High Peripheral Regulatory T Cells Independently Predict Poor Outcomes for Stereotactic Ablative Radiotherapy of Pulmonary Recurrence-Based Oligometastatic Non-Small Cell Lung Cancer

Abstract

We aimed to evaluate the prognostic value of peripheral immune cells in oligometastatic non-small cell lung cancer (NSCLC) patients who are treated with stereotactic ablative radiotherapy (SABR). We enrolled 63 patients with pulmonary recurrence-based oligometastatic NSCLC; all patients’ metastases had been treated with SABR. Peripheral regulatory T cells (CD4+CD25+CD127low), B cells, NK cells, γδT cells, CD8+CD28+ T cells, and CD8+CD28- T cells were evaluated by flow cytometry. Prognostic values of factors were evaluated by Cox proportional hazards regression. The median follow-up time was 19.1 months. Estimated overall survival (OS) rates at 1, 2, and 3 years were 84.3%, 63.4%, and 44.0%. Estimated progression-free survival (PFS) rates at 1, 2, and 3 years were 55.2%, 30.9%, and 25.7%. Patients with high regulatory T cells (Treg) showed decreased OS and PFS, compared with those with low Treg cells (OS: 16.1 months vs. not reached, P = 0.006; PFS: 11.0 vs. 21.7 months, P = 0.006). Treg level is an independent prognostic factor for both OS and PFS in patients with pulmonary recurrence-based oligometastatic NSCLC who were treated with SABR in multivariate analyses (HR = 2.68, 95% CI: 1.05-6.85, P = 0.038, and HR = 2.35, 95% CI: 1.21-4.54, P = 0.011, respectively). Peripheral Treg level revealed independent prognostic value in patients with pulmonary recurrence-based oligometastatic NSCLC, in which patients were treated with SABR for all metastases. Additional treatments may require combination with SABR following selection of oligometastatic NSCLC patients with poor outcomes.