Targeting immune pathways in breast cancer: review of the prognostic utility of TILs in early stage triple negative breast cancer (TNBC).

Breast cancer has been one of the last tumor types to see benefit from immunotherapies. Yet, immune infiltrates have been noticed for decades in primary breast cancers. Lately, quantity of tumor infiltrating lymphocytes (TILs) have been reported to have strong prognostic value in improving estimates of distant recurrence-free survival, disease-free and overall survival in early-stage triple negative BC (TNBC) treated with standard adjuvant/neoadjuvant chemotherapy (Level 1B evidence). Quantity, as a percentage of tumor stromal infiltration, is based on an evaluation by pathologists using light microscopy on H&E stained glass slides (see method at www.tilsinbreastcancer.org) [1,2] at time of diagnosis (pre-treatment and in the residual disease post neoadjuvant chemotherapy). Whilst TILs are currently not used for treatment allocation, this is an active area of investigation. Combination of atezolizumab with nab-paclitaxel in a phase III study has recently seen success in terms of improved progression free and overall survival for the PD-L1 -positive population of metastatic TNBC in the first line/newly relapsed setting [3]. This has led to approval of atezolizumab for use in this setting. However, this population was only 41% of the trial population. Data in advanced breast cancer currently suggest requirement for enrichment of the population for preexisting anti-tumor immunity for benefit to PD(L)1 inhibition. Checkpoint inhibitors are currently being investigated in the early-stage setting in a number of phase II/III trials in TNBC with various different anti- PD-1, PD-L1 and CTLA-4 agents. In this context, we will face issues of the best chemotherapy backbone, the possible detrimental role of steroids and growth factor support, risk of overtreatment, differences between PD-1 and PD-L1 inhibition and if we can use a biomarker to effectively escalate or de-escalate chemotherapy and/or use checkpoint inhibition in this setting.

Blackley EF ，Loi S 《-》

Integration of tumour infiltrating lymphocytes, programmed cell-death ligand-1, CD8 and FOXP3 in prognostic models for triple-negative breast cancer: Analysis of 244 stage I-III patients treated with standard therapy.

Tumour infiltrating lymphocytes (TILs) are an established prognostic biomarker for triple-negative breast cancer (TNBC). We evaluated the role of programmed cell-death ligand-1 (PD-L1), CD8 and FOXP3 expression in refining a prognostic model for non-metastatic TNBC beyond classic factors and TILs. Primary tumour samples from 244 early patients with TNBC, all treated with surgery and chemotherapy, were collected. Stromal TILs were evaluated on haematoxylin-eosin slides according to guidelines. PD-L1, CD8 and FOXP3 were assessed by immunohistochemistry and evaluated by digital pathology. TILs, PD-L1, CD8 and FOXP3 were positively correlated with each other (P < 0.001). TILs were confirmed as an independent prognostic factor. When PD-L1, CD8 and FOXP3 were added to multivariable models including classic factors (age, stage, histologic grade) and TILs, PD-L1 provided the largest amount of additional prognostic information: likelihood ratio χ2 4.60, P = 0.032 (in a model including classic factors and TILs 10% increments) and likelihood ratio χ2 6.50, P = 0.011 (in a model including classic factors and TILs >30% versus <30%). In the subset of patients treated with neoadjuvant chemotherapy, FOXP3 provided further prognostic information beyond classic factors, TILs and pathological complete response (pCR) (likelihood ratio χ2 5.01, P = 0.025). For patients who did not achieve a pCR, the expression of CD8 and PD-L1 was significantly increased from baseline to residual disease. Beyond clinicopathological factors and TILs, other immune biomarkers may add prognostic information for early TNBC. The increased PD-L1 expression on residual disease after neoadjuvant chemotherapy strengthens the rationale of testing immune checkpoint inhibitors in the post-neoadjuvant setting.

Dieci MV ，Tsvetkova V ，Griguolo G ，Miglietta F ，Tasca G ，Giorgi CA ，Cumerlato E ，Massa D ，Lo Mele M ，Orvieto E ，Guarneri V ，Conte P ... -  《-》

The combination of PD-L1 expression and decreased tumor-infiltrating lymphocytes is associated with a poor prognosis in triple-negative breast cancer.

Mori H ，Kubo M ，Yamaguchi R ，Nishimura R ，Osako T ，Arima N ，Okumura Y ，Okido M ，Yamada M ，Kai M ，Kishimoto J ，Oda Y ，Nakamura M ... -  《Oncotarget》

The therapeutic candidate for immune checkpoint inhibitors elucidated by the status of tumor-infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) expression in triple negative breast cancer (TNBC).

Tomioka N ，Azuma M ，Ikarashi M ，Yamamoto M ，Sato M ，Watanabe KI ，Yamashiro K ，Takahashi M ... -  《-》

The journey of tumor-infiltrating lymphocytes as a biomarker in breast cancer: clinical utility in an era of checkpoint inhibition.

In 2014, we described a method to quantify percentage of tumor-infiltrating lymphocytes (TILs) on hematoxylin and eosin-stained slides of breast cancer samples using light microscopy that could be performed easily by pathologists with no extra stains. The aim of detailing the method was to facilitate independent research groups replicating our prognostic findings using TIL quantity in early-stage breast cancers. A global working group of breast pathologists was convened to standardize, test reproducibility, and refine the method. A website was also established which allowed free training (www.tilsinbreastcancer.org). As a result of this work, TIL data have been collected in over 20 000 primary breast cancer samples worldwide and the robust associations with better prognoses in triple-negative breast cancer (TNBC) and HER2+ BC have been confirmed. This has resulted in the inclusion of the TIL biomarker in several international breast cancer guidelines as well as in national criteria for routine pathology reporting. TIL therefore represents the first biological prognostic biomarker for early-stage TNBCs, and here its prognostic effect is linear, with values of 30%-50% being suggested as suitable for use in potential chemotherapy de-escalation studies. The efficacy of immune checkpoint-targeted agents in breast cancer now provides direct evidence that host immune responses can modify tumor growth in some patients. With the recent granting of accelerated approvals for the first PD-1/PD-L1 targeting agents in early and advanced TNBC, our focus has now moved to investigating the clinical utility of TIL in the setting of immune checkpoint agents, with or without PD-L1 protein assessment. Emerging data suggest that TIL quantity can help clinicians identify patients with breast cancer who benefit most from PD-1/PD-L1 inhibition. In patients with advanced TNBC and HER2+ disease a TIL cut-off of 5% or 10%, with PD-L1 expression can define 'immune-enriched' tumors and currently seems to have the most clinical relevance in this context.

Loi S ，Michiels S ，Adams S ，Loibl S ，Budczies J ，Denkert C ，Salgado R ... -  《-》