Abstract ES6-3: Tumor infiltrating lymphocytes in breast cancer

Abstract

Abstract Interest in evaluating the presence of tumor infiltrating lymphocytes (TILs) in breast cancer is growing due to robust data supporting significant prognostic associations as well as the success of the new T cell checkpoint inhibitors in other solid organ cancer types. The positive prognostic associations between TILs present at diagnosis in triple negative (TN) and HER2-overexpressing breast cancer and better outcomes after standard adjuvant therapy strongly suggests that these breast cancer subtypes will be amendable to immunotherapeutic approaches. Current research suggests that TILs represent pre-existing host anti-tumor immunity, with the data reporting that the more TILs that are present in the tumor at diagnosis, the stronger the pre-existing immune response and better clinical outomes. However, only a minority of patients present with high levels of TILs at diagnosis. Current data also reports that biopsies from metastatic disease still can contain significant amounts of TILs. This suggests that these patients can generate an immune response even in advanced disease, albeit weak, as the median values of TILs present seem to be less. This presentation will discuss the data on the prognostic associations of TILs, our current understanding about the content of TILs in breast cancer and how they could be potentially triggered and/or suppressed. I will also discuss our recently published guidelines on how to evaluate TILs in breast cancer (Salgado R et al, 2014). Furthermore I will speculate on how we could potentially augment or re-kick start a more effective anti-tumor immune response in patients with breast cancer. I will also talk about the potential future clinical utility of TILs in breast cancer- it is currently not recommended that TILs are used in treatment decision-making concerning chemotherapy or no chemotherapy in TN breast cancer or trastuzuamb vs no trastuzumab in HER2-positive disease. Phase II efficacy data evaluating T cell checkpoint inhibitors is not yet available in advanced TN and HER2-positive breast cancer, however, phase I data using monotherapy T cell checkpoint inhibition in heavily pre-treated disease seems promising with objective responses meeting RECIST criteria seen. It is unclear what the best biomarker will be in breast cancer patients for immunotherapeutic approaches, but targeting patients with some degree of already pre-existing anti-tumor immunity seems logical. Citation Format: Sherene Loi. Tumor infiltrating lymphocytes in breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr ES6-3.