Prognostic importance of tumour‐infiltrating memory T cells in oesophageal squamous cell carcinoma

Summary Memory T cells survive for many months and years and are critically important for host defence in humans. In tumour immunity, they have been also suggested to play a significant role in tumour progression and metastasis. However, the role of memory T cells in actual human cancer remains largely unknown. In this study, the clinical importance of tumour‐infiltrating CD45RO + memory T cells was investigated in human oesophageal squamous cell carcinoma (OSCC). CD45RO + T cells were evaluated by immunohistochemistry in primary OSCC tumours from 105 patients. Patients were classified into two groups as CD45RO +hi or CD45RO +lo based on the number of cells stained positively for CD45RO. No significant difference was observed between CD45RO status and several clinicopathological prognostic factors. However, the postoperative overall and disease‐free survival for CD45RO +hi patients was significantly better than for CD45RO +lo patients. Furthermore, there were significant correlations of CD45RO status in the primary tumour with postoperative lymph node and pulmonary recurrence, suggesting that memory T cells may control postoperative metastatic recurrence. Most importantly, CD45RO + memory T cell status has a significant prognostic value for OSCC independently of conventional tumour–node–metastasis (TNM) classification. Our study may provide a rationale for developing a novel immunotherapy in intentional induction of memory T cells for the treatment of oesophageal cancer.