Changes in the tumor immune microenvironment in resected recurrent soft tissue sarcomas.

Little is known about how the tumor immune microenvironment (TIME) is modulated in recurrent soft tissue sarcomas (STS). We evaluated CD8+ T cells, CD20+ B cells, Foxp3+ regulatory T cells (Tregs), and programmed cell death ligand 1 (PD-L1) in 72 paired pre-recurrent (1st resected) versus post-recurrent (2nd resected) STS by immunohistochemistry. Correlations with time to recurrence and prognosis were determined. We found that CD8, PD-L1, CD20, and Foxp3-positive cell counts changed in post-recurrent STS. PD-L1-positive tumor cell and lymphocyte counts increased in post-recurrent STS, whereas CD8+ T cell counts decreased. Changes in CD8+ T cell, CD20+ B cell, and PD-L1+ lymphocyte counts were associated with the time interval between surgeries. At admission, fewer CD8+ T cells were detected in patients with relapse than in newly diagnosed patients. Furthermore, post-recurrent STS with fewer CD8+ T cells compared with pre-recurrent STS were more likely to exhibit re-recurrence. The change in CD8+ T cells was positively associated with overall survival. In multivariate analyses, a decrease in CD8+ T cell counts in post-recurrent STS was an independent unfavorable prognostic factor. The TIME differs between pre-recurrent STS and post-recurrent STS. The variation in CD8+ T cells and PD-L1 positivity may have essential roles during tumor relapse and provides a basis for determining therapeutic strategies.