Peripheral CD8+ T Cell Dynamics and Clinical Outcomes in Metastatic Non-Small Cell Lung Cancer Following Bronchoscopic Cryotherapy and Pembrolizumab-Based Therapy

Background: Bronchoscopic cryotherapy may enhance anti-tumor immunity and improve the effect of immune checkpoint blockade, but CD8+ T cell dynamics after cryotherapy combined with pembrolizumab-based therapy in metastatic non-small cell lung cancer (NSCLC) remain insufficiently characterized. Methods: In this prospective, exploratory, randomized, controlled, single-center study, metastatic NSCLC patients were assigned to bronchoscopic cryotherapy performed 7 ± 1 days before first-line pembrolizumab-based therapy or to standard treatment alone. Peripheral blood mononuclear cells were analyzed by flow cytometry at baseline, week 3, and week 6. CD8+ T cell subsets defined by CD45RO, CD28, granzyme B (GzB), IFNγ, Ki-67, and PD-1 were evaluated in relation to treatment group, radiologic response, progression-free survival (PFS), and overall survival (OS). Results: Flow cytometry was performed in 76 patients, including 34 in the cryotherapy group and 42 in the control group. Cryotherapy was associated with a treatment-specific increase in circulating GzB+ CD8+ T cells by week 6. In contrast, Ki-67+ CD8+ and GzB+Ki-67+ cells increased in both treatment groups, suggesting that early peripheral CD8+ proliferation was largely shared across pembrolizumab-based therapy. Radiologic responders demonstrated more sustained proliferative CD8+ dynamics, most consistently reflected by increased CD28+ Ki-67+ cells. In exploratory landmark survival analyses, a higher week-3-to-baseline GzB+ Ki-67+ CD8+ ratio showed a hypothesis-generating association with longer PFS and OS. Conclusions: In metastatic NSCLC patients receiving first-line pembrolizumab-based therapy, the addition of bronchoscopic cryotherapy was associated with peripheral CD8+ T cell remodeling toward enhanced cytotoxic activity. Proliferative CD8+ T cell changes were associated with radiologic response and better survival. These findings support bronchoscopic cryotherapy as a potential immune-modulating adjunct and warrant validation in larger studies.