Aligning digital CD8+scoring and targeted next-generation sequencing with programmed death ligand 1 expression: a pragmatic approach in early-stage squamous cell lung carcinoma

Assessment of PD-L1 expression and tumour infiltrating lymphocytes in early-stage non-small cell lung carcinoma with artificial intelligence algorithms

AIMS

To study programmed death ligand 1 (PD-L1) expression and tumour infiltrating lymphocytes (TILs) in patients with early-stage non-small cell lung carcinoma (NSCLC) with artificial intelligence (AI) algorithms.

METHODS

The study included samples from 50 early-stage NSCLCs. PD-L1 immunohistochemistry (IHC) stained slides (clone SP263) were scored manually and with two different AI tools (PathAI and Navify Digital Pathology) by three pathologists. TILs were digitally assessed on H&E and CD8 IHC stained sections with two different algorithms (PathAI and Navify Digital Pathology, respectively). The agreement between observers and methods for each biomarker was analysed. For PD-L1, the turn-around time (TAT) for manual versus AI-assisted scoring was recorded.

RESULTS

Agreement was higher in tumours with low PD-L1 expression regardless of the approach. Both AI-powered tools identified a significantly higher number of cases equal or above 1% PD-L1 tumour proportion score as compared with manual scoring (p=0.00015), a finding with potential therapeutic implications. Regarding TAT, there were significant differences between manual scoring and AI use (p value <0.0001 for all comparisons). The total TILs density with the PathAI algorithm and the total density of CD8+ cells with the Navify Digital Pathology software were significantly correlated (τ=0.49 (95% CI 0.37, 0.61), p value<0.0001).

CONCLUSIONS

This preliminary study supports the use of AI algorithms for the scoring of PD-L1 and TILs in patients with NSCLC.

Programmed Death Ligand-1 and Tumor Mutation Burden Testing of Patients With Lung Cancer for Selection of Immune Checkpoint Inhibitor Therapies: Guideline From the College of American Pathologists, Association for Molecular Pathology, International Association for the Study of Lung Cancer, Pulmonary Pathology Society, and LUNGevity Foundation

CONTEXT.—

Rapid advancements in the understanding and manipulation of tumor-immune interactions have led to the approval of immune therapies for patients with non-small cell lung cancer. Certain immune checkpoint inhibitor therapies require the use of companion diagnostics, but methodologic variability has led to uncertainty around test selection and implementation in practice.

OBJECTIVE.—

To develop evidence-based guideline recommendations for the testing of immunotherapy/immunomodulatory biomarkers, including programmed death ligand-1 (PD-L1) and tumor mutation burden (TMB), in patients with lung cancer.

DESIGN.—

The College of American Pathologists convened a panel of experts in non-small cell lung cancer and biomarker testing to develop evidence-based recommendations in accordance with the standards for trustworthy clinical practice guidelines established by the National Academy of Medicine. A systematic literature review was conducted to address 8 key questions. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, recommendations were created from the available evidence, certainty of that evidence, and key judgments as defined in the GRADE Evidence to Decision framework.

RESULTS.—

Six recommendation statements were developed.

CONCLUSIONS.—

This guideline summarizes the current understanding and hurdles associated with the use of PD-L1 expression and TMB testing for immune checkpoint inhibitor therapy selection in patients with advanced non-small cell lung cancer and presents evidence-based recommendations for PD-L1 and TMB testing in the clinical setting.

The effect of neoadjuvant therapy on PD-L1 expression and CD8+lymphocyte density in non-small cell lung cancer

PD-L1 expression is the routine clinical biomarker for the selection of patients to receive immunotherapy in non-small cell lung cancer (NSCLC). However, the application and best timing of immunotherapy in the resectable setting is still under investigation. We aimed to study the effect of chemotherapy on PD-L1 expression and tumor infiltrating lymphocytes (TILs), which is to date still poorly understood. Our retrospective, single-centre neoadjuvant cohort comprised 96 consecutive patients with NSCLC resected 2000-2016 after neoadjuvant therapy, including paired diagnostic chemo-naïve specimens in 53 cases. A biologically matched surgical cohort of 114 primary resected cases was included. PD-L1 expression, CD8 + TILs density and tertiary lymphoid structures were assessed on whole slides and correlated with clinico-pathological characteristics and survival. Seven/53 and 12/53 cases had lower respectively higher PD-L1 expressions after neoadjuvant therapy. Most cases (n = 34) showed no changes in PD-L1 expression, the majority of these harboring PD-L1 < 1% in both samples (21/34 [61.8%]). Although CD8 + TILs density was significantly higher after chemotherapy (p = 0.031) in resections compared to diagnostic biopsies, this might be due to sampling and statistical bias. No difference in PD-L1 expression or CD8 + TILs density was detected when comparing the neoadjuvant and surgical cohort. In univariable analyses, higher CD8 + TILs density, higher numbers of tertiary lymphoid structures but not PD-L1 expression were significantly associated with longer survival. Increased PD-L1 expression after neoadjuvant chemotherapy was not significantly associated with shorter 5-year survival, but the number of cases was very low. In multivariable analysis, only pT category and age remained independent prognostic factors. In summary, PD-L1 expression was mostly unchanged after neoadjuvant chemotherapy compared to diagnostic biopsies. The sample size of cases with changed PD-L1 expression was too small to draw conclusions on any prognostic value.

Analytical Concordance of PD-L1 Assays Utilizing Antibodies From FDA-Approved Diagnostics in Advanced Cancers: A Systematic Literature Review

PURPOSE

Four programmed death ligand 1 (PD-L1) immunohistochemistry assays (28-8, 22C3, SP263, and SP142) have been approved for use by the US Food and Drug Administration (FDA). Analytical concordance between these assays has been evaluated in multiple studies. This systematic review included studies that investigated the analytical concordance of immunohistochemistry assays utilizing two or more PD-L1 antibodies from FDA-approved diagnostics for evaluation of PD-L1 expression on tumor or immune cells across a range of tumor types and algorithms.

METHODS

Literature searches were conducted in MEDLINE (via PubMed) and EMBASE to identify studies published between January 1, 2010, and March 31, 2019, that evaluated analytical concordance between two or more assays based on antibodies from FDA-approved assays. Proceedings of key oncology and pathology congresses that took place between January 2016 and March 2019 were searched for abstracts of studies evaluating PD-L1 assay concordance.

RESULTS

A total of 42 studies across a range of tumor types met the selection criteria. Concordance between 28-8-, 22C3-, and SP263-based assays in lung cancer, urothelial carcinoma, and squamous cell carcinoma of the head and neck was high when used to assess PD-L1 expression on tumor cells (TCs). SP142-based assays had overall low concordance with other approved assays when used to assess PD-L1 expression on TCs. Analytical concordance for assessment of PD-L1 expression on immune cells was variable and generally lower than for PD-L1 expression on TCs.

CONCLUSION

A large body of evidence supports the potential interchangeability of 28-8-, 22C3-, and SP263-based assays for the assessment of PD-L1 expression on TCs in lung cancer. Further studies are required in tumor types for which less evidence is available.

Immune Checkpoint Inhibitors in Urothelial Carcinoma: Recommendations for Practical Approaches to PD-L1 and Other Potential Predictive Biomarker Testing

Simple Summary

The predominant histologic type of bladder cancer is urothelial carcinoma (UC). Programmed cell death-ligand 1 (PD-L1) expression levels in UC tumors help clinicians determine which patients are more likely to respond to immuno-oncology (IO) therapies; as such, the harmonization of PD-L1 testing in evaluating patients is increasingly important. A series of international workshops, involving renowned pathologists and oncologists, were held to develop best practice approaches to PD-L1 testing in UC. It was agreed that robust control of analytical standards is required to obtain quality PD-L1 results and that interpretation and reporting of PD-L1 require clear inter-clinician communication. Recommendations for the best practices for PD-L1 testing in UC are provided. A PD-L1 test request form for pathology laboratories was also developed and included here, encouraging communication between clinicians and pathologists, and ensuring fast and high-quality test results. Novel biomarkers being evaluated for immuno-oncology agents in UC are also briefly discussed.

Abstract

Immuno-oncology (IO) agents (anti–programmed cell death 1 (PD-1) and anti–programmed cell death-ligand 1 (PD-L1)) are approved as first- and second-line treatments for metastatic UC. PD-L1 expression levels in UC tumors help clinicians determine which patients are more likely to respond to IO therapies. Assays for approved IO agents use different antibodies, immunohistochemical protocols, cutoffs (defining “high” vs. “low” PD-L1 expression), and scoring algorithms. The robust control of pre-analytical and analytical standards is needed to obtain high-quality PD-L1 results. To better understand the status and perspectives of biomarker-guided patient selection for anti–PD-1 and anti–PD-L1 agents in UC, three workshops were held from December 2018 to December 2019 in Italy, Malaysia, and Spain. The primary goal was to develop recommendations for best practice approaches to PD-L1 testing in UC. Recommendations pertaining to the interpretation and reporting of the results of PD-L1 assays from experienced pathologists and oncologists from around the globe are included. A test request form for pathology laboratories was developed as a critical first step for oncologists/urologists to encourage communication between clinicians and pathologists, ensuring fast and high-quality test results. In this era of personalized medicine, we briefly discuss novel biomarkers being evaluated for IO agents in UC.

[Updated guidelines for predictive biomarker testing in advanced non-small-cell lung cancer: A National Consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology]

In 2011, the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP) initiated a joint project to establish guidelines for biomarker testing in patients with advanced non-small-cell lung cancer based on the information available at the time. As this field is constantly evolving, these guidelines were updated in 2012 and 2015 and now in 2019. Current evidence suggests it should be mandatory to test all patients with this kind of advanced lung cancer for EGFR and BRAF mutations, ALK and ROS1 rearrangements and PD-L1 expression. The growing need to study other emerging biomarkers has promoted the routine use of massive sequencing (next-generation sequencing, NGS). However, the coordination of every professional involved and the prioritisation of the most suitable tests and technologies for each case remain a challenge.

Selected highlights of the 2019 Pulmonary Pathology Society Biennial Meeting: PD-L1 test harmonization studies

Immune checkpoint inhibitors (ICI) including programmed death 1 (PD-1) inhibitors, such as nivolumab and pembrolizumab, or programmed death ligand 1 (PD-L1) inhibitors, such as atezolizumab and durvalumab, have recently emerged in advanced stage lung cancer as new standards of care. They are now indicated in first- line and second- or later-line treatment of metastatic or locally-advanced stage III non-small cell lung cancer (NSCLC), as well as for metastatic small cell lung cancer (SCLC), as single agent immunotherapy or in combination with chemotherapy. Four PD-L1 immunohistochemistry (IHC) assays have been established and validated in randomized trials, each for a specific ICI. They use different primary monoclonal antibodies, platforms and detection systems, as well as different scoring systems to assess PD-L1 expression either by tumor cells (TCs) and/or by infiltrating immune cells (ICs). Most studies have shown a close analytical performance of three of these clinically-validated standardized assays, but their use restricted to dedicated platforms, which are not all available in most laboratories, questions their applicability. In addition, the relative high costs of the assays have led to the development of in-house protocols in many pathology laboratories. Their use in clinical practice to assess the predictive value of PD-L1 expression for prescription of ICI raises the issue of their reliability and their validation as compared to standardized assays. This article discusses the main comparative studies available between LDT and assays, with clear evidence that LDT can reach a performance equivalent to the trial-validated assays. The requirements are an adequate validation as compared to an appropriate standard, and the participation to external quality assurance programs and training programs for PD-L1 IHC assessment for pathologists.

Comparability of PD-L1 immunohistochemistry assays for non-small-cell lung cancer: a systematic review

Programmed cell death ligand 1 (PD‐L1) immunohistochemistry is used to determine which patients with advanced non‐small‐cell lung cancer (NSCLC) respond best to treatment with PD‐L1 inhibitors. For each inhibitor, a unique immunohistochemical assay was developed. This systematic review gives an up‐to‐date insight into the comparability of standardised immunohistochemical assays and laboratory‐developed tests (LDTs), focusing specifically on tumour cell (TC) staining and scoring. A systematic search was performed identifying publications that assessed interassay, interobserver and/or interlaboratory concordance of PD‐L1 assays and LDTs in tissue of NSCLC patients. Of 4294 publications identified through the systematic search, 27 fulfilled the inclusion criteria and were of sufficient methodological quality. Studies assessing interassay concordance found high agreement between assays 22C3, 28‐8 and SP263 and properly validated LDTs, and lower concordance for comparisons involving SP142. A decrease in concordance, however, is seen with use of cut‐offs, which hampers interchangeability of PD‐L1 immunohistochemistry assays and LDTs. Studies assessing interobserver concordance found high agreement for all assays and LDTs, but lower agreement with use of a 1% cut‐off. This may be problematic in clinical practice, as discordance between pathologists at this cut‐off may result in some patients being denied valuable treatment options. Finally, five studies assessed interlaboratory concordance and found moderate to high agreement levels for various assays and LDTs. However, to assess the actual existence of interlaboratory variation in PD‐L1 testing and PD‐L1 positivity in clinical practice, studies using real‐world clinical pathology data are needed.

PD-L1 Testing for Lung Cancer in 2019: Perspective From the IASLC Pathology Committee

The recent development of immune checkpoint inhibitors (ICIs) has led to promising advances in the treatment of patients with NSCLC and SCLC with advanced or metastatic disease. Most ICIs target programmed cell death protein 1 (PD-1) or programmed death ligand 1 (PD-L1) axis with the aim of restoring antitumor immunity. Multiple clinical trials for ICIs have evaluated a predictive value of PD-L1 protein expression in tumor cells and tumor-infiltrating immune cells (ICs) by immunohistochemistry (IHC), for which different assays with specific IHC platforms were applied. Of those, some PD-L1 IHC assays have been validated for the prescription of the corresponding agent for first- or second-line treatment. However, not all laboratories are equipped with the dedicated platforms, and many laboratories have set up in-house or laboratory-developed tests that are more affordable than the generally expensive clinical trial-validated assays. Although PD-L1 IHC test is now deployed in most pathology laboratories, its appropriate implementation and interpretation are critical as a predictive biomarker and can be challenging owing to the multiple antibody clones and platforms or assays available and given the typically small size of samples provided. Because many articles have been published since the issue of the IASLC Atlas of PD-L1 Immunohistochemistry Testing in Lung Cancer, this review by the IASLC Pathology Committee provides updates on the indications of ICIs for lung cancer in 2019 and discusses important considerations on preanalytical, analytical, and postanalytical aspects of PD-L1 IHC testing, including specimen type, validation of assays, external quality assurance, and training.

Updated guidelines for predictive biomarker testing in advanced non-small-cell lung cancer: a National Consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology

In 2011 the Spanish Society of Medical Oncology (SEOM) and the Spanish Society of Pathology (SEAP) started a joint project to establish guidelines on biomarker testing in patients with advanced non-small-cell lung cancer (NSCLC) based on current evidence. As this field is constantly evolving, these guidelines have been updated, previously in 2012 and 2015 and now in 2019. Current evidence suggests that the mandatory tests to conduct in all patients with advanced NSCLC are for EGFR and BRAF mutations, ALK and ROS1 rearrangements and PD-L1 expression. The growing need to study other emerging biomarkers has promoted the routine use of massive sequencing (next-generation sequencing, NGS). The coordination of every professional involved and the prioritisation of the most suitable tests and technologies for each case remains a challenge.

ESMO recommendations on the standard methods to detect NTRK fusions in daily practice and clinical research

BACKGROUND

NTRK1, NTRK2 and NTRK3 fusions are present in a plethora of malignancies across different histologies. These fusions represent the most frequent mechanism of oncogenic activation of these receptor tyrosine kinases, and biomarkers for the use of TRK small molecule inhibitors. Given the varying frequency of NTRK1/2/3 fusions, crucial to the administration of NTRK inhibitors is the development of optimal approaches for the detection of human cancers harbouring activating NTRK1/2/3 fusion genes.

MATERIALS AND METHODS

Experts from several Institutions were recruited by the European Society for Medical Oncology (ESMO) Translational Research and Precision Medicine Working Group (TR and PM WG) to review the available methods for the detection of NTRK gene fusions, their potential applications, and strategies for the implementation of a rational approach for the detection of NTRK1/2/3 fusion genes in human malignancies. A consensus on the most reasonable strategy to adopt when screening for NTRK fusions in oncologic patients was sought, and further reviewed and approved by the ESMO TR and PM WG and the ESMO leadership.

RESULTS

The main techniques employed for NTRK fusion gene detection include immunohistochemistry, fluorescence in situ hybridization (FISH), RT-PCR, and both RNA-based and DNA-based next generation sequencing (NGS). Each technique has advantages and limitations, and the choice of assays for screening and final diagnosis should also take into account the resources and clinical context.

CONCLUSION

In tumours where NTRK fusions are highly recurrent, FISH, RT-PCR or RNA-based sequencing panels can be used as confirmatory techniques, whereas in the scenario of testing an unselected population where NTRK1/2/3 fusions are uncommon, either front-line sequencing (preferentially RNA-sequencing) or screening by immunohistochemistry followed by sequencing of positive cases should be pursued.

[Protein expression of PD-L1 and clinico-pathological data in a cohort of 53 patients with resectable non small cell lung cancer (NSCLC). Concordance between clones (22C3 and 28-8) and observers. Correlation and prognostic value of clinico-pathological data]

INTRODUCTION

85% of lung cancers are non-small cell carcinomas (NSCLC), the majority of which are diagnosed in an advanced stage. Immunotherapy has changed the treatment pattern for these tumors and created the need to find a marker for patient selection. Although not ideal, PD-L1 is the biomarker currently used in clinical practice.

MATERIAL AND METHODS

Retrospective review by two pathologists of 53 cases of NSCLC from 2005 to 2007 in Hospital Universitario La Paz, using the WHO 2015 classification studying PD-L1 with clones 22C3 and 28-8. The consistency between observers and clones was assessed and all data studied were correlated with survival rates.

RESULTS

We found a prevalence of PD-L1 expression in tumor cells (TC) similar to that previously reported in the literature and a very good consistency between clones in the evaluation of TC and immune cells (ICC 0.99-0.93, p<.001). Interobserver concordance was very good in the evaluation of TC (ICC 0.902, 95% CI: 0.836-0.942, p<.001 for clone 22C3 and ICC 0.927, 95% CI: 0.877-0.957, p<.001 for clone 28-8) and poor for immune cells (ICC of 0.413, 95% CI: 0.163-0.613, p=.001 with clone 22C3 and ICC of 0.313, 95% CI: 0.053-0.534, p=.010 with clone 28-8). Subtype and histological grade were the only variables related to prognosis.

CONCLUSIONS

The clones of PD-L1 22C3 and 28-8 are equivalent and there is good interobserver consistency in the evaluation of TC but not in immune cells.

Bladder cancer, a unique model to understand cancer immunity and develop immunotherapy approaches

With the mechanistic understanding of immune checkpoints and success in checkpoint blockade using antibodies for the treatment of certain cancers, immunotherapy has become one of the hottest areas in cancer research, with promise of long‐lasting therapeutic effect. Currently, however, only a proportion of cancers have a good response to checkpoint inhibition immunotherapy. Better understanding of the cancer response and resistance mechanisms is essential to fully explore the potential of immunotherapy to cure the majority of cancers. Bladder cancer, one of the most common and aggressive malignant diseases, has been successfully treated both at early and advanced stages by different immunotherapeutic approaches, bacillus Calmette–Guérin (BCG) intravesical instillation and anti‐PD‐1/PD‐L1 immune checkpoint blockade, respectively. Therefore, it provides a good model to investigate cancer immune response mechanisms and to improve the efficiency of immunotherapy. Here, we review bladder cancer immunotherapy with equal weight on BCG and anti‐PD‐1/PD‐L1 therapies and demonstrate why and how bladder cancer can be used as a model to study the predictors and mechanisms of cancer immune response and shine light on further development of immunotherapy approaches and response predictive biomarkers to improve immunotherapy of bladder cancer and other malignancies. We review the success of BCG and anti‐PD‐1/PD‐L1 treatment of bladder cancer, the underlying mechanisms and the therapeutic response predictors, including the limits to our knowledge. We then highlight briefly the adaptation of immunotherapy approaches and predictors developed in other cancers for bladder cancer therapy. Finally, we explore the potential of using bladder cancer as a model to investigate cancer immune response mechanisms and new therapeutic approaches, which may be translated into immunotherapy of other human cancers. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

PD-L1 expression in non-small cell lung cancer: evaluation of the diagnostic accuracy of a laboratory-developed test using clone E1L3N in comparison with 22C3 and SP263 assays

Different studies have evaluated the comparability of various immunohistochemical assays for PD-L1 expression evaluation, with contrasting results. Besides the important issues related to analytic performance and comparability of validated assays, not all platforms are available in all laboratories; moreover, standardized assays are very expensive, and funding for PD-L1 testing is hard to obtain, especially in the research setting. One of the most widely used and inexpensive PD-L1 clones is E1L3N (Cell Signaling Technology, Danvers, MA), which is labeled for research use only. In this work, we wanted to further study and validate in a larger cohort the analytical performance of E1L3N clone on Ventana platform (Ventana Medical Systems, Tucson, AZ) and its comparability with assays SP263 and 22C3 run onto their dedicated platforms. Serial sections of tissue microarrays built from 165 cases of resected lung cancer were stained for E1L3N onto Ventana platform following a previously reported protocol and for 22C3 and SP263 assays onto their respective platforms following manufacturer's instructions. Overall, we found very high concordance when comparing E1L3N with SP263 at both 1% and 50% cutoffs. Lower concordance was found between E1L3N and 22C3 at both cutoffs; however, 100% sensitivity was found for E1L3N compared with both SP263 and 22C3 at 50% cutoff. Given the 100% sensitivity at 50% cutoff demonstrated by E1L3N in comparison with both SP263 and 22C3 and therefore the lack of false-negative cases, we propose an algorithm for PD-L1 testing in NSCLC when considering pembrolizumab as first-line therapy.

Precision immunoprofiling by image analysis and artificial intelligence

Clinical success of immunotherapy is driving the need for new prognostic and predictive assays to inform patient selection and stratification. This requirement can be met by a combination of computational pathology and artificial intelligence. Here, we critically assess computational approaches supporting the development of a standardized methodology in the assessment of immune-oncology biomarkers, such as PD-L1 and immune cell infiltrates. We examine immunoprofiling through spatial analysis of tumor-immune cell interactions and multiplexing technologies as a predictor of patient response to cancer treatment. Further, we discuss how integrated bioinformatics can enable the amalgamation of complex morphological phenotypes with the multiomics datasets that drive precision medicine. We provide an outline to machine learning (ML) and artificial intelligence tools and illustrate fields of application in immune-oncology, such as pattern-recognition in large and complex datasets and deep learning approaches for survival analysis. Synergies of surgical pathology and computational analyses are expected to improve patient stratification in immuno-oncology. We propose that future clinical demands will be best met by (1) dedicated research at the interface of pathology and bioinformatics, supported by professional societies, and (2) the integration of data sciences and digital image analysis in the professional education of pathologists.

Prognostic impact of CD8 and programmed death-ligand 1 expression in patients with resectable non-small cell lung cancer

Background

The prognostic impact of the expression of CD8 and programmed death-ligand 1 (PD-L1) has not been established in patients with resectable non-small cell lung cancer (NSCLC).

Methods

Surgical tissue specimens were obtained from 136 patients with NSCLC who underwent surgical resection. The expression levels of CD8 and PD-L1 were assessed using tissue microarrays and immunohistochemistry.

Results

The CD8-positive group showed significant increases in overall survival (OS) (median, not reached [NR] vs. 28.452 months) and relapse-free survival (RFS) (median, NR vs. 14.916 months) compared with the CD8-negative group. In contrast to CD8, the PD-L1-negative group demonstrated significant increases in OS (median, NR vs. 29.405 months) and RFS (median, 63.573 vs. 17.577 months) compared with the PD-L1-positive group. Two prognostic groups were stratified according to CD8/PD-L1 expression: group 1 (CD8-positive/PD-L1-negative) vs. group 2 (CD8/PD-L1: positive/positive, negative/negative, negative/positive). Group 1 had better OS (median, NR vs. 29.405 months) and RFS (median, NR vs. 17.577 months) than group 2. Multivariate analysis indicated that group 1 constituted an independent favourable prognostic factor for OS (hazard ratio [HR], 0.329, p = 0.001) and RFS (HR, 0.293; p < 0.001).

Conclusions

Positive CD8 and negative PD-L1 expression together may be favourable prognostic markers in resectable NSCLC.

PD-L1 immunohistochemistry for non-small cell lung carcinoma: which strategy should be adopted?

INTRODUCTION

PD-L1 detection with immunohistochemistry (IHC) is the only predictive biomarker available to date for PD-L1/PD1 immunotherapy in thoracic oncology. While many studies have been published on this biomarker, they raise a number of questions concerning mainly, (i) the type of antibody for use and its condition of utilization, (ii) the threshold to be used, (iii) the message and information to communicate to the thoracic oncologist and, (iv) the adoption of this methodology as part of the daily practices of a pathology laboratory. Areas covered: This review provides an update on the use of the different PD-L1 antibodies for IHC in the context of metastatic non-small cell lung cancer (NSCLC) and discusses their use as companion or complementary diagnostic tests. The limits of PD-L1 IHC as a predictive test, the precautions to be adopted as well as some perspectives will then be considered. Expert commentary: IHC for PD-L1 can be considered as a theranostic test, which implies providing an extremely reliable result that avoids any false positive and negative results. PD-L1 IHC requires considerable expertise and specific training of pathologists. PD-L1 IHC can be a companion or complementary diagnostic test depending on the clone employed, the molecular therapy prescribed and the indication of use.