Purpose: Pathological evidence has continually supported the prognostic value of tumour-infiltrating T lymphocytes for several solid tumours across diverse patient cohorts. To investigate the clinical relevance of tumour-infiltrating memory T lymphocytes, we investigated relevant publications to identify the significance of memory tumour-infiltrating T lymphocytes (TILs) in predicting survival in cancer patients and analysed the influence of variations in the tumour stage and the infiltrated location thereon.
Methods: Relevant publications that assessed the clinical relevance of memory TILs to the patient's overall survival (OS) were investigated. Disease-free survival (DFS) was also evaluated where possible. Hazard ratios (HR) and 95% confidence intervals (CI) were assessed using a random-effects model. Heterogeneity was investigated with stratified analysis and I(2) statistics.
Results: In total, 16 relevant publications, including 4248 cancer patients, were analysed. In the pooled analysis, intra-tumour accumulation of memory TILs correlated positively with favourable clinical outcomes for both OS (pooled HR, 2.06; 95% CI, 1.76-2.40) and DFS (pooled HR, 2.31; 95% CI, 1.67-3.19). Various effects of the tumour stage and the anatomical region where the cells infiltrated were identified in survival prediction, using memory TILs.
Conclusions: Overall, infiltration of memory TILs can serve as a biomarker for survival prediction in cancer. Additional heterogeneous effects of the associated factors should be considered when categorizing high-risk patients.
Keywords: Cancer; memory T cells; prognosis; survival; tumour-infiltrating lymphocyte.