Head and neck squamous cell cancers (HNSSC) generate an immune-suppressive micro-environment by a specific pattern of tumour infiltrating inflammatory cells. The aim of our study was to evaluate the impact of radiochemotherapy on the numbers and composition of inflammatory cells and its influence on outcome. Fifty-eight patients suffering from oral cavity cancer were studied, whose therapy consisted of concurrent radiochemotherapy followed by surgery. Numbers and ratios of tumour infiltrating inflammatory cells were compared prior to and after radiochemotherapy. Intraepithelial and stromal location of tumour infiltrating inflammatory cells was analysed separately. Infiltration of CD3(+), CD4(+), CD25(+), FoxP3(+), CD8(+), Granzyme B(+), CD20(+) and CD68(+) cells predominated in the peritumoural stromal compartment, whereas CD1a(+) dendritic cells were found more frequently in the intraepithelial compartment. Neoadjuvant treatment was associated with a general decrease of tumour infiltrating inflammatory cells in both compartments. The CD8(+) and Granzyme B(+) cytotoxic cells decreased only slightly after RCT. In contrast, the decrease of FoxP3(+) regulatory T cells was more pronounced and the cytotoxic T-cell/FoxP3(+) ratio increased 2- to 3-fold in both compartments, respectively. Patients with high cytotoxic cell numbers, high dendritic cell numbers and a high ratio of cytotoxic cells to regulatory T cells had a better disease free survival. Concurrent radiochemotherapy of oral squamous cell carcinoma was shown to drive the composition of inflammatory cells in a direction which is supposed to be prognostically favourable.
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