Peripheral CD8⁺ T cell proliferation is prognostic for patients with advanced thoracic malignancies

There is a complex interplay between the immune system and a developing tumor that is manifest in the way that the balance of T cell subsets in the local tumor environment reflects clinical outcome. Tumor infiltration by CD8⁺ T cells and regulatory T cells (Treg) is associated with improved and reduced survival, respectively, in many cancer types. However, little is known of the prognostic value of immunological parameters measured in peripheral blood. In this study, peripheral CD8⁺ T cells and Treg from 43 patients with malignant mesothelioma or advanced non-small-cell lung cancer scheduled to commence palliative chemotherapy were assessed by flow cytometry and evaluated for association with patient survival. Patients had a higher proportion of peripheral Treg, proliferating CD8⁺ T cells and CD8⁺ T cells with an activated effector phenotype compared with age-matched healthy controls. Higher proportions of Treg and proliferating CD8⁺ T cells were both associated with poor survival in univariate analyses (hazard ratio [HR] 3.81, 95 % CI 1.69–8.57; p < 0.01 and HR 2.86, 95 % CI 1.26–6.50; p < 0.05, respectively). CD8⁺ T cell proliferation was independently predictive of reduced survival in multivariate analysis (HR 2.58, 95 % CI 1.01–6.61; p < 0.05). These findings suggest that peripheral CD8⁺ T cell proliferation can be a useful prognostic marker in patients with thoracic malignancies planned for palliative chemotherapy.