High Interobserver Variability Among Pathologists Using Combined Positive Score to Evaluate PD-L1 Expression in Gastric, Gastroesophageal Junction, and Esophageal Adenocarcinoma.

Reliable, reproducible methods to interpret programmed death ligand-1 (PD-L1) expression on tumor cells (TC) and immune cells (IC) are needed for pathologists to inform decisions associated with checkpoint inhibitor therapies. Our international study compared interpathologist agreement of PD-L1 expression using the combined positive score (CPS) under standardized conditions on samples from patients with gastric/gastroesophageal junction/esophageal adenocarcinoma. Tissue sections from 100 adenocarcinoma pretreatment biopsies were stained in a single laboratory using the PD-L1 immunohistochemistry 28-8 and 22C3 (Agilent) pharmDx immunohistochemical assays. PD-L1 CPS was evaluated by 12 pathologists on scanned whole slide images of these biopsies before and after a 2-hour CPS training session by Agilent. Additionally, pathologists determined PD-L1-positive TC, IC, and total viable TC on a single tissue fragment from 35 of 100 biopsy samples. Scoring agreement among pathologists was assessed using the intraclass correlation coefficient (ICC). Interobserver variability for CPS for 100 biopsies was high, with only fair agreement among pathologists both pre- (range, 0.45-0.55) and posttraining (range, 0.56-0.57) for both assays. For the 35 single biopsy samples, poor/fair agreement was also observed for the total number of viable TC (ICC, 0.09), number of PD-L1-positive IC (ICC, 0.19), number of PD-L1-positive TC (ICC, 0.54), and calculated CPS (ICC, 0.14), whereas calculated TC score (positive TC/total TC) showed excellent agreement (ICC, 0.82). Retrospective histologic review of samples with the poorest interpathologist agreement revealed the following as possible confounding factors: (1) ambiguous identification of positively staining stromal cells, (2) faint or variable intensity of staining, (3) difficulty in distinguishing membranous from cytoplasmic tumor staining, and (4) cautery and crush artifacts. These results emphasize the need for objective techniques to standardize the interpretation of PD-L1 expression when using the CPS methodology on gastric/gastroesophageal junction cancer biopsies to accurately identify patients most likely to benefit from immune checkpoint inhibitor therapy.

Clinicopathological and prognostic significance of PD-L1 expression in colon adenocarcinoma tumor budding.

OBJECTIVE: In this study, we investigated the relationship between programmed cell death ligand 1 (PD-L1) and programmed cell death protein 1 (PD-1) expression in colon adenocarcinoma tumor budding. METHODS: This study included 122 patients with colon adenocarcinomas. The largest sample of formaldehyde-fixed paraffin-embedded tumor tissues was selected for analysis. Expression of membranous PD-L1 (clone 22C3) and the Combined Positive Score (CPS) in tumor tissues was calculated and graded according to the percentages of peritumoral and intratumoral tumor cells (0 %, 1 %, 1-5 %, >5 %). The effects of these factors on the prognosis were analyzed. RESULTS: Tumor budding was associated with adverse clinicopathological features and poor overall survival. PD-L1 (CPS%) peritumoral tumor budding (1 %/<1 %) was statistically significant in the univariate model (p = 0.004). Age, organ metastases (liver, lung, liver, lung, and peritoneum), and metastases were statistically significant in the multivariate model (p = 0.001, p = 0.004, p = 0.001, p = 0.002, p = 0.004, and p = 0.032, respectively). PD-L1 positive staining was mostly observed around the tumor and during tumor budding. PD-L1 peritumoral tumor budding rates and patients' survival rates differed significantly (log-rank = 12.07, p = 0.007). CONCLUSION: We found that patients with PD-L1 (CPS%) > 1 % in tumor budding had a shortened life expectancy and demonstrated the importance of including tumor budding areas in the samples used for biomarker evaluation. We previously reported that PD-L1 expression in tumor budding is associated with more aggressive cancer biology and poor survival, although overall survival is of limited statistical significance.

The predictive and prognostic value of Foxp3+/CD25+ regulatory T cells and PD-L1 expression in triple negative breast cancer.

Recent significant developments in cancer immunotherapy have led to important breakthroughs and paradigm shifts in the treatment of malignancy. Although breast cancer traditionally has been considered less immunogenic, triple-negative breast cancer (TNBC) is the most immunogenic subtype with more stromal tumor-infiltrating lymphocytes (TILs) and higher programmed death-ligand 1 (PD-L1) expression. The goal of this study is to evaluate regulatory T cells (Tregs) and PD-L1 expression in TNBC, as well as their associations with clinicopathologic features and the outcomes. Tissue microarrays (TMA) of biopsy and resection specimens of 43 TNBC patients who underwent breast biopsy, neoadjuvant chemotherapy, and mastectomy were prepared. The number of Foxp3+ Tregs, Foxp3+/CD25+ Tregs, and expression of PD-L1 in tumor cells (PD-L1 TCs) and TILs (PD-L1 TILs) were assessed by immunohistochemistry. PD-L1 expression combined positive score (PD-L1 CPS) was calculated according to the manufacturer's guidelines. PD-L1 expression was detected in 72% of the cases, and it expressed in a higher percentage and higher intensity in TILs than TCs in TNBC (p = 0.006 and 0.0005, respectively). PD-L1 TCs, PD-L1 TILs, and PD-L1 CPS were all positively associated with pathologic complete response (pCR) (p = 0.04, 0.03, and 0.02, respectively). PD-L1 TILs and PD-L1 CPS also correlated with TILs and tumor infiltrating lymphocyte volume (TILV). Foxp3+ Tregs and Foxp3+/CD25+ Tregs had strong positive correlation (r = 0.89), and they were positively associated with TILs, TILV, and PD-L1 expression. Foxp3+/CD25+ Tregs, PD-L1 TCs, and PD-L1 CPS were positively correlated with better overall survival (p = 0.04, 0.04 and 0.01, respectively).

Interpretation of PD-L1 expression in gastric cancer: summary of a consensus meeting of Korean gastrointestinal pathologists.

Nivolumab plus chemotherapy in the first-line setting has demonstrated clinical efficacy in patients with human epidermal growth factor receptor 2-negative advanced or metastatic gastric cancer, and is currently indicated as a standard treatment. Programmed death-ligand 1 (PD-L1) expression is an important biomarker for predicting response to anti-programmed death 1/PD-L1 agents in several solid tumors, including gastric cancer. In the CheckMate-649 trial, significant clinical improvements were observed in patients with PD-L1 combined positive score (CPS) ≥ 5, determined using the 28-8 pharmDx assay. Accordingly, an accurate interpretation of PD-L1 CPS, especially at a cutoff of 5, is important. The CPS method evaluates both immune and tumor cells and provides a comprehensive assessment of PD-L1 expression in the tumor microenvironment of gastric cancer. However, CPS evaluation has several limitations, one of which is poor interobserver concordance among pathologists. Despite these limitations, clinical indications relying on PD-L1 CPS are increasing. In response, Korean gastrointestinal pathologists held a consensus meeting for the interpretation of PD-L1 CPS in gastric cancer. Eleven pathologists reviewed 20 PD-L1 slides with a CPS cutoff close to 5, stained with the 28-8 pharmDx assay, and determined the consensus scores. The issues observed in discrepant cases were discussed. In this review, we present cases of gastric cancer with consensus PD-L1 CPS. In addition, we briefly touch upon current practices and clinical issues associated with assays used for the assessment of PD-L1 expression in gastric cancer.

PD-L1 Expression in Paired Samples of Rectal Cancer.

Immune checkpoint inhibitors and immune-related biomarkers are increasingly investigated in rectal cancer (RC). We retrospectively analysed PD-L1 expression in diagnostic biopsy and resection samples from RC patients treated at our centre between 2000 and 2020. PD-L1 immunostaining (22C3 clone) was evaluated according to tumour proportion (TPS), immune cell (ICS), and the combined positive score (CPS). Eighty-three patients were included. At diagnosis, PD-L1 expression ≥1%/≥5% was observed in 15.4%/0%, 80.7%/37.4%, and 69.2%/25.6% of patients based on TPS, ICS, and CPS, respectively. At surgery, the respective figures were 4.6%/1.5%, 60.2%/32.5%, and 50.7%/26.2%. Using the 1% cut-off and regardless of the scoring system, PD-L1 was less expressed in surgery than biopsy samples (p ≤ 0.04). In paired specimens, PD-L1-ICS reduction was especially observed following neoadjuvant long-course (chemo)radiotherapy (p = 0.03). PD-L1-ICS of ≥5% in surgical samples (HR: 0.17; p = 0.02), and a biopsy-to-surgery increase in PD-L1-ICS (HR: 0.19; p = 0.04) was predictive for longer disease-free survival, while the PD-L1-ICS of either ≥1% (HR 0.28; p = 0.04) or ≥5% (HR 0.19; p = 0.03) in surgical samples and the biopsy-to-surgery increase in PD-L1-ICS (HR: 0.20; p = 0.04) were associated with better overall survival. Our study suggests that PD-L1 expression in RC is largely reflective of immune cell infiltration, and its presence/increase in surgical samples predicts better outcomes.

Acute myeloid leukemias with JAK2/STAT mutations are associated with PD-L1 upregulation.

Even though overexpression of the immune checkpoint protein, programmed cell death ligand-1 (PD-L1), is observed in solid tumors, its expression patterns in acute myeloid leukemia remain understudied. As activation of the JAK/STAT pathway has been shown to enhance PD-L1 expression in preclinical models, we evaluated biopsies from AML patients with activating mutations in JAK2/STATs. PD-L1 expression was significantly upregulated in JAK2/STAT mutant cases when compared to JAK2 wildtype controls as demonstrated by PD-L1 immunohistochemistry staining and quantified using the combined positive score (CPS) system. There is significant overexpression of phosphorylated STAT3 expression in patients with oncogenic JAK2 activation and a positive correlation between p-STAT3 and PD-L1 expression. In conclusion, we demonstrate the CPS scoring system could be applied as a quantitative measure of PD-L1 expression in leukemias and that JAK2/STATs mutant AML can be potential candidates for checkpoint inhibitor trials.

The clinicopathological significance of PD-L1 expression assessed by the combined positive score (CPS) in head and neck squamous cell carcinoma.

The expression of programmed cell death-ligand 1 (PD-L1) is being used as a predictive biomarker for immunotherapy in head and neck squamous cell carcinoma (HNSCC). Our study was a retrospective cohort that assessed PD-L1 expression levels through immunohistochemistry (IHC) in 119 surgical specimens from HNSCC patients. The expression of PD-L1 was evaluated by IHC staining using the monoclonal antibody 22C3 (Dako) and the combined positive score (CPS). The relationship between the PD-L1 expression and clinicopathologic features was analyzed. 107 cases (89.9%) and 52 cases (43.7%) were positive for PD-L1 expression when the CPS cutoff value was set at 1 and 20 respectively. The tumor stage (P = 0.022) and tumor site (P = 0.004) were significantly correlated with the PD-L1 expression (CPS ≥ 1). Non-diabetic patients (P = 0.046) were corelated to positive PD-L1 expression (CPS ≥ 20). When evaluating PD-L1 expression in 40 laryngeal squamous cell carcinomas (LSC), the nodal stage was found to be significantly associated with high expression of PD-L1 (CPS ≥ 20) (P = 0.042). As for 36 patients with hypopharyngeal squamous cell carcinomas (HPSC), the positive PD-L1 expression (CPS ≥ 1) were typically younger (P = 0.030) and patients without type II diabetes (P = 0.040). We evaluated all possible clinical prognostic factors in the univariate Cox model, and there was no significant correlation between clinical characteristics and survival. The results of our findings may help to understand the association between the PD-L1 expression and clinicopathological characteristics, and it showed no significant correlation between the expression of PD-L1 and OS in HNSCC.

Role of Immune Checkpoint Inhibitors in Gastrointestinal Malignancies.

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of several solid and hematological malignancies. ICIs are not only able to produce long and durable responses, but also very well tolerated by patients. There are several approved indications of use of ICIs in treatment of metastatic gastrointestinal malignancies including gastric, esophageal, colorectal and hepatocellular carcinoma. In addition, ICIs can be used in microsatellite instability-high (MSI-H) and high tumor mutational burden (TMB) tumors in chemotherapy-resistant setting. Despite having good efficacy and superior safety profile, ICIs are clinically active in small subset of patients, therefore, there is a huge unmet need to enhance their efficacy and discover new predictive biomarkers. There are several ongoing clinical trials that are exploring the role of ICIs in various gastrointestinal cancers either as single agent or in combination with chemotherapy, radiation therapy, targeted agents or other immunotherapeutic agents. In this review, we discuss the published and ongoing trials for ICIs in gastrointestinal malignancies, including esophageal, gastric cancer, pancreatic, hepatocellular, biliary tract, colorectal and anal cancers. Specifically, we focus on the use of ICIs in each line of therapy and discuss the future directions of these agents in each type of gastrointestinal cancer.

Pembrolizumab for the treatment of esophageal cancer.

INTRODUCTION: Esophageal cancer (EC) is the seventh most common cancer and the sixth leading cause of cancer death. However, the prognosis of unresectable advanced or recurrent EC patients remains poor and there are few effective therapeutic agents for EC. Pembrolizumab is a monoclonal antibody that exerts anti-tumor activity by inhibiting the interaction of programmed cell death protein 1 with its ligand (PD-L1) on activated lymphocytes. Pembrolizumab monotherapy shows a significant survival benefit in metastatic or recurrent EC patients with PD-L1 CPS ≥10 as second-line treatment. AREA COVERED: In this review, we provide an overview of pembrolizumab as a compound and present the available clinical data related to EC treatment. EXPERT OPINION: In our opinion, pembrolizumab is one of the standard treatment agents for second-line metastatic or recurrent esophageal squamous cell carcinoma patients with PD-L1 CPS ≥10. Trials assessing the efficacy of a combination of cytotoxic agents and pembrolizumab as first-line treatment and pembrolizumab-containing chemoradiation are ongoing. Their results may provide important data to improve clinical outcomes.