Tumor-infiltrating memory T-lymphocytes for prognostic prediction in cancer patients: a meta-analysis

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.

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.

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.

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.