Objective measurement and clinical significance of TILs in non-small cell lung cancer

Background: Tumor-infiltrating lymphocytes (TILs) are usually measured using subjective methods. Studies suggest that TIL subtypes have independent roles in cancer and that they could support the use of novel immunostimulatory therapies. We simultaneously measured TIL subtypes in non-small cell lung cancer (NSCLC) samples using objective methods and determined their relationship with clinico-pathologic characteristics and survival.

Methods: Using multiplexed quantitative fluorescence (QIF), we measured the levels of CD3, CD8, and CD20 in 552 NSCLC from two independent collections represented in tissue microarrays (YTMA79, n = 202 and YTMA140, n = 350). The level of TILs was obtained in different tumor compartments using cytokeratin stain to define tumor cells and 4',6-Diamidino-2-Phenylindole. Association of TILs with clinical parameters was determined using univariate and multivariable analyses. All statistical tests were two-sided.

Results: In both NSCLC collections there was a low correlation between the three TIL markers (linear regression coefficients (R(2)) = 0.19-0.22, P < .001 for YTMA79 and R(2) = 0.23-0.32, P < .001 for YTMA140). No consistent association between the level of TIL subtypes and age, sex, smoking history, tumor size, stage, and histology type was found. In univariate analysis, an elevated CD3 or CD8 signal was statistically significantly associated with longer survival in both collections. However, only CD8 was independent from age, tumor size, histology, and stage in multivariable analysis. High CD20 was associated with longer survival in the YTMA79 cohort.

Conclusions: Increased levels of CD3 and CD8 + TILs are associated with better outcome in NSCLC, but only CD8 is independent from other prognostic variables. Objective measurement of TIL subpopulations could be useful to predict response or evaluate the local immune effect of anticancer immune checkpoint inhibitors.