The prognostic role of circulating CD8(+) T cell proliferation in patients with untreated extensive stage small cell lung cancer

BACKGROUND: Immunosuppression caused by tumorigenesis may promote tumor progress and invasion. Here, we investigated whether the characteristics of circulating T lymphocyte subtypes in patients with extensive small cell lung cancer (ED-SCLC) can be used as an alternative marker of tumor progression. METHODS: This study included 36 newly diagnosed ED-SCLC patients before treatment and the patients were followed up. 22 age and sex-matched healthy volunteers were selected as control. The percentages and proliferation potential of T lymphocyte subpopulations from peripheral blood were measured. RESULTS: CD4(+) CD25(+) Foxp3(+) regulatory T cells (Tregs) were elevated in ED-SCLC patients compared with healthy controls (p = 0.0083). In contrast, the percentages of CD3(+) and CD3(+)CD4(+) T cells were significantly lower in SCLC patients (p < 0.001; p = 0.0014). The proliferation (%divided) of CD8(+) T cells of SCLC patients was suppressed compared with healthy controls (p = 0.0058), but not of CD4(+) T cells (p = 0.1611). Multivariate analyses showed that the %divided of CD8(+) T cells is an independent predictor for PFS (HR: 4.342, 95% CI 1.324–14.245; p = 0.015). The percentages of peripheral Tregs and the degree of chemotherapy or radiotherapy induced lymphopenia negatively correlated with the proliferation of CD8(+) T cells (p = 0.0225, r = − 0.379; p = 0.0003, r = − 0.464). CONCLUSION: The present study indicates that SCLC patients have impaired immunity in peripheral blood, and the proliferation potential of circulating CD8(+) T cells is a significant predicator for PFS.