Density of Tumor-Infiltrating FOXP3+T Cells as a Response Marker for Induction Chemoradiotherapy and a Potential Prognostic Factor in Patients Treated with Trimodality Therapy for Locally Advanced Non-Small Cell Lung Cancer

Purpose: To examine the relationship between the density of tumor-infiltrating T cell sub-populations and the pathological response to induction chemoradiotherapy (CRT) in patients with locally advanced NSCLC, and to assess the impact of T cell density on patient prognosis. Methods: A total of 64 patients with c-stages IIA-IIIB NSCLC who underwent induction CRT followed by R0 surgery were enrolled. Tumor-infiltrating T cells expressing either FOXP3 or CD8 were detected by immunohistochemical staining. Results: Mean numbers of tumor-infiltrating FOXP3+ T cells were 39.9 for patients with minor pathological responses (n = 9), 18.4 for those with major pathological responses (n = 25), and 12.9 for those with complete pathological responses (n = 30; P < 0.001). The number of CD8+ T cells was not associated with pathological responses. Patients with lower FOXP3+ T cell densities showed better survival, although the difference was not statistically significant. Conclusion: Our study demonstrated that the density of tumor-infiltrating FOXP3+ T cells indicated the degree of response for induction CRT and prognosis in patients treated with trimodality therapy for locally advanced NSCLC, suggesting that FOXP3+ T cells may be target for adjunct immunotherapy.