High platelet-to-lymphocyte ratios in triple-negative breast cancer associates with immunosuppressive status of TILs

Background Rating lymphocytes (TILs) are a prognostic marker in breast cancer and high TIL infiltration correlates with better patient outcomes. Meanwhile, parameters involving immune cells in peripheral blood have also been established as prognostic markers. High platelet-to-lymphocyte ratios (PLRs) and neutrophil-to-lymphocyte ratios (NLRs) are related to poor outcomes in breast cancer, but their mechanisms remain unknown. To date, TILs and these parameters have been examined separately. Methods We investigated the relationship between TILs and the peripheral blood markers, PLR and NLR, in the same patients, using surgical specimens from 502 patients with invasive breast carcinoma without preoperative chemotherapy. For analysis of triple-negative breast cancer (TNBC) patient outcomes, 59 patients who received preoperative chemotherapy were also examined. For immune cell profiling, multiplexed fluorescent immunohistochemistry (mfIHC) of CD3, CD4, CD8, FOXP3 and T-bet, was conducted. Results A positive correlation between PLR and TIL was observed in TNBC ( P = 0.013). On mfIHC, tumors in patients with high PLR and NLR contained more CD3 + CD4 + FOXP3 + T-cells ( P = 0.049 and 0.019, respectively), while no trend was observed in CD8 + T-cells. TNBC patients had different patterns of outcomes according to TIL and PLR, with the TIL-high/PLR-low group having the lowest rate of disease relapse and death, and the longest distant metastasis-free and overall survivals, while the TIL-low/PLR-high group had the shortest survivals. Conclusions Our data suggest that the combination of PLR with TIL assessment may enable more accurate prediction of patient outcomes with TNBC.