PD-L1 Testing in Cytological Non-Small Cell Lung Cancer Specimens: A Comparison with Biopsies and Review of the Literature

The impact of different fixatives on immunostaining of lung adenocarcinomas in pleural effusion cell blocks

BACKGROUND

Cell blocks (CBs) are widely used for biomarker analyses such as immunostaining. Although immunohistochemistry on formalin-fixed paraffin-embedded tissues is standardized, there are multiple preparation methods and fixatives for cytology. Our objective was to investigate the effect of different common fixatives on the immunoreactivity of pleural effusion CBs with metastatic lung adenocarcinomas.

METHODS

This prospective study included 24 malignant pleural effusions from different patients with lung adenocarcinoma. From each case, four identical CBs were fixed in 10% neutral buffered formalin, PreservCyt, CytoLyt, and CytoRich Red (only 17 of the cases), respectively. Samples containing <100 malignant cells were excluded. All CBs were stained with thyroid transcription factor 1 (TTF-1; clones 8G7G3/1 and SPT24), napsin A, claudin 4, CEA, CK7, and epithelial cell adhesion molecule (EpCAM; clones BS14, Ber-Ep4, and MOC-31). The fraction and intensity of stained cells were evaluated.

RESULTS

Of the investigated markers, a significant difference in staining proportion was seen for TTF-1 clone 8G7G3/1 and EpCAM clone MOC-31, especially with cases being negative in CytoLyt (33.3% and 83.3% positive, respectively) and PreservCyt (62.5% and 83.3%) whereas being positive in CytoRich Red (76.5% and 94.1%) and formalin (both 95.8%). A significantly weaker intensity of staining was seen for all alcohol-based fixatives compared to formalin for TTF-1 clone 8G7G3/1, napsin A, and EpCAM clone MOC-31, whereas EpCAM clone Ber-Ep4 was significantly weaker only in PreservCyt compared with formalin.

CONCLUSIONS

Immunocytochemical expression and concordance with formalin-fixed CBs differ depending on the used fixative as well as the antibody and clone, warranting investigation of the reliability of each biomarker for non-formalin-fixed cytology.

Principles of Analytic Validation of Immunohistochemical Assays: Guideline Update

CONTEXT.—

In 2014, the College of American Pathologists developed an evidence-based guideline to address analytic validation of immunohistochemical assays. Fourteen recommendations were offered. Per the National Academy of Medicine standards for developing trustworthy guidelines, guidelines should be updated when new evidence suggests modifications.

OBJECTIVE.—

To assess evidence published since the release of the original guideline and develop updated evidence-based recommendations.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and update the original guideline recommendations using the Grading of Recommendations Assessment, Development and Evaluation approach.

RESULTS.—

Two strong recommendations, 1 conditional recommendation, and 12 good practice statements are offered in this updated guideline. They address analytic validation or verification of predictive and nonpredictive assays, and recommended revalidation procedures following changes in assay conditions.

CONCLUSIONS.—

While many of the original guideline statements remain similar, new recommendations address analytic validation of assays with distinct scoring systems, such as programmed death receptor-1 and analytic verification of US Food and Drug Administration approved/cleared assays; more specific guidance is offered for validating immunohistochemistry performed on cytology specimens.

Consistency Analysis of Programmed Death Ligand 1 Expression in Non-Small Cell Lung Cancer Between Pleural Effusion and Matched Primary Lung Cancer Tissues by Immunohistochemical Double Staining

In clinical practice, programmed death ligand 1 (PD-L1) detection is prone to nonspecific staining due to the complex cellular composition of pleural effusion smears. In this study, diaminobenzidine (DAB) and 3-amino-9-ethylcarbazole (AEC) immunohistochemistry double staining was performed to investigate PD-L1 expression in tumor cells from malignant pleural effusion (MPE). MPE was considered as a metastasis in non-small cell lung cancer patients; thus, the heterogeneity between metastatic and primary lung cancer was revealed as well. Ninety paired specimens of MPE cell blocks and matched primary lung cancer tissues from non-small cell lung cancer patients were subjected to PD-L1 and thyroid transcription factor-1(TTF-1)/p63 immunohistochemistry double staining. Two experienced pathologists independently evaluated PD-L1 expression using 3 cutoffs (1%, 10%, and 50%). PD-L1 expression in MPE was strongly correlated with that in matched primary lung cancer tissues (R = 0.813; P < .001). Using a 4-tier scale (cutoffs: 1%, 10%, and 50%), the concordance was 71.1% (Cohen's κ = .534). Using a 2-tier scale, the concordance was 75.6% (1%, Cohen's κ = 0.53), 78.9% (10%, Cohen's κ = 0.574), and 95.6% (50%, Cohen's κ = 0.754). The rates of PD-L1 positivity in MPE (56.7%) were higher than that in lung tissues (32.2%). All 27 discordant cases had higher scores in MPE. The double-staining method provided superior identification of PD-L1-positive tumor cells on a background with nonspecific staining. In conclusion, PD-L1 expression was moderately concordant between metastatic MPE cell blocks and matched primary lung carcinoma tissues, with variability related to tumor heterogeneity. MPE should be considered to detect PD-L1 when histological specimens are unattainable, especially when PD-L1 expression is >50%. PD-L1 positivity rates were higher in MPE. Double staining can improve PD-L1 detection by reducing false-negative/positive results.

Accuracy of Cytologic vs Histologic Specimens for Assessment of Programmed Cell Death Ligand-1 Expression in Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Programmed cell death ligand-1 (PD-L1) expression on tumor cells, evaluated by immunohistochemistry, guides the use of immunotherapy in advanced non-small cell lung cancer (NSCLC).

RESEARCH QUESTION

What is the sensitivity and specificity of PD-L1 testing performed in cytologic vs paired histologic specimens in patients with NSCLC?

STUDY DESIGN AND METHODS

The MEDLINE, Embase, Web of Science, and Cochrane Library databases were searched through June 1, 2021. The primary outcome was pooled sensitivity and specificity of PD-L1 testing performed on cytologic specimens compared with the reference standard of histologic specimens, analyzed at the PD-L1 expression cutoffs (tumor proportion score) ≥ 1% and ≥ 50%. Pooled sensitivity and specificity, and associated 95% CIs, were estimated using bivariate generalized linear mixed models.

RESULTS

Twenty-six articles were included, encompassing a total of 1,064 pairs of histology specimens and cytology cell blocks, and 267 pairs of histology specimens and direct smears. Among these, 946 paired specimens were acquired without interval treatment between the collection of histology and cytology samples. The pooled sensitivity and specificity of cytology specimens compared with paired histology specimens at the PD-L1 expression cutoff ≥ 1% were 0.84 (95% CI, 0.77-0.89) and 0.88 (95% CI, 0.82-0.93), respectively, whereas the pooled sensitivity and specificity at cutoff ≥ 50% were 0.78 (95% CI, 0.69-0.86) and 0.94 (95% CI, 0.91-0.96), respectively. When only paired specimens acquired without interval treatment were considered, the pooled sensitivity and specificity of cytology specimens at PD-L1 expression cutoff ≥ 1% were 0.84 (95% CI, 0.76-0.90) and 0.89 (95% CI, 0.82-0.94), respectively, whereas the pooled sensitivity and specificity at cutoff ≥ 50% were 0.80 (95% CI, 0.71-0.89) and 0.94 (95% CI, 0.91-0.96), respectively.

INTERPRETATION

Cytologic specimens provide an accurate assessment of PD-L1 expression in most patients with NSCLC, at both ≥ 1% and ≥ 50% cutoffs, when compared with histologic specimens.

TRIAL REGISTRATION

PROSPERO; No.: CRD42020153279; URL: https://www.crd.york.ac.uk/prospero/.

PD-L1 (22C3) Expression Correlates with Clinical and Molecular Features of Lung Adenocarcinomas in Cytological Samples

INTRODUCTION

PD-L1 expression is the most widely used predictive marker for immune checkpoint inhibitor (ICI) therapy in patients with lung adenocarcinoma. However, the current understanding of the association between PD-L1 expression and treatment response is suboptimal. A significant percentage of patients have only a cytological specimen available for clinical management. Therefore, it is relevant to examine the impact of molecular features on PD-L1 expression in cytological samples and how it might correlate with a therapeutic response.

METHODS

We evaluated patients diagnosed with adenocarcinoma of the lung who had both in-house targeted next-generation sequencing analysis and paired PD-L1 (22C3) immunohistochemical staining performed on the same cell blocks. We explored the association between molecular features and PD-L1 expression. In patients who underwent ICIs therapy, we assessed how a specific gene mutation impacted a therapeutic response.

RESULTS

145 patients with lung adenocarcinoma were included in this study. PD-L1-high expression was found to be more common in pleural fluid than in other sample sites. Regional lymph node samples showed a higher proportion of PD-L1-high expression (29%) compared with lung samples (6%). The predictive value of PD-L1 expression was retained in cytological samples. Mutations in KRAS were also associated with a PD-L1-high expression. However, tumors with TP53 or KRAS mutations showed a lower therapy response rate regardless of the PD-L1 expression.

CONCLUSION

Cytological samples maintain a predictive value for PD-L1 expression in patients with lung adenocarcinoma as regards the benefit of ICI treatment. Specific molecular alterations additionally impact PD-L1 expression and its predictive value.

Cytological Samples: An Asset for the Diagnosis and Therapeutic Management of Patients with Lung Cancer

BACKGROUND

Lung cancer has become the leading cause of cancer death for men and women. Most patients are diagnosed at an advanced stage when surgery is no longer a therapeutic option. At this stage, cytological samples are often the less invasive source for diagnosis and the determination of predictive markers. We assessed the ability of cytological samples to perform diagnosis, and to establish molecular profile and PD-L1 expression, which are essential for the therapeutic management of patients.

METHODS

We included 259 cytological samples with suspected tumor cells and assessed the ability to confirm the type of malignancy by immunocytochemistry. We summarized results of molecular testing by next generation sequencing (NGS) and PD-L1 expression from these samples. Finally, we analyzed the impact of these results in the patient management.

RESULTS

Among the 259 cytological samples, 189 concerned lung cancers. Of these, immunocytochemistry confirmed the diagnosis in 95%. Molecular testing by NGS was obtained in 93% of lung adenocarcinomas and non-small cell lung cancer. PD-L1 results were obtained in 75% of patients tested. The results obtained with cytological samples led to a therapeutic decision in 87% of patients.

CONCLUSION

Cytological samples are obtained by minimally invasive procedures and can provide enough material for the diagnosis and therapeutic management in lung cancer patients.

PD-L1 testing by immunohistochemistry in immuno-oncology

Immunotherapy, based on immune checkpoint inhibitors targeting the Programmed cell death ligand 1 (PD-L1) and/or Programmed Death Receptor 1 (PD-1), has substantially improved the outcomes of patients with various cancers. However, only ~30% of patients benefit from immune checkpoint inhibitors. Tumor PD-L1 expression, assessed by immunohistochemistry, is the most widely validated and used predictive biomarker to guide the selection of patients for immune checkpoint inhibitors. PD-L1 assessment may be challenging due to the necessity for different companion diagnostic assays for required specific immune checkpoint inhibitors and a relatively high level of inter-assay variability in terms of performance and cutoff levels. In this review, we discuss the role of PD-L1 immunohistochemistry as a predictive test in immunotherapy (immuno-oncology), highlight the complexity of the PD-L1 testing landscape, discuss various preanalytical, analytical and clinical issues that are associated with PD-L1 assays, and provide some insights into optimization of PD-L1 as a predictive biomarker in immuno-oncology.

Case report: A case of acute mastitis associated with reactive cutaneous capillary endothelial proliferation after camrelizumab treatment: A new immune-related adverse event

Lung cancer is a malignant tumor with the highest morbidity and mortality rate worldwide, and it seriously endangers human health. In recent years, immunotherapy has been widely used in lung cancer and has achieved great benefits, especially the application of promoting antitumor immune defense. However, immune-related adverse events (irAEs) caused by immune checkpoint inhibitors have received increasing attention, which largely limits their use. We report the first case of new acute mastitis caused by anti-PD1 inhibitors due to lung adenocarcinoma. A 65-year-old female patient came to our hospital for treatment with cough and shortness of breath for one month. Chest CT showed that the malignant tumor in the lower lobe of the right lung with pleural effusion had metastasized to many places, and then pleural effusion was taken for pathological examination. Pathological examination indicated that the pleural fluid originated from lung adenocarcinoma. Subsequently, the patient received platinum-containing dual-agent chemotherapy (carboplatin and pemetrexed disodium) combined with immunotherapy (camrelizumab). During treatment, the patient developed known adverse events and unreported acute mastitis. After stopping camrelizumab, the patient’s mastitis gradually improved. Our case shows that acute mastitis might be a new adverse event after the use of camrelizumab. Since this new adverse event has not been reported, we hope that oncology medical workers can obtain insight from our case and use it as a reference for the identification and management of irAEs.

PD-L1 Expression in Non-Small Cell Lung Cancer Specimens: Association with Clinicopathological Factors and Molecular Alterations

Immune checkpoint inhibitors (ICI) targeting programmed cell death-1 or its ligand (PD-L1) have improved outcomes in non-small cell lung cancer (NSCLC). High tumor PD-L1 expression, detected by immunohistochemistry (IHC) typically on formalin-fixed paraffin-embedded (FFPE) histological specimens, is linked to better response. Following our previous investigation on PD-L1 in cytological samples, the aim of this study was to further explore the potential impacts of various clinicopathological and molecular factors on PD-L1 expression. Two retrospective NSCLC cohorts of 1131 and 651 specimens, respectively, were investigated for PD-L1 expression (<1%/1−49%/≥50%), sample type, sample site, histological type, and oncogenic driver status. In both cohorts, PD-L1 was positive (≥1%) in 55% of the cases. Adenocarcinomas exhibited lower PD-L1 expression than squamous cell carcinomas (p < 0.0001), while there was no difference between sample types, tumor locations, or between the two cohorts in multivariate analysis (all p ≥ 0.28). Mutational status correlated significantly with PD-L1 expression (p < 0.0001), with the highest expression for KRAS-mutated cases, the lowest for EGFR-mutated, and the KRAS/EGFR wild-type cases in between. There was no difference in PD-L1 levels between different prevalent KRAS mutations (all p ≥ 0.44), while mucinous KRAS-mutated adenocarcinomas exhibited much lower PD-L1 expression than non-mucinous (p < 0.0001). Our data indicate that cytological and histological specimens are comparable for PD-L1 evaluation. Given the impact of KRAS mutations and the mucinous growth pattern on PD-L1 expression, these factors should be further investigated in studies on ICI response.

Factors Influencing Concordance of PD-L1 Expression between Biopsies and Cytological Specimens in Non-Small Cell Lung Cancer

PD-L1 expression assessed by immunohistochemical staining is used for the selection of immunotherapy in non-small cell lung cancer (NSCLC). Appropriate validation of PD-L1 expression in cytology specimens is important as cytology is often the only diagnostic material in NSCLC. In a previous study comprising two different cohorts of paired biopsies and cytological specimens, we found a fairly good cyto-histological correlation of PD-L1 expression in one, whereas only a moderate correlation was found in the other cohort. Therefore, that cohort with additional new cases was now further investigated for the impact of preanalytical factors on PD-L1 concordance in paired biopsies and cytological specimens. A total of 100 formalin-fixed paraffin-embedded cell blocks from 19 pleural effusions (PE), 17 bronchial brushes (BB), and 64 bronchoalveolar lavage (BAL) and concurrent matched biopsies from 80 bronchial biopsies and 20 transthoracic core biopsies from NSCLC patients were stained using the PD-L1 28-8 assay. Using the cutoffs ≥1%, ≥5%, ≥10%, and ≥50% positive tumour cells, the overall agreement between histology and cytology was 77-85% (κ 0.51-0.70) depending on the applied cutoff value. The concordance was better for BALs (κ 0.53-0.81) and BBs (κ 0.55-0.85) than for PEs (κ -0.16-0.48), while no difference was seen for different types of biopsies or histological tumour type. A high number of tumour cells (>500) in biopsies was associated with better concordance at the ≥50% cutoff. In conclusion, the study results suggest that PEs may be less suitable for evaluation of PD-L1 due to limited cyto-histological concordance, while a high amount of tumour cells in biopsies may be favourable when regarding cyto-histological PD-L1 concordance.