Abstract P2-04-24: Changes of tumor-infiltrating lymphocytes and programmed death-ligand1 positivity after neoadjuvant chemotherapy in patients with locally advanced breast cancer

Abstract

Abstract Background Recently, the balance in immune system between immune surveillance and tolerance is known to be associated with the prognosis of breast cancer patients. The aim of this study was to investigate changes of tumor-infiltrating lymphocytes (TILs) and programmed death-ligand1 (PD-L1) status after neoadjuvant chemotherapy (NAC) and their impact on recurrence in patients with locally advanced breast cancer. Methods Paired samples (before and after NAC) of triple negative or HER2+ breast cancer tissue were obtained from clinical stage II or III patients (n=39) undergoing NAC and subsequent breast resection. The assessment of immunohistochemical (IHC) staining for PD-L1 were performed. Immunostaining of forkhead box P3 (Foxp3) and CD4/CD8 were performed for subtyping of TILs in triple negative breast cancer (TNBC) only. Clinicopathologic data including baseline characteristics, tumor response and recurrence were reviewed. Results Proportion of PD-L1 (+) tumor cells in pre-chemotherapy tissue was 20% (5/25) in HER2+ and 28.6% (4/14) in TNBC. It could not predict pathologic complete response. Most post-chemotherapy tissue (21/24) showed same PD-L1 positivity with pre-chemotherapy tissue. The rest showed the decreased PD-L1 positivity after NAC. In cases of TNBC, the increased number of CD8+ T cells was significantly associated with PD-L1 positivity in pre-chemotherapy tissue. (p=0.001) Foxp3+ T cell proportions decreased significantly (p=0.046) and CD8+/Foxp3+ T-cell ratio increased significantly (p=0.023) after NAC. The patients with increased number of CD8+ T cells after NAC had a tendency to live longer without recurrence compared to patients with decreased CD8+ T cells (62.3 vs 38.1 months, p=0.158). Conclusion Our data provides the clinical evidence that PD-L1 positivity are associated with CD8+ T cell proportion and increased CD8+ T cells after NAC might be good prognostic marker. The role of immunologic balance as a prognostic marker for recurrence must be evaluated in future study. Citation Format: Choi YJ, Lee JH, Moon SY, Choi JY, Jung SP, Bae JW, Park KH. Changes of tumor-infiltrating lymphocytes and programmed death-ligand1 positivity after neoadjuvant chemotherapy in patients with locally advanced breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-24.