CD45RO(+) Memory T Lymphocytes--a Candidate Marker for TNM-Immunoscore in Squamous Non-Small Cell Lung Cancer

Tumor-infiltrating lymphocytes (TILs) are vital in limiting cancer progression and may supplement the TNM classification. CD45RO(+) memory TILs show major prognostic impact in various malignancies but have not been extensively explored in non-small cell lung cancer (NSCLC). In this study, we aimed to evaluate their potential in a NSCLC TNM-Immunoscore. Tissue microarrays were constructed from tumor tissue samples from two cohorts including in total 536 patients (University Hospital of North Norway, n = 285; Nordland Hospital, n = 251) with primary resected stage I to IIIA NSCLC. The density of CD45RO(+) and CD8(+) TILs in tumor epithelial and stromal compartments of the tumors was evaluated by immunohistochemistry. In univariate analyses, intraepithelial CD45RO(+) TIL density (T-CD45RO) was a significant prognostic factor for disease-specific survival (P = .007), limited to the squamous cell carcinoma (SCC) histology subgroup (P < .001), where it was significant in both cohorts (University Hospital of North Norway, P = .003; Nordland Hospital, P = .022). Combining T-CD45RO and stromal CD8(+) TIL density (S-CD8) increased the prognostic impact in SCC (P < .001) and showed a significant impact within all pathological stages (I, P = .025; II, P < .001; III, P = .001). In the multivariate analysis, T-CD45RO was an independent positive prognostic factor for SCC (hazard ratio 2.65, 95% confidence interval 1.64-4.28, P < .001), and in combination with S-CD8, the prognostic impact increased vastly (high + high versus low + low: hazard ratio 6.50, 95% confidence interval 3.54-11.91, P < .001). In conclusion, T-CD45RO was an independent prognostic factor for SCC NSCLC. When combined with S-CD8, the prognostic impact increased and was significant within each pathological stage. We propose CD45RO as a candidate marker for TNM-Immunoscore in SCC NSCLC.