Abstract ES4-3: Tumor-infiltrating lymphocytes (TILs) and genomic signatures of immune cells
Authors: Denkert C 
Published: March 2017

Abstract
Increased levels of tumor-infiltrating lymphocytes have been described in subsets of breast cancer, in particular triple-negative (TNBC) and HER2-positive (HER2+) tumors. Neoadjuvant therapy approaches in breast cancer have been used as a strategy to characterize subgroups of tumors with increased tumor-infiltrating lymphocytes (TILs). We have described tumor-infiltrating lymphocytes (TILs) as predictors of pathological complete response to neoadjuvant chemotherapy in breast cancer trials conducted by the German Breast Group. It has been shown that increased TILs are linked to an increased response rate to neoadjuvant therapy and improved prognosis after adjuvant therapy, in particular in triple-negative and HER2 positive breast cancer. In addition to tumor-infiltrating lymphocytes, immune mRNA markers have been studied in breast cancer and are associated with increased chemotherapy response and improved prognosis. These results suggest that some subtypes of breast cancer are immunogenic and that there is an ongoing low-level immune response present even in clinically progressing tumors.
Therapeutic approaches to modulate tumor-associated inflammation by immune checkpoint inhibitors have shown clinical responses in a subset of triple-negative breast cancers, and some of these responses were durable. These targeted therapies have stimulated interest in the interaction between immune cells and tumor cells. Based on the concept that conventional chemotherapy might be immunogenic, some studies are evaluating the combination of an immune checkpoint inhibitor and a chemotherapy. Considering the fact that responses to immune checkpoint inhibitors are observed in only a subset of tumors, biomarkers that will be able to identify those tumors are needed. Possible biomarkers include the therapeutic targets, in particular PD-L1 and PD1, tumor-infiltrating lymphocytes, predictive mRNA signatures, immunogenic neoepitope signatures that are generated by mutations as well as other factors. Due to the low costs of a simple H&E based test, tumor infiltrating lymphocytes might become a promising biomarker as part of the pathology report. In preparation for this, the international immune-oncology working group (TIL working group) has published standardized guidelines for TIL evaluation in breast cancer, and has conducted a first international TIL ring trial. This ring trial suggests that decentral TIL evaluation is feasible. In some situations, in particular in tumors with intermediate and heterogeneous TILs, additional tests, including gene expression signatures might be necessary. It should be emphasized that the clinical utility of TILs for current medical decisions is very limited at the present time, and the ultimate usefulness of these biomarker concepts will be obtained in the ongoing and future clinical immunotherapy trials.
The presentation will provide an overview on recent results on immune markers for prediction of response to neoadjuvant chemotherapy and prognosis with a focus in standardized histomorphological evaluation of tumor-infiltrating lymphocytes as well as clinical trials concepts and biomarker strategies for future immune checkpoint inhibitor therapies in breast cancer.
Citation Format: Denkert C. Tumor-infiltrating lymphocytes (TILs) and genomic signatures of immune cells [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 ES4-3.