Assessing Tumor-Infiltrating Lymphocytes in Solid Tumors: A Practical Review for Pathologists and Proposal for a Standardized Method from the International Immuno-Oncology Biomarkers Working Group: Part 2: TILs in Melanoma, Gastrointestinal Tract Carcinomas, Non–Small Cell Lung Carcinoma and Mesothelioma, Endometrial and Ovarian Carcinomas, Squamous Cell Carcinoma of the Head and Neck, Genitourinary Carcinomas, and Primary Brain Tumors

Abstract

Assessment of the immune response to tumors is growing in importance as the prognostic implications of this response are increasingly recognized, and as immunotherapies are evaluated and implemented in different tumor types. However, many different approaches can be used to assess and describe the immune response, which limits efforts at implementation as a routine clinical biomarker. In part 1 of this review, we have proposed a standardized methodology to assess tumor infiltrating lymphocytes (TILs) in solid tumors, based on the International Immuno-Oncology Biomarkers Working Group guidelines for invasive breast carcinoma. In part 2 of this review, we discuss the available evidence for the prognostic and predictive value of TILs in common solid tumors, including carcinomas of the lung, gastrointestinal tract, genitourinary system, gynecological system, and head and neck, as well as primary brain tumors, mesothelioma and melanoma. The particularities and different emphases in TIL assessment in different tumor types are discussed. The standardized methodology we propose can be adapted to different tumor types and may be used as a standard against which other approaches can be compared. Standardization of TIL assessment will help clinicians, researchers and pathologists to conclusively evaluate the utility of this simple biomarker in the current era of immunotherapy.

Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images

“…As seen in the recommendations from of the International TILs Working Group (Salgado et al, 2015), International Immuno-oncology Biomarkers Working Group (Hendry et al, 2017a, 2017b), and the prognostic descriptions used to characterize TILs in cutaneous melanoma (Crowson et al, 2006), pathologists classify patterns within the TIL maps in both the intratumoral and peritumoral regions. Correspondingly, patterns in the 5,202 TIL maps were visually assigned by a pathologist into one of five categories: “ Brisk, diffuse ” for diffusely infiltrative TILs scattered throughout at least 30% of the area of the tumor (1,856 cases); “ Brisk, band-like ” for immune responses forming band-like boundaries bordering the tumor at its periphery (1,185); “ Non-brisk, multi-focal ” for loosely scattered TILs present in less than 30% but more than 5% of the area of the tumor (1,083); “ Non-brisk, focal ” for TILs scattered throughout less than 5% but greater than 1% of the area of the tumor (874); and finally “ None ” in 143 cases where few TILs were present involving 1% or less of the area of the tumor (see Method Details).…”

The adequacy of tissue microarrays in the assessment of inter- and intra-tumoural heterogeneity of infiltrating lymphocyte burden in leiomyosarcoma

“…The cohort medians of average TIL/HPF were CD3: 16.5 (IQR 11.3-30.9), CD4: 10.5 (IQR 5.5-18.9), CD8: 16.1 (IQR 7.2-23.0). These median values are below the 'low infiltration' thresholds currently used in studies of TILs in other well-studied cancer types such as melanoma, nonsmall cell lung cancer (NSCLC) and colorectal cancer [33][34][35][36][37] .…”

“…To address the question of how many TMA cores must be sampled from a tumour to provide adequate representation of the overall TIL burden of a tumour, we devised an in silico 'virtual TMA' (vTMA) that would allow for the iterative sampling of a number of cores that would be impractical for a physical TMA. We then assessed how many cores were required to produce an estimate of TIL burden that either (i) accurately recapitulated the true TIL burden of a tumour, or (ii) was sufficiently accurate to identify whether a tumour had high or low TIL burden, relative to the median or quartile TIL values of the entire cohort-this second approach was based on the observation that, in many published studies that have demonstrated clinical relevance of TIL numbers, similar rank-based categorisation was used, often based on dichotomisation around cohort median value 37 .…”

“…However, many studies that have described an association between TILs and clinical outcome ultimately applied cut-off thresholds to assign TIL counts into ordinal categories (e.g. 'high' or 'low' infiltration) that reflect relative rather than absolute degree of infiltration 37 . We found that sampling only 1 core was sufficient to correctly identify a majority of tumours as has having a 'high' or 'low' degree of infiltration, while 2-5 cores was adequate to correctly identify a majority of tumours as having 'very low', 'low', 'high' or 'very high' degree of TIL infiltration, based on categorical cut-offs at cohort quartiles.…”

Bioengineering a novel 3D in-vitro model to recreate physiological oxygen levels and tumor-immune interactions

“…Patients with tumors that are poorly oxygenated have an increased risk of mortality (22). In addition, the presence of tumor-infiltrated lymphocytes (TILs) can be used as a relevant prognostic indicator (23)(24)(25). A notorious hallmark associated with BCa intratumoral oxygen deprivation is alteration in the cancer cell survival metabolism to function through the hypoxia-inducible factor-1α (HIF-1α) regulatory pathway (26)(27)(28).…”