The importance of stromal and intratumoral tumor lymphocyte infiltration for pathologic complete response in patients with locally advanced breast cancer.

Objective: Increased tumor-infiltrating lymphocytes (TILs) in breast carcinoma tissues is an independent predictive factor for pathologic complete response (pCR). The increased intratumoral and stromal TILs (sTILs) in breast cancer (BC) have significant prognostic effects. In this study, we evaluated whether pCR rates to neoadjuvant chemotherapy (NACT) are higher in tumors with increased number of TILs in the pretreatment biopsy.

Materials And Methods: We retrospectively evaluated the number of TILs in intratumoral TILs (iTILs) and sTILs compartments from pretreatment full-face hematoxylin and eosin-stained sections of 62 patients with locally advanced BC (LABC) who received NACT. The capacity of sTILs and iTILs in predicting pCR to NACT in LABC analyzed using receiver operating characteristic (ROC) curve analysis.

Results: According to ROC curve analysis, the optimum sTILs and iTILs cut-off points (the number of positive cells per square millimeter of tissue) for patients with LABC patients with pCR (+) were 19 (area under the curve (AUC): 0.668, 95% confidence interval [CI] [0.501-0.835],P = 0.064) and 4 (AUC: 0.786, 95%CI [0.666-0.907],P = 0.002), respectively. Of the 62 patients, 26 had sTILs >19 and 25 had iTILs >4. The patients were divided into two according to percent of sTILs (sTILs >19 and sTILs ≤19 groups) and iTILs (iTILs >4 and iTILs ≤4 groups). Both sTILs >19 and iTILs >4 patients were associated with development higher pCR. While pCR was significantly higher in iTILs >4 patients (P = 0.002), it was not significantly in sTILs >19 patients (P = 0.107).

Conclusions: There is significantly an association between pCR and increased number of intratumoral TILs (>4 cells/mm of tissue) in BC who received NACT.