Tumor infiltrating lymphocytes (TILs) and the expression of programmed death ligand 1 (PD-L1) as predictors for the response rate of preoperative systemic therapy (PST) and prognosis in triple-negative breast cancer (TNBC).

157 Background: The status of tumor infiltrating lymphocytes (TILs) is known to be prognostic for triple negative breast cancer (TNBC) due to its correlation with chemosensitivity. Moreover, to regulate the pathway of immune-checkpoint molecules is also expected to improve the prognosis of TNBC. The relevancy of these two factors could be attractive concerning on the immune interaction which might play an important role in the prognosis of TNBC. Methods: Patients with TNBC are 277 among 2371 who were underwent surgery between January 2002 and December 2011. Out of 90 patients received preoperative systemic therapy (PST), 32 patients’ specimens of core needle biopsy were available for review for TILs. The TILs was scored as “% stromal” by pathologist who feels comfortable with through the scan for single whole section according to the recommendations by an International TILs Working Group 2014. The expression of programmed death ligand 1 (PD-L1) was assessed by immunohistochemistry, which was defined 3 stages as negative or positive (weak or strong) by the pathologist in our facility. The statistical analysis for variance was done by Mann-Whitney U-test or Kruskal-Wallis test, and for survival by Kaplan Meier method was evaluated by Logrank test. Results: TILs’ score was defined as follows (%; numbers of patients): (5; 2), (10; 8), (20; 9), (30; 7), (40; 1), (50; 1), (60; 1), (70; 2), (80; 0), (90; 1). Statistical validations for variance of TILs’ score were significant on the regression rate of tumor size: (T-pT)/T; < 2/3 v.s. 2/3 < (p= 0.0097), and pathological therapeutic grade: 1 vs 2 or 3 (p= 0.0285). When we set the threshold at 30% of TILs’ score, DFS with TILs’ score < 30% was worse significantly (p= 0.0383) but not on OS (p= 0.0772). Unfavorable group on DFS (TILs’ score < 30%) was divided again into two groups by the status of PD-L1 significantly (negative or weak v.s. strong; p= 0.0319). Conclusions: The status of TILs and PD-L1 could elucidate the candidate for the therapeutic approaches to immune-checkpoint molecules, which could make improvement of the prognosis of TNBC.