On the relevance of a testing algorithm for the detection of ROS1-rearranged lung adenocarcinomas

Clinicopathological features and prognostic significance of pulmonary adenocarcinoma with signet ring cell components: meta-analysis and SEER analysis

Pulmonary adenocarcinoma is a common type of lung cancer that has been on the rise in recent years. Signet ring cell components (SRCC) can be present in various patterns of pulmonary adenocarcinoma, including papillary, acinar, and solid patterns. "Signet ring cell carcinoma" is a distinct subtype in the 2014 WHO classification of lung neoplasms, subsequent WHO classifications in 2015 and 2021 have deemed signet ring cells as accompanying morphological features with no clinical significance. The prognostic and clinical implications of SRCC in pulmonary adenocarcinoma remain controversial. Therefore, we conducted a meta-analysis to investigate the clinicopathological features and prognostic factors of SRCC in pulmonary adenocarcinoma. We conducted a comprehensive search in PubMed, EMBASE, and Web of Science to identify studies that examined the clinicopathological features and prognostic implications of pulmonary adenocarcinoma with SRCC. We used both fixed- and random-effects models to analyze the data and calculate the pooled hazard ratio (HR) and odds ratio (OR) with 95% confidence intervals (CIs). Additionally, we explored the prognostic significance of SRCC in pulmonary adenocarcinoma using the Surveillance, Epidemiology, and End Results (SEER) database. Our meta-analysis included 29 studies with pulmonary adenocarcinoma and SRCC components. The results showed that pulmonary adenocarcinoma with SRCC was associated with larger tumor size (OR = 1.99; 95% CI, 1.62-2.44, p < 0.001), advanced overall stage (OR = 5.18, 95% CI, 3.28-8.17, p < 0.00001) and lymph node stage (OR = 5.79, 95% CI, 1.96-17.09, p = 0.001), and worse overall survival (OS) compared to those without SRCC (HR = 1.80, 95% CI, 1.50-2.16, p < 0.00001). Analysis using the SEER dataset confirmed these findings. Our meta-analysis provides evidence that pulmonary adenocarcinoma with SRCC is associated with distinct clinicopathological features and a poorer prognosis. These findings have important implications for the management and treatment of patients. However, further studies are needed to validate these findings and explore the significance of SRCC in various subtypes of pulmonary adenocarcinoma.

The strategic roles of four enzymes in the interconnection between metabolism and oncogene activation in non-small cell lung cancer: Therapeutic implications

NSCLC is the leading cause of cancer mortality and represents a major challenge in cancer therapy. Intrinsic and acquired anticancer drug resistance are promoted by hypoxia and HIF-1α. Moreover, chemoresistance is sustained by the activation of key signaling pathways (such as RAS and its well-known downstream targets PI3K/AKT and MAPK) and several mutated oncogenes (including KRAS and EGFR among others). In this review, we highlight how these oncogenic factors are interconnected with cell metabolism (aerobic glycolysis, glutaminolysis and lipid synthesis). Also, we stress the key role of four metabolic enzymes (PFK1, dimeric-PKM2, GLS1 and ACLY), which promote the activation of these oncogenic pathways in a positive feedback loop. These four tenors orchestrating the coordination of metabolism and oncogenic pathways could be key druggable targets for specific inhibition. Since PFK1 appears as the first tenor of this orchestra, its inhibition (and/or that of its main activator PFK2/PFKFB3) could be an efficacious strategy against NSCLC. Citrate is a potent physiologic inhibitor of both PFK1 and PFKFB3, and NSCLC cells seem to maintain a low citrate level to sustain aerobic glycolysis and the PFK1/PI3K/EGFR axis. Awaiting the development of specific non-toxic inhibitors of PFK1 and PFK2/PFKFB3, we propose to test strategies increasing citrate levels in NSCLC tumors to disrupt this interconnection. This could be attempted by evaluating inhibitors of the citrate-consuming enzyme ACLY and/or by direct administration of citrate at high doses. In preclinical models, this "citrate strategy" efficiently inhibits PFK1/PFK2, HIF-1α, and IGFR/PI3K/AKT axes. It also blocks tumor growth in RAS-driven lung cancer models, reversing dedifferentiation, promoting T lymphocytes tumor infiltration, and increasing sensitivity to cytotoxic drugs.

Correlation of ROS1 (D4D6) Immunohistochemistry with ROS1 Fluorescence In Situ Hybridization Assay in a Contemporary Cohort of Pulmonary Adenocarcinomas

Sambit K. MohantyObjective  Repressor of Silencing ( ROS1 ) gene rearrangement in the lung adenocarcinomas is one of the targetable mutually exclusive genomic alteration. Fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), next-generation sequencing, and reverse transcriptase polymerase chain reaction assays are generally used to detect ROS1 gene alterations. We evaluated the correlation between ROS1 IHC and FISH analysis considering FISH as the gold standard method to determine the utility of IHC as a screening method for lung adenocarcinoma. Materials and Methods  A total of 374 advanced pulmonary adenocarcinoma patients were analyzed for ROS1 IHC on Ventana Benchmark XT platform using D4D6 rabbit monoclonal antibody. FISH assay was performed in parallel in all these cases using the Vysis ROS1 Break Apart FISH probe. Statistical Analysis  The sensitivity, specificity, positive and negative likelihood ratios, positive and negative predictive values, and accuracy were evaluated. Results  A total of 17 tumors were positive either by IHC or FISH analysis or both (true positive). Four tumors were positive by IHC (H-score range: 120-270), while negative on FISH analysis (false positive by IHC). One tumor was IHC negative, but positive by FISH analysis (false negative). The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value, and accuracy were 94.4% (confidence interval [CI]: 72.71-99.86%), 63.6% (CI: 30.79-89.07%), 2.6 (CI: 1.18-5.72), 0.09 (CI: 0.01-0.62), 80.95% (CI: 65.86-90.35%), 87.5% (CI: 49.74-98.02%), and 82.76%, respectively. Conclusion   ROS1 IHC has high sensitivity at a cost of lower specificity for the detection of ROS1 gene rearrangement. All IHC positive cases should undergo a confirmatory FISH test as this testing algorithm stands as a reliable and economic tool to screen ROS1 rearrangement in lung adenocarcinomas.

ROS1-positive non-small cell lung cancer (NSCLC): Biology, Diagnostics, Therapeutics and Resistance

ROS1 is a proto-oncogene encoding a receptor tyrosine protein kinase (RTK), homologous to the v - Ros sequence of University of Manchester tumours virus 2(UR2) sarcoma virus, whose ligands are still being investigated. ROS1 fusion genes have been identified in various types of tumours. As an oncoprotein, it promotes cell proliferation, activation and cell cycle progression by activating downstream signalling pathways, accelerating the development and progression of non-small cell lung cancer (NSCLC). Studies have demonstrated that ROS1 inhibitors are effective in patients with ROS1-positive NSCLC and are used for first-line clinical treatment. These small molecule inhibitors provide a rational therapeutic option for the treatment of ROS1-positive patients. Inevitably, ROS1 inhibitor resistance mutations occur, leading to tumours recurrence or progression. Here, we comprehensively review the identified biological properties and Differential subcellular localization of ROS1 fusion oncoprotein promotes tumours progression. We summarize recently completed and ongoing clinical trials of the classic and new ROS1 inhibitors. More importantly, we classify the complex evolving tumours cell resistance mechanisms. This review contributes to our understanding of the biological properties of ROS1 and current therapeutic advances and resistant tumours cells, and the future directions to develop ROS1 inhibitors with durable effects.

The prognostic role of PD-1, PD-L1, ALK, and ROS1 proteins expression in non-small cell lung carcinoma patients from Egypt

Background

Programmed death ligand-1 (PD-L1), anaplastic lymphoma kinase (ALK), and c-ros oncogene1 (ROS1) expression may influence the prognosis of non-small cell lung carcinoma (NSCLC). We aimed to investigate the prognostic and predictive significance of PD-1/PD-L1 along with c-ros ROS1 and ALK in NSCLC patients.

Methods

Immunohistochemistry used to identify ALK, ROS1, PD-1, and PD-L1 proteins expression as well as ROS1 rearrangement via fluorescence in situ hybridization, in 70 NSCLC patients. Results were related to clinicopathological feature, survival, and treatment response.

Results

Expression of ROS1, ALK, PD-1, and PD-L1 and ROS1-rearrangement were detected in 18.57%, 54.29%, 84.29%, 87.14%, and 15.71% of the cases, respectively. No association was found between ROS1, PD-1, and PD-L1 and any clinicopathological features, survival, or treatment outcome. ALK expression significantly associated with stage-IV and left-sided tumors. Epidermal growth factor receptor (EGFR) mutation and ALK-positive patients had significantly reduced progression-free survival than patients with wild type EGFR [HR: 1.99, 95% CI: 1.37–2.93, p < 0.001] and negative-ALK expression [HR: 1.46, 95% CI: 1.03–2.07, p = 0.03]. In multivariate analysis, lymph node metastasis, EGFR-mutations, and ALK were independent predictors of NSCLC. PD-L1 expression was significantly correlated with PD-1 but not with ROS1, ALK, or EGFR-mutation.

Conclusion

Positive ALK expression and EGFR-mutations are independent adverse predictors of NSCLC. Overexpression of PD-1/PD-L1 is not a significant prognostic marker in NSCLC patients receiving chemotherapy, making them susceptible to immunotherapy. Since PD-1/PD-L1 expression is independent to oncogenic driver mutations, future studies into specific immune checkpoint inhibitors combined with targeted therapies for individualized treatment of NSCLC is warranted.

Positive ALK expression and EGFR mutations are independent risk factors for NSCLC. Overexpression of PD-1/PD-L1 is not a significant prognostic factor in patients with NSCLC who are receiving chemotherapy, making them immunotherapy susceptible. Given that PD-1/PD-L1 expression is not dependent on oncogenic driver mutations, additional research into specific immune checkpoint inhibitors in combination with targeted therapies for the treatment of NSCLC on an individual basis is warranted.

Molecular diagnosis in non-small-cell lung cancer: expert opinion on ALK and ROS1 testing

The effectiveness of targeted therapies with tyrosine kinase inhibitors in non-small-cell lung cancer (NSCLC) depends on the accurate determination of the genomic status of the tumour. For this reason, molecular analyses to detect genetic rearrangements in some genes (ie, ALK, ROS1, RET and NTRK) have become standard in patients with advanced disease. Since immunohistochemistry is easier to implement and interpret, it is normally used as the screening procedure, while fluorescence in situ hybridisation (FISH) is used to confirm the rearrangement and decide on ambiguous immunostainings. Although FISH is considered the most sensitive method for the detection of ALK and ROS1 rearrangements, the interpretation of results requires detailed guidelines. In this review, we discuss the various technologies available to evaluate ALK and ROS1 genomic rearrangements using these techniques. Other techniques such as real-time PCR and next-generation sequencing have been developed recently to evaluate ALK and ROS1 gene rearrangements, but some limitations prevent their full implementation in the clinical setting. Similarly, liquid biopsies have the potential to change the treatment of patients with advanced lung cancer, but further research is required before this technology can be applied in routine clinical practice. We discuss the technical requirements of laboratories in the light of quality assurance programmes. Finally, we review the recent updates made to the guidelines for the determination of molecular biomarkers in patients with NSCLC.

Fifty-five months progression-free survival with crizotinib treatment in coexistence of ALK and ROS1 rearrangements in lung adenocarcinoma: an extremely rare case and review of the literature

We wanted to present a case with coexistence of anaplastic lymphoma kinase (ALK) and c-ros oncogene 1 (ROS1) rearrangements that has been in remission for a long time with crizotinib. A 62-year-old nonsmoker male patient was diagnosed with Non-small cell lung cancer. Progression developed 9 months after the treatment, and coexistence of ALK and ROS1 positivity were detected in driver mutation analysis performed with fluorescent in situ hybridization. Crizotinib 2 × 250 mg was started in November 2016. The treatment of the patient, who has been in remission for approximately 55 months since then, continues. Until recently, the use of next-generation sequencing (NGS) was not common, but the more frequent epidermal growth factor receptor, then ALK, and finally ROS1 mutation were studied in tumor tissues. Sometimes ROS1 was not studied because there was not enough tissue left. We think that this rate will increase a little more with the widespread use of NGS from now on. Showing that ALK and ROS1 are positive together, longer survivals can be obtained by choosing therapies that are responsive to both.

Updates in grading and invasion assessment in lung adenocarcinoma

The pathologic evaluation of lung adenocarcinoma, because of greater understanding of disease progression and prognosis, has become more complex. It is clear that histologic growth patterns reflect indolent and aggressive disease, resulting in clearer morphologic groups that can be the underpinning of a grading system. In addition, the progression of adenocarcinoma from a tumor that preserves alveolar architecture to one that remodels and effaces lung structure has led to criteria that reflect invasive rather than in-situ growth. While some of these are based on tumor cell growth pattern, aspects of this remodeling from desmoplasia to artifacts of lung collapse and sectioning, can lead to difficult to interpret patterns with lower reproducibility between observers. Such scenarios are examined to provide updates on new histologic concepts and to highlight ongoing problem areas.

Recent advances in lung cancer genomics: Application in targeted therapy

Genomic characterization of lung cancer has not only improved our understanding of disease biology and carcinogenesis but also revealed several therapeutic opportunities. Targeting tumor dependencies on specific genomic alterations (oncogene addiction) has accelerated the therapeutic developments and significantly improved the outcomes even in advanced stage of disease. Identification of genomic alterations predicting response to specific targeted treatment is the key to success for this "personalized treatment" approach. Availability of multiple choices of therapeutic options for specific genomic alterations highlight the importance of optimum sequencing of drugs. Multiplex gene testing has become mandatory in view of constantly increasing number of therapeutic targets and effective treatment options. Influence of genomic characteristics on response to immunotherapy further makes comprehensive genomic profiling necessary before therapeutic decision making. A comprehensive elucidation of resistance mechanisms and directed treatments have made the continuum of care possible and transformed this deadly disease into a chronic condition. Liquid biopsy-based approach has made the dynamic monitoring of disease possible and enabled treatment optimizations accordingly. Current lung cancer management is the perfect example of "precision-medicine" in clinical oncology.

Deepening the Knowledge of ROS1 Rearrangements in Non-Small Cell Lung Cancer: Diagnosis, Treatment, Resistance and Concomitant Alterations

ROS proto-oncogene 1 (ROS1) rearrangements are reported in about 1-2% of non-squamous non-small-cell lung cancer (NSCLC). After efficacy of crizotinib was demonstrated, identification of ROS1 translocations in advanced disease became fundamental to give patients the chance of specific and effective treatment. Different methods are available for detection of rearrangements, and probably the real prevalence of ROS1 rearrangements is higher than that reported in literature, as our capacity to detect gene rearrangements is improving. In particular, with next generation sequencing (NGS) techniques, we are currently able to assess multiple genes simultaneously with increasing sensitivity. This is leading to overcome the "single oncogenic driver" paradigm, and in the very near future, the co-existence of multiple drivers will probably emerge more frequently and represent a therapeutic issue. Since recently, crizotinib has been the only available therapy, but today, many other tyrosine kinase inhibitors (TKI) are emerging and seem promising both in first and subsequent lines of treatment. Indeed, novel inhibitors are also able to overcome resistance mutations to crizotinib, hypothesizing a possible sequential strategy also in ROS1-rearranged disease. In this review, we will focus on ROS1 rearrangements, dealing with diagnostic aspects, new therapeutic options, resistance issues and the coexistence of ROS1 translocations with other molecular alterations.

The 2021 WHO Classification of Lung Tumors: Impact of advances since 2015

The 2021 World Health Organisation (WHO) Classification of Thoracic Tumours was published earlier this year, with classification of lung tumors being one of the chapters. The principles remain those of using morphology first, supported by immunohistochemistry and then molecular techniques. In 2015, there was particular emphasis on using immunohistochemistry to make classification more accurate. In 2021, there is greater emphasis throughout the book on advances in molecular pathology across all tumor types. Major features within this edition are 1) broader emphasis on genetic testing than in the 2015 WHO Classification, 2) a chapter entirely dedicated to the classification of small diagnostic samples, 3) continued recommendation to document percentages of histological patterns in invasive non-mucinous adenocarcinomas, with utilization of these features to apply a formal grading system, as well as using only invasive size for T-factor size determination in part lepidic non-mucinous lung adenocarcinomas as recommended by the 8^th Edition TNM Classification, 4) recognition of spread through airspaces (STAS) as a histological feature with prognostic significance, 5) moving lymphoepithelial carcinoma to squamous cell carcinomas, 6) update on evolving concepts in lung neuroendocrine neoplasm classification, 7) recognition of bronchiolar adenoma/ciliated muconodular papillary tumor (BA/CMPT) as a new entity within the adenoma subgroup, 8) recognition of thoracic SMARCA4-deficient undifferentiated tumor, and 9) inclusion of essential and desirable diagnostic criteria for each tumor.

ROS1 rearrangements in lung adenocarcinomas are defined by diffuse strong immunohistochemical expression of ROS1

A small subset of lung adenocarcinomas harbour ROS1 gene arrangements and are amenable to tyrosine kinase inhibitor therapy. Current practice in Australia involves screening for ROS1 rearrangements in adenocarcinomas using ROS1 immunohistochemistry (IHC) followed by confirmatory molecular testing such as fluorescence in situ hybridisation (FISH), if other known genetic driver alterations are absent. The best threshold to determine ROS1 IHC positivity is not well defined, however, and this study aims to determine the optimal threshold for ROS1 IHC screening to identify ROS1-rearranged lung adenocarcinomas. A total of 177 lung adenocarcinomas tested for a ROS1 rearrangement by FISH at our institution between 2017 and 2020 due to presence of ROS1 IHC staining were included in the study. ROS1 IHC staining was assessed by scoring the staining intensity (0, 1, 2, or 3+) and multiplying by the percentage of positive cells to generate an H-score. IHC H-scores were compared with FISH. Of 177 cases, 32 (18%) were ROS1 FISH-positive and 145 (82%) were negative. FISH-positive cases had a median H-score of 300 (range 200-300; mean 290.3) and negative cases had a median H-score of 40 (range 0-300; mean 63). All FISH-positive cases showed strong and diffuse IHC positivity. Using a threshold H-score of 200, the sensitivity of identifying ROS1 rearrangements was 100% and the specificity was 95% amongst cases referred with ROS1 IHC positivity. Adenocarcinomas with a FISH-confirmed ROS1 rearrangement demonstrate diffuse, strong (2-3+) IHC staining. Cases with weak, patchy ROS1 IHC staining are not associated with ROS1 rearrangements and in these cases FISH testing is of little to no utility.

ROS1 rearrangements in non-small cell lung cancer: screening by immunohistochemistry using proportion of cells staining without intensity and excluding cases with MAPK pathway drivers improves test performance

Therapeutically actionable ROS1 rearrangements have been described in 1-3% of non-small cell lung cancer (NSCLC). Screening for ROS1 rearrangements is recommended to be by immunohistochemistry (IHC), followed by confirmation with fluorescence in situ hybridisation (FISH) or sequencing. However, in practise ROS1 IHC presents difficulties due to conflicting scoring systems, multiple clones and expression in tumours that are wild-type for ROS1. We assessed ROS1 IHC in 285 consecutive cases of NSCLC with non-squamous histology over a nearly 2-year period. IHC was scored with ROS1 clone D4D6 (n=270), clone SP384 (n=275) or both clones (n=260). Results were correlated with ROS1 break-apart FISH (n=67), ALK status (n=194), and sequence data of EGFR (n=178) and other drivers, where possible. ROS1 expression was detected in 161/285 cases (56.5%), including 13/14 ROS1 FISH-positive cases. There was no ROS1 expression in one ROS1 FISH-positive case in which sequencing detected an ALK-EML4 fusion, but not a ROS1 fusion. The other 13 ROS1 FISH-positive cases showed moderate to strong staining with both IHC clones. However, one case with a TPM3-ROS1 fusion would have been scored as negative with SP384 and D4D6 clones by some previous criteria. ROS1 expression was also detected in 58/285 cases (20.4%) that had driver mutations in genes other than ROS1. A sensitivity of 100% for detecting a ROS1 rearrangement by FISH was achieved by omitting intensity from the IHC scoring criteria and expression in >0% cells with D4D6 or in ≥50% cells with SP384. Excluding cases with driver events in any MAPK pathway gene (e.g., in ALK, EGFR, KRAS, BRAF, ERBB2 and MET) substantially reduced the number of cases proceeding to ROS1 FISH. Only 15.9% of MAPK-negative NSCLC would proceed to FISH for an IHC threshold of >0% cells with D4D6, with a specificity of 42.4%. For a threshold of ≥50% cells with SP384, only 18.5% of MAPK-negative cases would proceed to FISH, with a specificity of 31.4%. Based on our data we suggest an algorithm for screening for ROS1 rearrangements in NSCLC in which ROS1 FISH is only performed in cases that have been demonstrated to lack activating mutations in any MAPK pathway gene by comprehensive sequencing and ALK IHC, and show staining at any intensity in ≥50% of cells with clone SP384, or >0% cells with D4D6.

Histologic and Molecular Characterization of Non-Small Cell Lung Carcinoma With Discordant ROS1 Immunohistochemistry and Fluorescence In Situ Hybridization

INTRODUCTION

ROS1 immunohistochemical (IHC) positivity requires follow-up with confirmatory testing such as fluorescence in situ hybridization (FISH). Identifying predictive characteristics of false positive ROS1 IHC cases could aid in optimizing testing algorithms, decrease testing costs and preserve tissue.

MATERIALS AND METHODS

Retrospective results were retrieved for 2054 patients with non-small cell lung carcinoma submitted to our laboratory for molecular testing. Reflex ROS1 FISH was done on all ROS1 immunoreactive cases using ROS1 D4D6 antibody. Staining intensity and histo-score was recorded for all ROS1 immunoreactive cases. Results of any additional molecular testing (KRAS, BRAF, EGFR, ALK FISH, RET FISH, MET FISH) were also tabulated.

RESULTS

ROS1 immunoreactivity was seen in 305/2054 (14.8%) cases. Immunoreactivity was weak in majority of the cases with only 4.6% cases having an histo-score >100 and 5.9% of cases had moderate staining intensity. FISH was negative in 99% (302/305) cases with any degree of IHC expression (discordant cases) while 3 cases were positive by FISH. Diffuse strong IHC staining in greater than 90% of the tumor was noted in 6 cases, 3 (0.98%) of which were confirmed to have ROS1 rearrangement by FISH. The discordant cases had significantly higher rates of EGFR mutations (P<0.0005) in comparison to ROS1 IHC negative cases, were seen more often in adenocarcinoma and adenosquamous cell carcinoma (P<0.0005) with lepidic and acinar patterns, and more likely to occur in primary lung carcinomas (P<0.0005).

CONCLUSIONS

False positive ROS1 immunoreactivity was very frequent, occurred more commonly in primary NSCLC cases with acinar and/or lepidic histologies and was more likely in EGFR mutated cases. Using higher positivity thresholds for ROS1 IHC and incorporating the histologic and molecular correlates into algorithmic strategies could result in increased specificity and clinical utility of ROS1 IHC assay.

Canadian ROS proto-oncogene 1 study (CROS) for multi-institutional implementation of ROS1 testing in non-small cell lung cancer

Patients with non-small cell lung cancer (NSCLC) harboring ROS proto-oncogene 1 (ROS1) gene rearrangements show dramatic response to the tyrosine kinase inhibitor (TKI) crizotinib. Current best practice guidelines recommend that all advanced stage non-squamous NSCLC patients be also tested for ROS1 gene rearrangements. Several studies have suggested that ROS1 immunohistochemistry (IHC) using the D4D6 antibody may be used to screen for ROS1 fusion positive lung cancers, with assays showing high sensitivity but moderate to high specificity. A break apart fluorescence in situ hybridization (FISH) test is then used to confirm the presence of ROS1 gene rearrangement. The goal of Canadian ROS1 (CROS) study was to harmonize ROS1 laboratory developed testing (LDT) by using IHC and FISH assays to detect ROS1 rearranged lung cancers across Canadian pathology laboratories. Cell lines expressing different levels of ROS1 (high, low, none) were used to calibrate IHC protocols after which participating laboratories ran the calibrated protocols on a reference set of 24 NSCLC cases (9 ROS1 rearranged tumors and 15 ROS1 non-rearranged tumors as determined by FISH). Results were compared using a centralized readout. The stained slides were evaluated for the cellular localization of staining, intensity of staining, the presence of staining in non-tumor cells, the presence of non-specific staining (e.g. necrosis, extracellular mater, other) and the percent positive cells. H-score was also determined for each tumor. Analytical sensitivity and specificity harmonization was achieved by using low limit of detection (LOD) as either any positivity in the U118 cell line or H-score of 200 with the HCC78 cell line. An overall diagnostic sensitivity and specificity of up to 100% and 99% respectively was achieved for ROS1 IHC testing (relative to FISH) using an adjusted H-score readout on the reference cases. This study confirms that LDT ROS1 IHC assays can be highly sensitive and specific for detection of ROS1 rearrangements in NSCLC. As NSCLC can demonstrate ROS1 IHC positivity in FISH-negative cases, the degree of the specificity of the IHC assay, especially in highly sensitive protocols, is mostly dependent on the readout cut-off threshold. As ROS1 IHC is a screening assay for a rare rearrangements in NSCLC, we recommend adjustment of the readout threshold in order to balance specificity, rather than decreasing the overall analytical and diagnostic sensitivity of the protocols.

Validation of ROS1 by immunohistochemistry against fluorescent in situ hybridisation on cytology and small biopsy samples in a large teaching hospital

OBJECTIVE

Rearranged ROS1, present in 1%-2% of non-small cell lung cancer (NSCLC) patients, usually young, never or light smokers, is assessed by fluorescence in situ hybridization (FISH) to determine eligibility for tyrosine kinase inhibitors (TKI). Immunohistochemistry (IHC) for the protein product of ROS1 rearrangement, a cost-effective alternative, is validated on cytology and small biopsy samples.

METHODS

From 1 March to 31 December 2019, cytology cell blocks and small biopsy samples from a selected cohort of NSCLC patients were concurrently tested for ROS1 gene rearrangement by Vysis 6q22 Break Apart FISH probe and IHC using Cell Signalling D4D6 antibody. Mismatch cases were tested by an RNA fusion next generation sequencing (NGS) panel.

RESULTS

In a prospective population of 95 cases, 91 were negative and two were positive by both FISH and IHC. Both dual positive cases were female never smokers and benefited from TKI treatment. Another two cases were positive by FISH but negative by IHC and repeat by NGS showed one to be negative but one failed. Turnaround time for IHC was 0 to 8 days from request to authorisation, whilst that of FISH was 9 to 42 days at a cost of £51 and £159 respectively.

CONCLUSION

IHC to assess for the protein product of ROS1 gene rearrangement on cytology cell blocks and small biopsy samples in a routine setting is a promising screening method to assess eligibility for TKI treatment with positive and indeterminate cases confirmed by FISH or NGS as it has good negative predictive value, faster turnaround time and is cost effective, with proven technical and clinical validation.

Screening for ROS1 fusions in patients with advanced non-small cell lung carcinomas using the VENTANA ROS1 (SP384) Rabbit Monoclonal Primary Antibody

Introduction: The development of several ROS1 inhibitors means that the importance of accurately identifying ROS1-positive lung cancer patients has never been greater. Therefore, it is crucial that ROS1 testing assays become more standardized.Areas covered: Based on primary literature, combined with personal diagnostic and research experience, this review provide a pragmatic update on the use of the recently released VENTANA ROS1 (SP384) Rabbit Monoclonal Primary Antibody.Expert opinion: This assay provides high sensitivity, so it is an excellent analytical option when screening for ROS1 fusions in patients with advanced non-small cell lung carcinomas.

FISH patterns of ROS1, MET, and ALK with a correlation of ALK immunohistochemistry in lung cancer: a case for introducing ALK immunohistochemistry 'Equivocal' interpretation category in the Ventana anti-ALK (D5F3) CDx assay - A tertiary cancer center experience

Background

Mutations in ROS1, ALK, and MET genes are targetable alterations in non-small cell lung cancer (NSCLC). They can be evaluated by different techniques, most commonly fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC).

Methods

We explored the prevalence of ROS1, ALK, MET mutations, discuss clinicopathological associations and FISH signal patterns on 413 consecutive cases of EGFR negative lung carcinoma from March 2016 to April 2017 using FISH for ALK, ROS1, and MET along with ALK (D5F3) IHC.

Results

ROS1 gene rearrangement, ALK positivity (IHC and/or FISH), and MET amplification were seen in 18/358 (5%) cases, 76/392 cases (19.4%), and 10/370 (2.7%) cases, respectively. ALK FISH and ALK IHC were positive in 51/300 (17%) and 58/330 cases (17.57%), respectively, while 8/330 (2.4%) cases were ALK IHC "equivocal" of which 3/8 (37.5%) were ALK FISH positive. Of ALK FISH and IHC co-tested cases, 43/238 (18.07%) cases were positive by both techniques, while 15/43 (34.88%) of ALK positive cases showed discordant ALK FISH and IHC results. All ROS1 rearranged and MET amplified cases were adenocarcinoma. Signet ring cell histology was associated with 78.57% likelihood of being either ALK or ROS1 positive. Genomic heterogeneity was seen in 30% of MET amplified cases.

Conclusions

ALK/ROS1/MET gene alterations were found in 25.18% of NSCLC cases. An ALK IHC "equivocal" interpretation category should be incorporated into practice. Atypical patterns of ROS1 and genomic heterogeneity need to be evaluated further for any clinical relevance.

The Road Less Traveled: A Guide to Metastatic ROS1-Rearranged Non-Small-Cell Lung Cancer

Over the past decade, significant advances have been achieved in the diagnostic testing, treatment, and prognosis of advanced non-small-cell lung cancer (NSCLC). One of the most significant developments was the identification of specific gene alterations that define subsets of NSCLC. In 2007, ROS1 rearrangements were first described and observed in approximately 1%-2% of patients with NSCLC. Currently, crizotinib remains the therapy of choice for advanced ROS1-rearranged NSCLC without CNS metastases, while entrectinib has emerged as the preferred option for those with CNS metastases. The next-generation inhibitors under development are more potent, have better CNS efficacy, and can overcome important resistance mutations. In this review, we focus on the management of patients with advanced NSCLC harboring a ROS1 rearrangement. We aim to provide insight into the diagnosis, treatment approach, and emerging treatments in this subgroup of NSCLC.

Focus on ROS1-Positive Non-Small Cell Lung Cancer (NSCLC): Crizotinib, Resistance Mechanisms and the Newer Generation of Targeted Therapies

Simple Summary

Genetic rearrangements of the ROS1 gene account for up to 2% of NSCLC patients who sometimes develop brain metastasis, resulting in poor prognosis. This review discusses the tyrosine kinase inhibitor crizotinib plus updates and preliminary results with the newer generation of tyrosine kinase inhibitors, which have been specifically conceived to overcome crizotinib resistance, including brigatinib, cabozantinib, ceritinib, entrectinib, lorlatinib and repotrectinib. After introducing each agent’s properties, we provide suggestions on the best approaches to identify resistance mechanisms at an early stage, and we speculate on the most appropriate second-line therapies for patients who reported disease progression following crizotinib administration.

Abstract

The treatment of patients affected by non-small cell lung cancer (NSCLC) has been revolutionised by the discovery of druggable mutations. ROS1 (c-ros oncogene) is one gene with druggable mutations in NSCLC. ROS1 is currently targeted by several specific tyrosine kinase inhibitors (TKIs), but only two of these, crizotinib and entrectinib, have received Food and Drug Administration (FDA) approval. Crizotinib is a low molecular weight, orally available TKI that inhibits ROS1, MET and ALK and is considered the gold standard first-line treatment with demonstrated significant activity for lung cancers harbouring ROS1 gene rearrangements. However, crizotinib resistance often occurs, making the treatment of ROS1-positive lung cancers more challenging. A great effort has been undertaken to identify a new generation or ROS1 inhibitors. In this review, we briefly introduce the biology and role of ROS1 in lung cancer and discuss the underlying acquired mechanisms of resistance to crizotinib and the promising new agents able to overcome resistance mechanisms and offer alternative efficient therapies.

High prevalence of ROS1 gene rearrangement detected by FISH in EGFR and ALK negative lung adenocarcinoma

ROS1 rearrangement has become an important biomarker for targeted therapy in advanced lung adenocarcinoma (LUAD). The study aimed to evaluate the prevalence of ROS1 rearrangement in Chinese LUAD with EGFR wild-type and ALK fusion-negative status, and analyze the relationship with their clinicopathological characteristics. A large cohort of 589 patients of LUAD with EGFR/ALK wild-type, diagnosed between April 2014 and June 2018, was retrospectively analyzed. ROS1 rearrangement in all these cases was detected by FISH, and 8 selected cases with different positive and negative signals were confirmed by NGS. As a result, total of 56 cases with ROS1 rearrangements out of 589 LUADs (9.51%) were identified by FISH. The frequency of ROS1 rearrangement in women was 22.15% (35/158), which was statistically higher than 4.87% (21/431) in men (P < 0.001). The ROS1 positive rate in the patients with age < 50 years old (25.29%, 22/87) was statistically higher than that in the patients with age ≥ 50 (6.77%, 34/502) (P < 0.001). There was a trend that the frequency of ROS1 rearrangement in LUAD with stage III-IV was higher than that in stage I-II (9.56%, 39/408 vs 2.50%, 1/40), although it did not reach significant difference (P = 0.135). 37 out of 56 cases of ROS1 rearranged LUAD showed solid (n = 20, 35.71%) and invasive mucinous adenocarcinoma (n = 17, 30.36%) pathological subtypes. The median OS for patients of ROS1 rearranged LUAD treated with TKIs (n = 29) was 49.69 months (95% CI: 36.71, 62.67), compared with 32.55 months (95% CI: 23.24, 41.86) for those who did not receive TKI treatment (n = 16) (P = 0.040). The NGS results on ROS1 rearrangement in all the 8 cases were concordant with FISH results. In conclusion, high prevalence of ROS1 rearrangements occurs in EGFR/ALK wild-type LUAD detected by FISH, especially in younger, female, late stage patients, and in histological subtypes of solid and invasive mucinous adenocarcinoma.

Evaluation of a new diagnostic immunohistochemistry approach for ROS1 rearrangement in non-small cell lung cancer

BACKGROUND

ROS1 rearrangement is an oncogenic driver of non-small cell lung cancer (NSCLC). Accurate detection of ROS1 rearrangements in clinical tumor samples is vital. In this study, a new immunohistochemistry (IHC) monoclonal antibody (mAb) 1A1 assay was evaluated in patients with NSCLC.

METHODS

A cohort (cohort A) of 22 positive ROS1 reverse transcription-polymerase chain reaction (RT-PCR) samples were studied to evaluate the IHC-1A1 assay by comparing IHC-D4D6 mAb and another cohort (cohort B) of 178 consecutive cases to verify the assay by comparison using the RT-PCR method. IHC results with 2+ (H-score > 100) or 3+ staining was considered ROS1-positive.

RESULTS

In cohort A, ROS1 protein expression was evaluated in 22 samples by IHC-D4D6 and IHC-1A1 assays. For IHC-1A1, one patient was 1+ and 11 patients were 1+ for IHC-D4D6. ROS1 2-3+ was found in 36.4 % (8/22) of samples with IHC-D4D6 and 90.9 % (20/22) with IHC-1A1.The mean H-score of the 1A1 ROS1 2-3+ cases was 203.5. With the D4D6 clone, the mean H-score of the D4D6 ROS1 2∼3+ cases was 182.5. In the 178 NSCLC patients in cohort B, ROS1 rearrangement was detected with IHC and RT-PCR assays. Two patients had tumors with ROS1 IHC-1A1 3+ and one patient was IHC-1A1 2+. Among the three patients, two were confirmed to have ROS1 rearrangement by RT-PCR. None of the 175 ROS1 IHC-1A1 0-1+ samples were ROS1-positive by RT-PCR.

CONCLUSIONS

The results showed that the new IHC-1A1 ROS1 clone is a sensitive preliminary method and may be another excellent screening method in addition to the original IHC detection method to detect ROS1 gene rearrangements.

Translating Systems Medicine Into Clinical Practice: Examples From Pulmonary Medicine With Genetic Disorders, Infections, Inflammations, Cancer Genesis, and Treatment Implication of Molecular Alterations in Non-small-cell Lung Cancers and Personalized Medicine

Non-small-cell lung cancers (NSCLC) represent 85% of all lung cancers, with adenocarcinoma as the most common subtype. Since the 2000's, the discovery of molecular alterations including epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) rearrangements together with the development of specific tyrosine kinase inhibitors (TKIs) has facilitated the development of personalized medicine in the management of this disease. This review focuses on the biology of molecular alterations in NSCLC as well as the diagnostic tools and therapeutic alternatives available for each targetable alteration. Rapid and sensitive methods are essential to detect gene alterations, using tumor tissue biopsies or liquid biopsies. Massive parallel sequencing or Next Generation Sequencing (NGS) allows to simultaneously analyze numerous genes from relatively low amounts of DNA. The detection of oncogenic fusions can be conducted using fluorescence in situ hybridization, reverse-transcription polymerase chain reaction, immunohistochemistry, or NGS. EGFR mutations, ALK and ROS1 rearrangements, MET (MET proto-oncogenereceptor tyrosine kinase), BRAF (B-Raf proto-oncogen serine/threonine kinase), NTRK (neurotrophic tropomyosin receptor kinase), and RET (ret proto-oncogene) alterations are described with their respective TKIs, either already authorized or still in development. We have herein paid particular attention to the mechanisms of resistance to EGFR and ALK-TKI. As a wealth of diagnostic tools and personalized treatments are currently under development, a close collaboration between molecular biologists, pathologists, and oncologists is crucial.

Australian consensus statement for best practice ROS1 testing in advanced non-small cell lung cancer

Lung cancer is the most commonly diagnosed malignancy and the leading cause of death from cancer globally. Diagnosis of advanced non-small cell lung cancer (NSCLC) is associated with 5-year relative survival of 3.2%. ROS proto-oncogene 1 (ROS1) is an oncogenic driver of NSCLC occurring in up to 2% of cases and commonly associated with younger age and a history of never or light smoking. Results of an early trial with the tyrosine kinase inhibitor (TKI) crizotinib that inhibits tumours that harbour ROS1 rearrangements have shown an objective response rate (ORR) of 72% (95% CI 58-83%), median progression free survival (PFS) of 19.3 months (95% CI 15.2-39.1 months) and median overall survival (OS) of 51.4 months (95% CI 29.3 months to not reached). Therefore, with the availability of highly effective ROS1-targeted TKI therapy, upfront molecular testing for ROS1 status alongside EGFR and ALK testing is recommended for all patients with NSCLC. We review the tissue requirements for ROS1 testing by immunohistochemistry (IHC) and fluorescent in situ hybridisation (FISH) and we present a testing algorithm for advanced NSCLC and consider how the future of pathology testing for ROS1 may evolve.

Correlation of ROS1 Immunohistochemistry With ROS1 Fusion Status Determined by Fluorescence In Situ Hybridization

CONTEXT.—

The ability to determine ROS1 status has become mandatory for patients with lung adenocarcinoma, as many global authorities have approved crizotinib for patients with ROS1-positive lung adenocarcinoma.

OBJECTIVE.—

To present analytical correlation of the VENTANA ROS1 (SP384) Rabbit Monoclonal Primary Antibody (ROS1 [SP384] antibody) with ROS1 fluorescence in situ hybridization (FISH).

DESIGN.—

The immunohistochemistry (IHC) and FISH analytical comparison was assessed by using 122 non-small cell lung cancer samples that had both FISH (46 positive and 76 negative cases) and IHC staining results available. In addition, reverse transcription-polymerase chain reaction (RT-PCR) as well as DNA and RNA next-generation sequencing (NGS) were used to further examine the ROS1 status in cases that were discrepant between FISH and IHC, based on staining in the cytoplasm of 2+ or above in more than 30% of total tumor cells considered as IHC positive. Here, we define the consensus status as the most frequent result across the 5 different methods (IHC, FISH, RT-PCR, RNA NGS, and DNA NGS) we used to determine ROS1 status in these cases.

RESULTS.—

Of the IHC scoring methods examined, staining in the cytoplasm of 2+ or above in more than 30% of total tumor cells considered as IHC positive had the highest correlation with a FISH-positive status, reaching a positive percentage agreement of 97.8% and negative percentage agreement of 89.5%. A positive percentage agreement (100%) and negative percentage agreement (92.0%) was reached by comparing ROS1 (SP384) using a cutoff for staining in the cytoplasm of 2+ or above in more than 30% of total tumor cells to the consensus status.

CONCLUSIONS.—

Herein, we present a standardized staining protocol for ROS1 (SP384) and data that support the high correlation between ROS1 status and ROS1 (SP384) antibody.

Fluorescence in Situ Hybridization (FISH) for Detecting Anaplastic Lymphoma Kinase (ALK) Rearrangement in Lung Cancer: Clinically Relevant Technical Aspects

In 2011, the Vysis Break Apart ALK fluorescence in situ hybridization (FISH) assay was approved by the United States Food and Drug Administration as a companion diagnostic for detecting ALK rearrangement in lung cancer patients who may benefit from treatment of tyrosine kinase inhibitor therapy. This assay is the current “gold standard”. According to updated ALK testing guidelines from the College of American Pathologists, the International Association for the Study of Lung Cancer and the Association for Molecular Pathology published in 2018, ALK immunohistochemistry is formally an alternative to ALK FISH, and simultaneous detection of multiple hot spots, including, at least, ALK, ROS1, RET, MET, ERBB2, BRAF and KRAS genes is also recommended while performing next generation sequencing (NGS)-based testing. Therefore, ALK status in a specimen can be tested by different methods and platforms, even in the same institution or laboratory. In this review, we discuss several clinically relevant technical aspects of ALK FISH, including pros and cons of the unique two-step (50- to 100-cell) analysis approach employed in the Vysis Break Apart ALK FISH assay, including: the preset cutoff value of ≥15% for a positive result; technical aspects and biology of discordant results obtained by different methods; and incidental findings, such as ALK copy number gain or amplification and co-existent driver mutations. These issues have practical implications for ALK testing in the clinical laboratory following the updated guidelines.

Assessment of a New ROS1 Immunohistochemistry Clone (SP384) for the Identification of ROS1 Rearrangements in Patients with Non-Small Cell Lung Carcinoma: the ROSING Study

INTRODUCTION

The ROS1 gene rearrangement has become an important biomarker in NSCLC. The College of American Pathologists/International Association for the Study of Lung Cancer/Association for Molecular Pathology testing guidelines support the use of ROS1 immunohistochemistry (IHC) as a screening test, followed by confirmation with fluorescence in situ hybridization (FISH) or a molecular test in all positive results. We have evaluated a novel anti-ROS1 IHC antibody (SP384) in a large multicenter series to obtain real-world data.

METHODS

A total of 43 ROS1 FISH-positive and 193 ROS1 FISH-negative NSCLC samples were studied. All specimens were screened by using two antibodies (clone D4D6 from Cell Signaling Technology and clone SP384 from Ventana Medical Systems), and the different interpretation criteria were compared with break-apart FISH (Vysis). FISH-positive samples were also analyzed with next-generation sequencing (Oncomine Dx Target Test Panel, Thermo Fisher Scientific).

RESULTS

An H-score of 150 or higher or the presence of at least 70% of tumor cells with an intensity of staining of 2+ or higher by the SP384 clone was the optimal cutoff value (both with 93% sensitivity and 100% specificity). The D4D6 clone showed similar results, with an H-score of at least 100 (91% sensitivity and 100% specificity). ROS1 expression in normal lung was more frequent with use of the SP384 clone (p < 0.0001). The ezrin gene (EZR)-ROS1 variant was associated with membranous staining and an isolated green signal FISH pattern (p = 0.001 and p = 0.017, respectively).

CONCLUSIONS

The new SP384 ROS1 IHC clone showed excellent sensitivity without compromising specificity, so it is another excellent analytical option for the proposed testing algorithm.

Immunocytochemistry for predictive biomarker testing in lung cancer cytology

With an escalating number of predictive biomarkers emerging in non-small cell lung carcinoma (NSCLC), immunohistochemistry (IHC) is being used as a rapid and cost-effective tool for the screening and detection of many of these markers. In particular, robust IHC assays performed on formalin-fixed, paraffin-embedded (FFPE) tumor tissue are widely used as surrogate markers for ALK and ROS1 rearrangements and for detecting programmed death ligand 1 (PD-L1) expression in patients with advanced NSCLC; in addition, they have become essential for treatment decisions. Cytology samples represent the only source of tumor in a significant proportion of patients with inoperable NSCLC, and there is increasing demand for predictive biomarker testing on them. However, the wide variation in the types of cytology samples and their preparatory methods, the use of alcohol-based fixatives that interfere with immunochemistry results, the difficulty in procurement of cytology-specific controls, and the uncertainty regarding test validity have resulted in underutilization of cytology material for predictive immunocytochemistry (ICC), and most cytopathologists limit such testing to FFPE cell blocks (CBs). The purpose of this review is to: 1) analyze various preanalytical, analytical, and postanalytical factors influencing ICC results; 2) discuss measures for validation of ICC protocols; and 3) summarize published data on predictive ICC for ALK, ROS1, EGFR gene alterations and PD-L1 expression on lung cancer cytology. Based on our experience and from a review of the literature, we conclude that cytology specimens are in principal suitable for predictive ICC, but proper optimization and rigorous quality control for high-quality staining are essential, particularly for non-CB preparations.

Multicenter Evaluation of a Novel ROS1 Immunohistochemistry Assay (SP384) for Detection of ROS1 Rearrangements in a Large Cohort of Lung Adenocarcinoma Patients

INTRODUCTION

The detection of a ROS1 rearrangement in advanced and metastatic lung adenocarcinoma (LUAD) led to a targeted treatment with tyrosine kinase inhibitors with favorable progression-free survival and overall survival of the patients. Thus, it is mandatory to screen for the ROS1 rearrangement in all these patients. ROS1 rearrangements can be detected using break-apart fluorescence in situ hybridization (FISH), which is the gold standard; however, ROS1 immunohistochemistry (IHC) can be used as a screening test because it is widely available, easy and rapid to perform, and cost-effective.

METHODS

We evaluated the diagnostic accuracy and interpathologist agreement of two anti-ROS1 IHC clones, SP384 (Ventana, Tucson, Arizona) and D4D6 (Cell Signaling, Danvers, Massachusetts), in a training cohort of 51 positive ROS1 FISH LUAD cases, and then in a large validation cohort of 714 consecutive cases of LUAD from six routine molecular pathology platforms.

RESULTS

In the two cohorts, the SP384 and D4D6 clones show variable sensitivity and specificity rates on the basis of two cutoff points greater than or equal to 1+ (all % tumor cells) and greater than or equal to 2+ (>30% stained tumor cells). In the validation cohort, the D4D6 yielded the best accuracy for the presence of a ROS1 rearrangement by FISH. Interpathologist agreement was moderate to good (interclass correlation 0.722-0.874) for the D4D6 clone and good to excellent (interclass correlation: 0.830-0.956) for the SP384 clone.

CONCLUSIONS

ROS1 IHC is an effective screening tool for the presence of ROS1 rearrangements. However, users must be acutely aware of the variable diagnostic performance of different anti-ROS1 antibodies before implementation into routine clinical practice.

Clinicopathological features and clinical efficacy of crizotinib in Chinese patients with ROS1-positive non-small cell lung cancer

C-ros oncogene 1 receptor tyrosine kinase (ROS1) rearrangement forms a novel molecular subgroup of non-small cell lung cancer (NSCLC). The present study explored the clinicopathological features and clinical efficacy of crizotinib in patients with ROS1-positive NSCLC. A retrospective analysis of 2,617 cases of NSCLC diagnosed between January 2013 and December 2016 was performed. ROS1 fusion genes were detected by reverse transcription-quantitative polymerase chain reaction, fluorescence in situ hybridization or next-generation sequencing techniques, and patients positive for the ROS1 fusion gene received oral treatment with crizotinib. The ROS1 fusion was identified in 67 out of 2,617 cases (2.56%), including 21 cases that were male and 46 cases that were female. The median age was 68 years. Among these cases, 59 (88.06%) were adenocarcinoma and 8 were non-adenocarcinoma. According to Tumor-Node-Metastasis (TNM) staging, 4 cases were stage I-IIIa and 63 (94.02%) were stage IIIb-IV. The epidermal growth factor receptor (EGFR) gene status included 60 cases of wild-type, 1 case of co-mutation and 6 unknown cases. Statistically significant differences were identified for sex, TNM staging and EGFR gene status between ROS1 fusion gene-positive and -negative patients (P<0.001). A total of 23 patients received oral treatment with crizotinib, of which 13 (56.52%), 5 (21.74%) and 5 (21.74%) patients demonstrated a partial response, stable disease and progressive disease, respectively. The objective response rate was 56.52% and the disease control rate was 78.26%. Among all patients, the median progression-free survival (mPFS) time was 14.5 months. No differences were revealed in the mPFS time with regard to age, sex, smoking history, performance status score, histopathological type, TNM staging, tumor protein p53 gene status, EGFR gene status and first-line crizotinib treatment, whether by single or multiple factor analysis. The grade 3/4 treatment-associated adverse events included gastrointestinal disturbance, followed by increased transaminase concentration. In conclusion, the rate of ROS1 fusion in NSCLC among the patients is low, and crizotinib is an effective and safe drug for the treatment of ROS1-positive advanced NSCLC.

Prevalence of ROS1 fusion in Chinese patients with non-small cell lung cancer

BACKGROUND

The study was conducted to investigate the clinicopathological features and prevalence of ROS1 gene fusion in Chinese patients with non-small cell lung cancer (NSCLC).

METHODS

The presence of ROS1 fusion was assessed by quantitative real-time PCR. Associations between ROS1 fusion and clinical characteristics were analyzed.

RESULTS

In total, 6066 patients with pathologically confirmed NSCLC and ROS1 fusion test results were enrolled. The average age was 60.89 ± 10.60 years and fusion was detected in 157 (2.59%) patients. Fusion frequency was significantly correlated with age, gender, smoking status (all P < 0.001), pathology type (P = 0.017), and lymph node metastasis stage (P = 0.027). ROS1 fusion-positive patients were significantly younger (55.68 ± 11.34 vs. negative 61.02 ± 10.44 years; P < 0.01). Fusion frequency was higher in women (3.71% vs. men 1.81%), never-smokers (3.33% vs. smokers 1.21%), and patients with adenocarcinoma (2.77% vs. squamous lung cancer 0.93%) and at advanced node stages (1.31%, 1.40%, 2.07%, and 3.23% for N0, N1, N2, and N3, respectively). No significant correlation between ROS1 fusion status and pathological stage was found in subgroups classified by pathological, tumor, or metastasis stage (P > 0.05). Age, smoking status, and lymph node stage were statistically significantly correlated with ROS1 fusion frequency (all P < 0.05); gender and pathology type were not significantly correlated with ROS1 fusion status after adjusting for smoking status.

CONCLUSION

An overall ROS1 fusion frequency of 2.59% was confirmed in this study. ROS1 fusion was more prevalent among younger patients, never-smokers, and those at advanced node stages.

PD-L1 expression in ROS1-rearranged non-small cell lung cancer: A study using simultaneous genotypic screening of EGFR, ALK, and ROS1

Background

The aim of the current study was to investigate the prevalence and clinicopathologic characteristics of ROS1‐rearranged non‐small cell lung cancer (NSCLC) in routine genotypic screening in conjunction with the study of PD‐L1 expression, a biomarker for first‐line treatment decisions.

Methods

Reflex simultaneous genotypic screening for EGFR by peptide nucleic acid clamping, and ALK and ROS1 by fluorescence in situ hybridization (FISH) was performed on consecutive NSCLC cases at the time of initial pathologic diagnosis. We evaluated genetic aberrations, clinicopathologic characteristics, and PD‐L1 tumor proportion score (TPS) using a PD‐L1 22C3 assay kit.

Results

In 407 consecutive NSCLC patients, simultaneous genotyping identified 14 (3.4%) ROS1 and 19 (4.7%) ALK rearrangements, as well as 106 (26%) EGFR mutations. These mutations were mutually exclusive and were found in patients with similar clinical features, including younger age, a prevalence in women, adenocarcinoma, and advanced stage. The PD‐L1 assay was performed on 130 consecutive NSCLC samples. High PD‐L1 expression (TPS ≥ 50%) was observed in 29 (22.3%) tumors. PD‐L1 expression (TPS ≥ 1%) was significantly associated with wild type EGFR, while ROS1 rearrangement was associated with high PD‐L1 expression. Of the 14 cases with ROS1 rearrangement, 12 (85.7%) showed PD‐L1 expression and 5 (35.7%) showed high PD‐L1 expression.

Conclusion

In the largest consecutive routine Asian NSCLC cohort analyzed to date, we found that high PD‐L1 expression frequently overlapped with ROS1 rearrangement, while it negatively correlated with EGFR mutations.

Diagnostic and Predictive Immunohistochemistry for Non-Small Cell Lung Carcinomas

Non-small cell lung carcinoma (NSCLC) accounts for significant morbidity and mortality worldwide, with most patients diagnosed at advanced stages and managed increasingly with targeted therapies and immunotherapy. In this review, we discuss diagnostic and predictive immunohistochemical markers in NSCLC, one of the most common tumors encountered in surgical pathology. We highlight 2 emerging diagnostic markers: nuclear protein in testis (NUT) for NUT carcinoma; SMARCA4 for SMARCA4-deficient thoracic tumors. Given their highly aggressive behavior, proper recognition facilitates optimal management. For patients with advanced NSCLCs, we discuss the utility and limitations of immunohistochemistry (IHC) for the "must-test" predictive biomarkers: anaplastic lymphoma kinase, ROS1, programmed cell death protein 1, and epidermal growth factor receptor. IHC using mutant-specific BRAF V600E, RET, pan-TRK, and LKB1 antibodies can be orthogonal tools for screening or confirmation of molecular events. ERBB2 and MET alterations include both activating mutations and gene amplifications, detection of which relies on molecular methods with a minimal role for IHC in NSCLC. IHC sits at the intersection of an integrated surgical pathology and molecular diagnostic practice, serves as a powerful functional surrogate for molecular testing, and is an indispensable tool of precision medicine in the care of lung cancer patients.

Lung adenocarcinoma with concurrent ALK and ROS1 rearrangement: A case report and review of the literatures

ALK and ROS1 are prognostic and predictive tumor markers in non-small cell lung carcinoma (NSCLC), which are more often found in lung adenocarcinomas as with other oncogenes such as EGFR, KRAS, or C-MET. Their positivity is 2.6% and 1.3%, respectively, and patients who have mutations in both genes are extremely rare. Here, we report a 61-year-old male diagnosed with acinar adenocarcinoma, who was shown to have both ALK and ROS1 rearrangements but was EGFR- and C-MET mutation-negative. He was treated surgically and received targeted therapy. Our review of the literature revealed that few such cases of concurrent ALK and ROS1 rearrangements have been reported. This information furthers our understanding of the molecular biology underlying NSCLC which will aid the selection of optimal treatment for patients with more than one driver mutation.

c-MET Overexpression as a Poor Predictor of MET Amplifications or Exon 14 Mutations in Lung Sarcomatoid Carcinomas

INTRODUCTION

MNNG HOS transforming gene (MET) abnormalities such as amplification and exon 14 mutations may be responsive to targeted therapies. They are prevalent in lung sarcomatoid carcinomas (LSCs) and must be diagnosed as efficiently as possible. Hypothetically, c-MET overexpression by immunohistochemistry (IHC) may prove effective as a screening test for MET abnormalities.

METHODS

Tissue samples were obtained from consecutive patients with a resected LSC in four oncologic centers. IHC was performed using the SP44 antibody (Ventana, Tucson, Arizona) and evaluated using the MetMab score and H-score. Fluorescence in situ hybridization was applied with the dual color probe set from Zytovision (Clinisciences, Nanterre, France). True MET amplification was diagnosed when MET gene copy number was 5 or greater and the ratio between MET gene copy number and chromosome 7 number was greater than 2. All MET exon 14 alterations including those affecting splice sites occurring within splice donor and acceptor sites were detected in the routine molecular testing on genetic platforms.

RESULTS

A total of 81 LSCs were included. Fourteen (17%) exhibited positive IHC using the MetMab score and 15 (18.5%) using the H-score. MET amplification was detected in six tumors (8.5%) and MET exon 14 mutation in five (6%). A weak positive correlation between IHC and fluorescence in situ hybridization was found (r = 0.27, p = 0.0001). IHC sensitivity for MET amplification was 50%, with a specificity of 83%, positive predictive value of 21.4%, and negative predictive value of 94.7%. IHC sensitivity for MET exon 14 mutations was 20%, with a specificity of 83%, positive predictive value of 7%, and negative predictive value of 94%.

CONCLUSION

IHC is not a relevant screening tool for MET abnormalities in LSC.

Clinicopathological significance and diagnostic approach of ROS1 rearrangement in non-small cell lung cancer: a meta-analysis: ROS1 in non-small cell lung cancer

PURPOSE

The aim of this study was to investigate the rate of ROS1 rearrangement and concordance between ROS1 immunohistochemistry (IHC) and molecular tests in non-small cell lung cancer (NSCLC).

METHODS

The study included 10,898 NSCLC cases from 21 eligible studies. ROS1 rearrangement rates were evaluated in NSCLC by a meta-analysis, including subgroup analyses. In addition, we performed a concordance analysis and a diagnostic test accuracy review of ROS1 IHC in NSCLC.

RESULTS

The estimated overall rate of ROS1 rearrangement and IHC positivity was 2.4% (95% confidence interval (CI) 1.5, 3.7). In the subgroup analysis, which was based on tumor subtype, the rate of ROS1 rearrangement and IHC positivity was 2.9% (95% CI 1.9, 4.5) and 0.6% (95% CI 0.3, 1.2) in adenocarcinoma and non-adenocarcinoma, respectively. The overall concordance rate between ROS1 IHC and molecular tests was 93.4% (95% CI 78.3, 98.2). In ROS1 IHC positive and negative cases, the concordance rates were 79.0% (95% CI 43.3, 94.9) and 97.0% (95% CI 83.3, 99.5), respectively. The pooled sensitivity and the specificity of ROS1 IHC were 0.90 (95% CI 0.70, 0.99) and 0.82 (95% CI 0.79, 0.84), respectively. The diagnostic odds ratio and the area under the curve of the summary receiver operating characteristic curve were 118.01 (95% CI 11.81, 1179.67) and 0.9417, respectively.

CONCLUSION

The rates of ROS1 rearrangement differed by tumor histologic subtype in NSCLC. ROS1 IHC may be useful for the detection of ROS1 rearrangement in NSCLC. Detailed criteria for evaluating ROS1 IHC are needed before it can be applied in daily practice.

A genomic and clinicopathological study of non-small-cell lung cancers with discordant ROS1 gene status by fluorescence in-situ hybridisation and immunohistochemical analysis

AIMS

ROS1 immunohistochemistry (IHC) using D4D6 antibody is a useful tool for screening patients with non-small-cell lung cancer (NSCLC) who may be suitable for targeted therapy. Many studies and our data have identified cases that express the ROS1 protein strongly but are negative for ROS1 by fluorescence in-situ hybridisation (FISH). The present study investigated the driver mutation and clinicopathological characteristics of 26 discordant cases (ROS1 IHC-positive but FISH-negative) to find new clues for distinguishing real ROS1-rearranged cases.

METHODS AND RESULTS

Tumours from 26 discordant cases were analysed for clinicopathological characteristics, mutations in EGFR, KRAS, ERBB2, BRAF and PIK3CA; fusions in ALK and RET; and amplifications in MET, ERBB2 and ROS1. ROS1-rearranged NSCLCs were significantly more likely to be found in younger patients and at an advanced stage; they showed cribriform features, extracellular mucus and psammoma bodies, whereas ROS1-discordant cases were found in older patients at a relatively early tumour-node-metastasis (TNM) stage and showed a lepidic growth pattern (all P < 0.001). Most ROS1-rearranged NSCLCs had no concurrent mutation, whereas 73% of discordant cases harboured genetic aberrations, including EGFR and ERBB2. Compared with general lung adenocarcinomas, ERBB-2 abnormality was disproportionately high in ROS1-discordant cases. Moreover, we optimised the scoring criteria for ROS1 IHC as 'H score > 150 and no concurrent mutations'; the specificity was then increased to 81.6%.

CONCLUSIONS

Compared with ROS1-rearranged cases, ROS1-discordant patients showed distinct clinical and morphological features and often harboured another oncogenic driver alteration. The use of optimised screening criteria will increase the specificity of ROS1 antibody.

A stitch in time saves nine: external quality assessment rounds demonstrate improved quality of biomarker analysis in lung cancer

Biomarker analysis has become routine practice in the treatment of non-small cell lung cancer (NSCLC). To ensure high quality testing, participation to external quality assessment (EQA) schemes is essential. This article provides a longitudinal overview of the EQA performance for EGFR, ALK, and ROS1 analyses in NSCLC between 2012 and 2015.

The four scheme years were organized by the European Society of Pathology according to the ISO 17043 standard. Participants were asked to analyze the provided tissue using their routine procedures.

Analysis scores improved for individual laboratories upon participation to more EQA schemes, except for ROS1 immunohistochemistry (IHC). For EGFR analysis, scheme error rates were 18.8%, 14.1% and 7.5% in 2013, 2014 and 2015 respectively. For ALK testing, error rates decreased between 2012 and 2015 by 5.2%, 3.2% and 11.8% for the fluorescence in situ hybridization (FISH), FISH digital, and IHC subschemes, respectively. In contrast, for ROS1 error rates increased between 2014 and 2015 for FISH and IHC by 3.2% and 9.3%. Technical failures decreased over the years for all three markers.

Results show that EQA contributes to an ameliorated performance for most predictive biomarkers in NSCLC. Room for improvement is still present, especially for ROS1 analysis.

Advanced lung adenocarcinomas with ROS1-rearrangement frequently show hepatoid cell

Defining distinctive histologic characteristics of ROS1-rearranged non-small-cell lung carcinomas (NSCLCs) may help identify cases that merit molecular testing. However, the majority of previous reports have focused on surgical specimens but only limited studies assessed histomorphology of advanced NSCLCs. In order to identify the clinical and histological characteristics of ROS1-rearranged advanced NSCLCs, we examined five hundred sixteen Chinese patients with advanced NSCLCs using ROS1 fluorescence in situ hybridization and real-time polymerase chain reaction and then analyzed for clinical and pathological features. We performed univariate and multivariate analyses to identify predictive factors associated with ROS1 rearrangement. 19 tumors were identified with ROS1 rearrangement (3.7% of adenocarcinomas). 16 ROS1+ and 122 ROS1- samples with available medical records and enough tumor cells were included for histological analysis. Compared with ROS1-negative advanced NSCLCs, ROS1-rearranged advanced NSCLCs were associated with a younger age at presentation. ROS1 rearrangements were not significantly associated with sex, smoking history, drinking history and metastatic sites. The most common histological pattern was solid growth (12/16), followed by acinar (4/16) growth. 66.7% cases with solid growth pattern showed hepatoid cytology (8/12) and 75% cases with acinar growth pattern showed a cribriform structure (3/4). 18.8% cases were found to have abundant extracellular mucus or signet-ring cells (3/16). Only one case with solid growth pattern showed psammomatous calcifications. In conclusion, age, hepatoid cytology and cribriform structure are the independent predictors for ROS1-rearranged advanced NSCLCs, recognizing these may be helpful in finding candidates for genomic alterations, especially when available tissue samples are limited.

Update on Immunohistochemistry for the Diagnosis of Lung Cancer

Immunohistochemistry is a widely available technique that is less challenging and can provide clinically meaningful results quickly and cost-efficiently in comparison with other techniques. In addition, immunohistochemistry allows for the evaluation of cellular localization of proteins in the context of tumor structure. In an era of precision medicine, pathologists are required to classify lung cancer into specific subtypes and assess biomarkers relevant to molecular-targeted therapies. This review summarizes the hot topics of immunohistochemistry in lung cancer, including (i) adenocarcinoma vs squamous cell carcinoma; (ii) neuroendocrine markers; (iii) ALK, ROS1, and EGFR; (iv) PD-L1 (CD274); (v) lung carcinoma vs malignant mesothelioma; and (vi) NUT carcinoma. Major pitfalls in evaluating immunohistochemical results are also described.

Updated Molecular Testing Guideline for the Selection of Lung Cancer Patients for Treatment With Targeted Tyrosine Kinase Inhibitors: Guideline From the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology

CONTEXT

- In 2013, an evidence-based guideline was published by the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology to set standards for the molecular analysis of lung cancers to guide treatment decisions with targeted inhibitors. New evidence has prompted an evaluation of additional laboratory technologies, targetable genes, patient populations, and tumor types for testing.

OBJECTIVE

- To systematically review and update the 2013 guideline to affirm its validity; to assess the evidence of new genetic discoveries, technologies, and therapies; and to issue an evidence-based update.

DESIGN

- The College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology convened an expert panel to develop an evidence-based guideline to help define the key questions and literature search terms, review abstracts and full articles, and draft recommendations.

RESULTS

- Eighteen new recommendations were drafted. The panel also updated 3 recommendations from the 2013 guideline.

CONCLUSIONS

- The 2013 guideline was largely reaffirmed with updated recommendations to allow testing of cytology samples, require improved assay sensitivity, and recommend against the use of immunohistochemistry for EGFR testing. Key new recommendations include ROS1 testing for all adenocarcinoma patients; the inclusion of additional genes ( ERBB2, MET, BRAF, KRAS, and RET) for laboratories that perform next-generation sequencing panels; immunohistochemistry as an alternative to fluorescence in situ hybridization for ALK and/or ROS1 testing; use of 5% sensitivity assays for EGFR T790M mutations in patients with secondary resistance to EGFR inhibitors; and the use of cell-free DNA to "rule in" targetable mutations when tissue is limited or hard to obtain.

Updated Molecular Testing Guideline for the Selection of Lung Cancer Patients for Treatment With Targeted Tyrosine Kinase Inhibitors: Guideline From the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology

CONTEXT

In 2013, an evidence-based guideline was published by the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology to set standards for the molecular analysis of lung cancers to guide treatment decisions with targeted inhibitors. New evidence has prompted an evaluation of additional laboratory technologies, targetable genes, patient populations, and tumor types for testing.

OBJECTIVE

To systematically review and update the 2013 guideline to affirm its validity; to assess the evidence of new genetic discoveries, technologies, and therapies; and to issue an evidence-based update.

DESIGN

The College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology convened an expert panel to develop an evidence-based guideline to help define the key questions and literature search terms, review abstracts and full articles, and draft recommendations.

RESULTS

Eighteen new recommendations were drafted. The panel also updated 3 recommendations from the 2013 guideline.

CONCLUSIONS

The 2013 guideline was largely reaffirmed with updated recommendations to allow testing of cytology samples, require improved assay sensitivity, and recommend against the use of immunohistochemistry for EGFR testing. Key new recommendations include ROS1 testing for all adenocarcinoma patients; the inclusion of additional genes (ERBB2, MET, BRAF, KRAS, and RET) for laboratories that perform next-generation sequencing panels; immunohistochemistry as an alternative to fluorescence in situ hybridization for ALK and/or ROS1 testing; use of 5% sensitivity assays for EGFR T790M mutations in patients with secondary resistance to EGFR inhibitors; and the use of cell-free DNA to "rule in" targetable mutations when tissue is limited or hard to obtain.

Updated Molecular Testing Guideline for the Selection of Lung Cancer Patients for Treatment With Targeted Tyrosine Kinase Inhibitors: Guideline From the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology

CONTEXT

In 2013, an evidence-based guideline was published by the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology to set standards for the molecular analysis of lung cancers to guide treatment decisions with targeted inhibitors. New evidence has prompted an evaluation of additional laboratory technologies, targetable genes, patient populations, and tumor types for testing.

OBJECTIVE

To systematically review and update the 2013 guideline to affirm its validity; to assess the evidence of new genetic discoveries, technologies, and therapies; and to issue an evidence-based update.

DESIGN

The College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology convened an expert panel to develop an evidence-based guideline to help define the key questions and literature search terms, review abstracts and full articles, and draft recommendations.

RESULTS

Eighteen new recommendations were drafted. The panel also updated 3 recommendations from the 2013 guideline.

CONCLUSIONS

The 2013 guideline was largely reaffirmed with updated recommendations to allow testing of cytology samples, require improved assay sensitivity, and recommend against the use of immunohistochemistry for EGFR testing. Key new recommendations include ROS1 testing for all adenocarcinoma patients; the inclusion of additional genes (ERBB2, MET, BRAF, KRAS, and RET) for laboratories that perform next-generation sequencing panels; immunohistochemistry as an alternative to fluorescence in situ hybridization for ALK and/or ROS1 testing; use of 5% sensitivity assays for EGFR T790M mutations in patients with secondary resistance to EGFR inhibitors; and the use of cell-free DNA to "rule in" targetable mutations when tissue is limited or hard to obtain.

ROS1 Gene Fusion in Advanced Lung Cancer in Women: A Systematic Analysis, Review of the Literature, and Diagnostic Algorithm

Purpose

Crizotinib, a mesenchymal-epithelial transition/anaplastic lymphoma kinase/c-ros oncogene 1 (ROS1) inhibitor, has recently been approved by the US Food and Drug Administration for the treatment of patients with advanced ROS1-positive non–small-cell lung cancer (NSCLC). Therefore, interest in ROS1 testing is growing. ROS1 gene fusions affect approximately 0.5% to 2% of unselected NSCLCs. Limited data are available on the prevalence and distribution of ROS1 fusions in patients with advanced-stage NSCLC.

Material and Methods

A series of 727 lung adenocarcinomas from patients with stage IV disease, negative for epidermal growth factor receptor and anaplastic lymphoma kinase alterations, were tested for ROS1 fusions by fluorescent in situ hybridization analysis, with confirmation by immunohistochemistry. Results were correlated with clinicopathologic parameters and compared with data from the literature.

Results

ROS1 fusions were detected in 29 patients (4%), including 27 of 266 females (10.2%) and two of 461 males (0.4%; P = 1.2E-10). The mean age of patients with ROS1-positive disease was lower than that of patients with ROS1-negative disease (49.21 v 62.96 years, respectively; P = 1.1E-10). Eleven of 583 smokers (1.9%) and 18 of 144 nonsmokers (12.5%) showed ROS1 rearrangement ( P = 4.05E-7). By logistic regression analysis, ROS1 fusions were independently associated with female sex, younger age at diagnosis, and absence of smoking history, (odds ratios, 12.4, 7.9, and 3.6, respectively). These data, integrated with those reported in the literature, indicate that the prevalence of ROS1 fusions in females and in nonsmokers was higher in patients with advanced disease than in patients with operable disease (11.2% v 3.1%, P < .001; 11.6% v 2.8%, P < .001, respectively). The mean age at diagnosis was significantly lower in patients with advanced disease (49.8 years) than in patients with operable disease (55.6 years; P < .001).

Conclusion

Our data indicate that ROS1 fusions in patients with advanced-stage lung adenocarcinoma are more frequent in females, particularly if young and nonsmokers. A diagnostic algorithm for an accurate screening of ROS1 alterations was elaborated.

Concurrent ROS1 gene rearrangement and KRAS mutation in lung adenocarcinoma: A case report and literature review

Lung adenocarcinomas with gene rearrangement in the receptor tyrosine kinase ROS1 have emerged as a rare molecular subtype. Although these lung adenocarcinomas respond to ROS1tyrosine kinase inhibitors, many patients ultimately acquire resistance. ROS1gene rearrangement is generally mutually exclusive with other driver genomic alterations, such as those in EGFR, KRAS, or ALK, thus multiple genomic alterations are extremely rare. Herein, we report a case of a 42-year-old man diagnosed with lung adenocarcinoma positive for a SDC4-ROS1 fusion, who was treated with crizotinib followed by three cycles of chemotherapy. A biopsy acquired after disease progression revealed the original SDC4-ROS1 fusion along with a KRAS point mutation (p.G12D).We reviewed the related literature to determine the frequency of gene mutations in non-small cell lung cancer patients. A better understanding of the molecular biology of non-small cell lung cancer with multiple driver genomic aberrations will assist in determining optimal treatment.

Immunohistochemistry for predictive biomarkers in non-small cell lung cancer

In the era of targeted therapy, predictive biomarker testing has become increasingly important for non-small cell lung cancer. Of multiple predictive biomarker testing methods, immunohistochemistry (IHC) is widely available and technically less challenging, can provide clinically meaningful results with a rapid turn-around-time and is more cost efficient than molecular platforms. In fact, several IHC assays for predictive biomarkers have already been implemented in routine pathology practice. In this review, we will discuss: (I) the details of anaplastic lymphoma kinase (ALK) and proto-oncogene tyrosine-protein kinase ROS (ROS1) IHC assays including the performance of multiple antibody clones, pros and cons of IHC platforms and various scoring systems to design an optimal algorithm for predictive biomarker testing; (II) issues associated with programmed death-ligand 1 (PD-L1) IHC assays; (III) appropriate pre-analytical tissue handling and selection of optimal tissue samples for predictive biomarker IHC.