Abstract
Squamous cell carcinoma of the head and neck (SCCHN) has a high recurrence rate after (chemo) radiation therapy [(C)RT]. The relationship between the changing levels of immune checkpoint molecules and immune cells in pre-(C)RT tissues and locally recurrent tissues in the irradiated field, after (C)RT completion, is not known. This study aimed to assess the changes in these immune parameters between pre-(C)RT tissue and the same area after local recurrence post-(C)RT. We retrospectively reviewed 30 (C)RT-treated patients with SCCHN. We performed immunohistochemical analyses on these immune parameters using paired tissue samples obtained pre-(C)RT and at local recurrence sites post-(C)RT. No significant changes in immune parameters were found between the pre-(C)RT and locally recurrent tissues. An increased density of CD8+ tumor-infiltrating lymphocytes (TILs) showed a significantly positive correlation with PD-L expression on tumor cells (TC-PD-L1). Patients with increased TC-PD-L1 expression and CD8+TIL density showed favourable prognosis, and one of them showed a favourable response to nivolumab therapy. Our study shows a positive association between TC-PD-L1 upregulation and increased CD8+TIL density, and demonstrates that patients with these changes have a favourable survival outcome.