OS) 24.6 months compared to the control group 0.64±0.14, (51.32±6.48) pg/ml, (2.22±0.29) L, (2.43±0.39) L/s, (1.96±0.31) L/s, 11.0 months, 28.81%, and 20.5 months (P<0.05).

Tislelizumab after SBRT reduces tumor marker levels, modulates immune function, improves pulmonary function, and enhances survival outcomes in mNSCLC patients with a favorable safety profile.