TILGen: A Program to Investigate Immune Targets in Breast Cancer Patients - First Results on the Influence of Tumor-Infiltrating Lymphocytes

Abstract

Background: Despite advancements in the treatment of primary and metastatic breast cancer, many patients lack a durable response to these treatments. Patients with triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2(HER2)-positive breast cancer who do not have a pathological complete response (pCR) after neoadjuvant chemotherapy (NACT) have a very poor prognosis. Tumor-infiltrating lymphocytes (TILs) have been identified as a predictive marker for pCR after NACT in TNBC and HER2-positive breast cancer. These patient populations could also be suitable for novel treatment strategies including neoepitope-based therapies. This work analyses the effect of TILs on the pCR in neoadjuvantly treated patients in the TILGen study and presents the procedures aimed at establishing neoepitope-based therapies in this study.

Methods: Neoadjuvantly treated HER2-positive and TNBC patients were eligible for the presented analysis concerning the association between TILs and pCR. A total of 146 patients could be identified within the TILGen study. TILs were evaluated as percentage of stromal tumor tissue in core biopsies at primary diagnosis. The phenotype 'lymphocyte-predominant breast cancer' (LPBC) was associated with pCR by logistic regression adjusted for estrogen receptor status, progesterone receptor status, HER2 status, age at diagnosis, and grading.

Results: LPBC was seen in 24 (16.4%) patients. In this patient group, 66.7% achieved a pCR, while the pCR rate was 32.8% in patients with a low TIL count. The adjusted odds ratio was 6.60 (95% confidence interval 2.02-21.56; p < 0.01).

Conclusion: TILs are a strong predictor of pCR in TNBC and HER2-positive breast cancer patients. Implications for the use of this information including the effect on prognosis might help to identify patients most likely to benefit from a neoepitope-based therapy approach.

Keywords: Neoadjuvant chemotherapy; Response; TILGen study; Tumor-infiltrating lymphocytes.

Fig. 1

Procedures at study inclusion and selection of TILGen participants.

Fig. 2

Patient selection table of the iMODE-B study for tumor-infiltrating lymphocyte (TIL) analysis.

Fig. 3

Pathological complete response (pCR) rates in non-lymphocyte-predominant breast cancer (non-LPBC) versus LPBC. pCR after neoadjuvant chemotherapy was defined according to Sinn et al. [37].

Fig. 4

Objective and strategy of the TILGen study and therapy concept. The overall objective of the TILGen study is the identification of tumor-specific antigens (TSAs)/neoepitopes as well as TSA-specific T cells, and the implementation of TSA/neoepitope-specific targeted therapy. The workflow with each working step is illustrated in numbers (1–16): 1) blood sample collection for isolation of germline DNA; 2) collection of fresh frozen breast cancer core biopsies for isolation of tumor DNA and RNA; 3) isolation and cultivation of antigen-presenting cells (APCs); 4) T-cell expansion out of tumor-infiltrating lymphocytes (TILs) from core biopsy; 5) whole genome sequencing; 6) determination of likely antigenic sequences by comparing germline and tumor DNA; 7) synthesis of likely antigenic peptides; 8) loading of antigenic peptides on APCs; 9) co-cultivation of peptide-loaded APCs and isolated tumor T cells to measure T cell response and identify TSAs and TSA-specific T cell clones; 10) production of cancer vaccine with regard to TSA; 11) expansion of TSA-specific T cells; 12) production of chimeric antigen receptor (CAR) natural killer cells (NK) or CAR T cells; 13) production of TSA-specific humanized antibodies; 14) low-dose radiation therapy; 15) metronomic chemotherapy; 16) treatment option with e.g. metronomic chemotherapy in combination with TSA vaccination, TSA-specific T cells, and radiation.