Tumour islet Foxp3⁺ T-cell infiltration predicts poor outcome in nonsmall cell lung cancer

The impact of host immunity on outcome in nonsmall cell lung cancer (NSCLC) is controversial. We examined the relationship between lymphoid infiltration patterns in NSCLC and prognosis. Tumour- and stroma-infiltrating CD3 + , CD8 + and forkhead box P3 (Foxp3) + T-lymphocytes were identified using immunohistochemistry and a novel image analysis algorithm to assess total, cytotoxic and regulatory T-lymphocyte counts, respectively, in 196 NSCLC cases. The median cell count was selected as a cut-point to define patient subgroups and the ratio of the corresponding tumour islet:stroma (TI/S) counts was determined. There was a positive association between overall survival and increased CD8 + TI/S ratio (hazard ratio (HR) for death 0.44, p<0.001) but an inverse relationship between Foxp3 + TI/S ratio and overall survival (HR 4.86, p<0.001). Patients with high CD8 + islet (HR 0.48, p<0.001) and Foxp3 + stromal (HR 0.23, p<0.001) counts had better survival, whereas high CD3 + and CD8 + stromal counts and high Foxp3 + islet infiltration conferred a worse survival (HR 1.55, 2.19 and 3.14, respectively). By multivariate analysis, a high CD8 + TI/S ratio conferred an improved survival (HR 0.48, p=0.002) but a high Foxp3 + TI/S ratio was associated with worse survival (HR 3.91, p<0.001). Microlocalisation of infiltrating T-lymphocytes is a powerful predictor of outcome in resected NSCLC.