Increased CD8+CD28+T cells independently predict better early response to stereotactic ablative radiotherapy in patients with lung metastases from non-small cell lung cancer

Background: Stereotactic ablative radiotherapy (SABR) shows a remarkable local control of non-small cell lung cancer (NSCLC) metastases, partially as a result of host immune status. However, the predictors of immune cells for tumor response after SABR are unknown. To that effect, we investigated the ability of pre-SABR immune cells in peripheral blood to predict early tumor response to SABR in patients with lung metastases from NSCLC. Methods: This study included 70 patients with lung metastases from NSCLC who were undergoing SABR. We evaluated the early tumor response 1 month and 6 months after SABR in these patients following RECIST 1.1 guidelines. Pre-SABR peripheral CD8+ T cell count, CD8+CD28+ T-cell count, CD8+CD28-T-cell count, CD4+ T-cell count, and Treg-cell count were measured using flow cytometry. Results: Increased CD8+ CD28+ T-cell counts (14.43 +/- 0.65 vs. 10.21 +/- 0.66; P = 0.001) and CD4/Treg ratio (16.96 +/- 1.76 vs. 11.91 +/- 0.74; P = 0.011) were noted in 1-month responsive patients, compared with non-responsive patients. In univariate logistic analyses, high CD8+CD28+ T-cell counts (OR 0.12, 95% CI 0.03-0.48; P = 0.003), CD4/Treg ratio (OR 0.24, 95% CI 0.06-0.90; P = 0.035), and BED10 (OR 0.91, 95% CI 0.84-0.99; P = 0.032) predicted a 1-month tumor response to SABR. According to multivariate logistic analyses, the CD8+ CD28+ T-cell count predicted a 1-month tumor response to SABR (OR 0.19, 95% CI 0.04-0.90; P = 0.037) independently. Furthermore, we confirmed the independent predictive value of the CD8+CD28+ T-cell count in predicting tumor response to SABR in 41 patients 6 months after treatment (OR 0.08, 95% CI 0.01-0.85; P = 0.039). Conclusions: A pre-SABR CD8+CD28+ T-cell count could predict early tumor response to SABR in patients with lung metastases from NSCLC. Larger, independently prospective analyses are warranted to verify our findings.