Comparison of detection methods and follow-up study on the tyrosine kinase inhibitors therapy in non-small cell lung cancer patients with ROS1 fusion rearrangement

Rediscovering immunohistochemistry in lung cancer

Several observations indicate that protein expression analysis by immunohistochemistry (IHC) remains relevant in individuals with non-small-cell lung cancer (NSCLC) when considering targeted therapy, as an early step in diagnosis and for therapy selection. Since the advent of next-generation sequencing (NGS), the role of IHC in testing for NSCLC biomarkers has been forgotten or ignored. We discuss how protein-level investigations maintain a critical role in defining sensitivity to lung cancer therapies in oncogene- and non-oncogene-addicted cases and in patients eligible for immunotherapy, suggesting that IHC testing should be reconsidered in clinical practice. We also argue how a panel of IHC tests should be considered complementary to NGS and other genomic assays. This is relevant to current clinical diagnostic practice but with potential future roles to optimize the selection of patients for innovative therapies. At the same time, strict validation of antibodies, assays, scoring systems, and intra- and interobserver reproducibility is needed.

Clinical activity of crizotinib in lung adenocarcinoma harboring a HLA_A‑ROS1 rearrangement: A case report

The benefits of crizotinib therapy in patients with tyrosine receptor kinase ROS proto-oncogene 1 (ROS1)-rearranged non-small cell lung cancer (NSCLC) have been demonstrated. The present study reports a 47-year-old woman with lung adenocarcinoma harboring a rare HLA_A-ROS1 rearrangement with clinical response to crizotinib. To the best of our knowledge there have been no reports of HLA_A-ROS1-rearranged lung cancer regarding clinical course and the efficacy of treatment with crizotinib. A good response to crizotinib therapy in the present case could be a reference for the treatment and prognosis of ROS1-rearranged NSCLC with the same fusion partner. The current report will remind oncologists and pulmonologists to consider the importance of accurate multigene panel assays for detecting driver oncogenes in treating patients with NSCLC.

Concurrent classic driver oncogenes mutation with ROS1 rearrangement predicts superior clinical outcome in NSCLC patients

BACKGROUND

There is high mortality rate and poor prognosis in lung cancer, especially non-small-cell lung cancer (NSCLC). Recent study showed that concurrent classic driver oncogene mutation with ROS1 rearrangement was found in NSCLC patients. However, whether this would affect the development and prognosis of NSCLC is still unclear.

OBJECTIVE

To explore the clinical characteristics and prognosis of NSCLC patients harboring concurrent classic driver oncogene mutation with ROS1 rearrangement.

METHODS

A retrospective study was conducted on 220 patients diagnosed with NSCLC. All samples were screened for EGFR and KRAS using amplification-refractory mutation system assay, and for ALK, ROS1 using RT-PCR. The clinical characteristics and clinical outcomes of concurrent gene alterations with ROS1 rearrangement were analyzed.

RESULTS

In 220 patients, 12 (5.45%) were ROS1 rearrangement, who tend to be younger, non-smokers. The mutation rates of EGFR, KRAS, ALK and ROS1 in NSCLC were 28.64%, 1.82%, 3.64% and 5.45%, respectively. ROS1 rearrangement was identified to co-occur in 5 (2.27%) NSCLC patients. ROS1/EGFR co-alterations were found in 3.17% of NSCLC patients, 16.67% of ROS1-positive NSCLC patients. Concomitant ROS1/ALK rearrangement constituted 37.50% in ALK-positive patients, and 25.00% in ROS1-positive patients. SDC4-ROS1 was the most common fusion partner in concurrent ROS1 rearrangement patients. The median overall survival of NSCLC with concurrent ROS1 rearrangement group and single ROS1 rearrangement group were 25 months and 14 months.

CONCLUSION

Concurrent driver oncogenes mutation with ROS1 rearrangement defines a unique subgroup of NSCLC. Patients with concomitant ROS1 rearrangement might have a better prognosis.

Comparison of ROS1-rearrangement detection methods in a cohort of surgically resected non-small cell lung carcinomas

Background

Patients with non-small cell lung cancer (NSCLC) harboring a ROS proto-oncogene 1 (ROS1)-rearrangement respond to treatment with ROS1 inhibitors. To distinguish these rare cases, screening with immunohistochemistry (IHC) for ROS1 protein expression has been suggested. However, the reliability of such an assay and the comparability of the antibody clones has been debated. Therefore we evaluated the diagnostic performance of current detection strategies for ROS1-rearrangement in two NSCLC-patient cohorts.

Methods

Resected tissue samples, retrospectively collected from consecutive NSCLC-patients surgically treated at Uppsala University Hospital were incorporated into tissue microarrays [all n=676, adenocarcinomas (AC) n=401, squamous cell carcinomas (SCC) n=213, other NSCLC n=62]. ROS1-rearrangements were detected using fluorescence in situ hybridization (FISH) (Abbott Molecular; ZytoVision). In parallel, ROS1 protein expression was detected using IHC with three antibody clones (D4D6, SP384, EPMGHR2) and accuracy, sensitivity, and specificity were determined. Gene expression microarray data (Affymetrix) and RNA-sequencing data were available for a subset of patients. NanoString analyses were performed for samples with positive or ambiguous results (n=21).

Results

Using FISH, 2/630 (0.3% all NSCLC; 0.5% non-squamous NSCLC) cases were positive for ROS1 fusion. Additionally, nine cases demonstrated ambiguous FISH results. Using IHC, ROS1 protein expression was detected in 24/665 (3.6% all NSCLC; 5.1% non-squamous NSCLC) cases with clone D4D6, in 18/639 (2.8% all NSCLC; 3.9% non-squamous NSCLC) cases with clone SP384, and in 1/593 (0.2% all NSCLC; 0.3% non-squamous NSCLC) case with clone EPMGHR2. Elevated RNA-levels were seen in 19/369 (5.1%) cases (Affymetrix and RNA-sequencing combined). The overlap of positive results between the assays was poor. Only one of the FISH-positive cases was positive with all antibodies and demonstrated high RNA-expression. This rearrangement was confirmed in the NanoString-assay and also in the RNA-sequencing data. Other cases with high protein/RNA-expression or ambiguous FISH were negative in the NanoString-assay.

Conclusions

The occurrence of ROS1 fusions is low in our cohorts. The IHC assays detected the fusions, but the accuracy varied depending on the clone. The presumably false-positive and uncertain FISH results questions this method for detection of ROS1-rearrangements. Thus, when IHC is used for screening, transcript-based assays are preferable for validation in clinical diagnostics.

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.

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.

Predictive molecular pathology of lung cancer in Germany with focus on gene fusion testing: Methods and quality assurance

Predictive molecular testing has become an important part of the diagnosis of any patient with lung cancer. Using reliable methods to ensure timely and accurate results is inevitable for guiding treatment decisions. In the past few years, parallel sequencing has been established for mutation testing, and its use is currently broadened for the detection of other genetic alterations, such as gene fusion and copy number variations. In addition, conventional methods such as immunohistochemistry and in situ hybridization are still being used, either for formalin-fixed, paraffin-embedded tissue or for cytological specimens. For the development and broad implementation of such complex technologies, interdisciplinary and regional networks are needed. The Network Genomic Medicine (NGM) has served as a model of centralized testing and decentralized treatment of patients and incorporates all German comprehensive cancer centers. Internal quality control, laboratory accreditation, and participation in external quality assessment is mandatory for the delivery of reliable results. Here, we provide a summary of current technologies used to identify patients who have lung cancer with gene fusions, briefly describe the structures of NGM and the national NGM (nNGM), and provide recommendations for quality assurance.

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.

Precision medicine in non-small cell lung cancer: Current applications and future directions

Advances in biomarkers, targeted therapies, and immuno-oncology have transformed the clinical management of patients with advanced NSCLC. For oncogene-driven tumors, there are highly effective targeted therapies against EGFR, ALK, ROS1, BRAF, TRK, RET, and MET. In addition, investigational therapies for KRAS, NRG1, and HER2 have shown promising results and may become standard-of-care in the near future. In parallel, immune-checkpoint therapy has emerged as an indispensable treatment modality, especially for patients lacking actionable oncogenic drivers. While PD-L1 expression has shown modest predictive utility, biomarkers for immune-checkpoint inhibition in NSCLC have remained elusive and represent an area of active investigation. Given the growing importance of biomarkers, optimal utilization of small tissue biopsies and alternative genotyping methods using circulating cell-free DNA have become increasingly integrated into clinical practice. In this review, we will summarize the current landscape and emerging trends in precision medicine for patients with advanced NSCLC with a special focus on predictive biomarker testing.

Clinical characteristics of patients with ROS1 gene rearrangement in non-small cell lung cancer: a meta-analysis

BACKGROUND

ROS1 gene rearrangement has been reported in several types of cancers, including non-small cell lung cancer (NSCLC). It is reported that tyrosine kinase inhibitors are effective in the treatment of ROS1-rearranged NSCLC. Therefore, the identification of ROS1 rearrangement can be used as potential therapeutic target in lung cancer. Epidemiological data indicates that ROS1 gene rearrangement occurs in approximately 1-2% of NSCLC patients. The small sample sizes of the existing associated studies only represent the characteristics of patients in specific regions or countries, and there is still no latest statistical analysis on ROS1 gene rearrangement anywhere in the world.

METHODS

We conducted a systematic search of the PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), CBM, CNKI, Wanfang, and VIP databases to identify studies on ROS1 gene rearrangement in NSCLC patients from January 1, 2015 to October 27, 2019. We conducted a meta-analysis to investigate the relationship between ROS1 gene rearrangement and clinical characteristics of NSCLC patients. The four clinical features are as follows: gender, smoking status, pathological type, and lung cancer stage.

RESULTS

Thirty-nine studies constituting of 25,055 NSCLC patients were eligible for inclusion in this meta-analysis. A prominently higher rate of ROS1 gene rearrangement was observed in female NSCLC patients (OR =1.94, 95% CI: 1.62-2.32%, P<0.05), patients with no smoking history (OR =2.82, 95% CI: 2.24-3.55%, P<0.05), patients with adenocarcinoma (OR =1.55, 95% CI: 1.14-2.11%, P<0.05), and patients with stage III-IV disease (OR =1.50, 95% CI: 1.15-1.94%, P<0.05). Our meta-analysis also showed that the prevalence of ROS1 rearrangement in adenocarcinoma was 2.49% (95% CI: 1.92-3.11%), while it was lower in non-adenocarcinoma patients (1.37%).

CONCLUSIONS

ROS1 gene rearrangement was more predominant in female patients, patients without smoking history, patients with adenocarcinoma and patients with advanced-stage disease (stages III to IV).

Crizotinib vs platinum-based chemotherapy as first-line treatment for advanced non-small cell lung cancer with different ROS1 fusion variants

BACKGROUND

ROS1 gene fusion represents a specific subtype of non-small cell lung cancer (NSCLC). Crizotinib is recommended for ROS1-positive NSCLC due to its favorable outcome in published clinical trials. However, due to the low incidence of ROS1-positive NSCLC, there is limited information on real-world clinical outcomes in patients treated with either crizotinib or platinum-based doublet chemotherapy.

METHODS

Outcomes were recorded in 102 patients with stage Ⅲb or Ⅳ NSCLC who were treated at four Chinese hospitals between April, 2010 and June, 2019.

RESULTS

Of the 102 patients followed, 71.6% were females, 81.4% were non-smokers, and 98.0% had adenocarcinoma. First-line treatment with crizotinib achieved a significantly longer median progression-free survival (PFS) compared with platinum-based chemotherapy (14.9 months vs 8.5 months, respectively; P < .001). Next-generation sequencing (NGS) identified 61 patients who had ROS1 fusion variants, including CD74 (n = 33) and non-CD74 (n = 28) variants. In patients harboring CD74 fusion variants, the median PFS with first-line crizotinib treatment was significantly longer than in those harboring non-CD74 fusion variants (20.1 months vs 12.0 months, respectively; P = .046). However, in patients treated with platinum-based chemotherapy, there was no significant difference in PFS between the CD74 and non-CD74 variant groups (8.6 months vs 4.3 months, respectively; P = .115). Overall survival (OS) was not reached.

CONCLUSIONS

First-line therapy with crizotinib is more beneficial than platinum-based chemotherapy in patients with advanced NSCLC with different ROS1 fusion variants. Patients harboring CD74 fusion variants appear to respond better to crizotinib.

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.

Knockdown of ROS proto-oncogene 1 inhibits migration and invasion in gastric cancer cells by targeting the PI3K/Akt signaling pathway

Objectives

Gastric cancer ranks the fourth most common cancer and the third leading cause of cancer mortality in the world. ROS proto-oncogene 1 (ROS1) is an oncogene and ROS1 rearrangement has been reported in many cancers. Our study aimed to investigate the potential function and the precise mechanisms of ROS1 in gastric cancer.

Methods

In our study, the analysis of ROS1 expression and clinical pathologic factors of gastric cancer in gastric cancer using TCGA database demonstrated that ROS1 expression was elevated in gastric cancer and related to T, N, M and TNM staging. High expression of ROS1 predicted poor survival in patients with gastric cancer. Then, we measured ROS1 expression in four human gastric cancer cell lines and knocked down ROS1 expression in BGC-823 and SGC-7901 cells by specific shRNA transfection via Lipofectamine 2000. The effect of ROS1 knockdown on cell proliferation, cell cycle distribution, cell apoptosis and metastasis in vitro was evaluated by MTT, colony formation, flow cytometric analysis, wound healing and Transwell invasion assays. The levels of apoptosis-related proteins, EMT markers and the PI3K/Akt signaling pathway members were measured by Western blotting.

Results

We demonstrated that shROS1 transfection markedly downregulated ROS1 expression in BGC-823 and SGC-7901 cells. Knockdown of ROS1 inhibited cell survival, clonogenic growth, migration, invasion and epithelial–mesenchymal transition (EMT), as well as induced cell cycle arrest and apoptosis in gastric cancer cells. Furthermore, ROS1 knockdown inhibited the phosphorylation of PI3K and Akt.

Conclusion

Collectively, our data suggest that ROS1 may serve as a promising therapeutic target in gastric cancer treatment.

Comparison of in Situ and Extraction-Based Methods for the Detection of ROS1 Rearrangements in Solid Tumors

Clinical data confirmed that patients with ROS1 rearrangement are sensitive to specific inhibitors. Therefore, reliable detection of ROS1 rearrangements is essential. Several diagnostic techniques are currently available. However, previous studies were hampered by the low number of ROS1-positive samples. Thirty-five samples, including 32 ROS1 fluorescent in situ hybridization (FISH)-positive and three ROS1 FISH-negative samples were evaluated by ROS1 chromogenic in situ hybridization, ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) immunohistochemistry (IHC), an Agilent SureSelect^{XT HS} custom panel, the Archer FusionPlex Comprehensive Thyroid and Lung panel, and a custom NanoString fusion panel. Some samples were additionally analyzed with the Illumina TruSight Tumor 170 assay. Eleven samples were ROS1 FISH positive by a break-apart signal pattern. In all 11 samples, a ROS1 fusion was confirmed by at least one other method. The other 21 samples tested ROS1 FISH positive by an isolated 3' green signal pattern. Ten of 21 samples could be confirmed by at least two other methods. The other 11 samples tested negative by ROS1 IHC and at least one other method, indicating a false-positive ROS1 FISH result. Our study found that all ROS1 FISH-positive samples with isolated 3' green signals should be confirmed by another method. When sufficient material is available, extraction-based parallel sequencing approaches for the verification of these cases might be preferable.

High feasibility of cytological specimens for detection of ROS1 fusion by reverse transcriptase PCR in Chinese patients with advanced non-small-cell lung cancer

Purpose

Our previous study demonstrated that cytological specimens can be used as alternative samples for detecting anaplastic lymphoma kinase (ALK) fusion with the method of reverse transcriptase PCR (RT-PCR) in patients with advanced non-small-cell lung cancer (NSCLC). The current study aimed to investigate the feasibility of cytological specimens for ROS proto-oncogene 1, receptor tyrosine kinase (ROS1) fusion detection by RT-PCR in advanced NSCLC patients.

Patients and methods

A total of 2,538 patients with advanced NSCLC, including 2,101 patients with cytological specimens and 437 patients with tumor tissues, were included in this study. All patients were screened for ROS1 fusion status by RT-PCR. The efficacy of crizotinib treatment was evaluated in ROS1 fusion-positive NSCLC patients.

Results

Among 2,101 patients with cytological specimens, the average concentration of RNA acquired from cytological specimens was 47.68 ng/μL (95% CI, 43.24–52.62), which was lower than the average of 66.54 ng/μL (95% CI, 57.18–76.60, P=0.001) obtained from 437 tumor tissues. Fifty-five patients harbored ROS1 fusion gene that was detected by RT-PCR, and 14 of them were treated with crizotinib. The incidence of ROS1 fusion was 1.95% (41/2,101) in 2,101 patients with cytological specimens, similar to the rate of 3.20% (14/437, P=0.102) for the 437 patients with tumor tissue. Regarding crizotinib treatment, no statistically significant differences were observed in the objective response rate (ORR) (81.8% vs 100%, P=0.604) between the cytological and tissue subgroups of ROS1-positive patients.

Conclusion

This study shows that cytological specimens can be utilized as alternative samples for ROS1 fusion detection by RT-PCR in advanced NSCLC patients.

Comparison of Molecular Testing Modalities for Detection of ROS1 Rearrangements in a Cohort of Positive Patient Samples

INTRODUCTION

ROS1 gene fusions are a well-characterized class of oncogenic driver found in approximately 1% to 2% of NSCLC patients. ROS1-directed therapy in these patients is more efficacious and is associated with fewer side effects compared to chemotherapy and is thus now considered standard-of-care for patients with advanced disease. Consequently, accurate detection of ROS1 rearrangements/fusions in clinical tumor samples is vital. In this study, we compared the performance of three common molecular testing approaches on a cohort of ROS1 rearrangement/fusion-positive patient samples.

METHODS

Twenty-three ROS1 rearrangement/fusion-positive clinical samples were assessed by at least two of the following molecular testing methodologies: break-apart fluorescence in situ hybridization, DNA-based hybrid capture library preparation followed by next-generation sequencing (NGS), and RNA-based anchored multiplex polymerase chain reaction library preparation followed by NGS.

RESULTS

None of the testing methodologies demonstrated 100% sensitivity in detection of ROS1 rearrangements/fusions. Fluorescence in situ hybridization results were negative in 2 of 20 tested samples, the DNA-based NGS assay was negative in 4 of 18 tested samples, and the RNA-based NGS assay was negative in 3 of 19 tested samples. For all three testing approaches, we identified assay characteristics that likely contributed to false-negative results. Additionally, we report that genomic breakpoints are an unreliable predictor of breakpoints at the transcript level, likely due to alternative splicing.

CONCLUSIONS

ROS1 rearrangement/fusion detection in the clinical setting is complex and all methodologies have inherent limitations of which users must be aware to correctly interpret results.

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.

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.

ROS1 [corrected]

ROS1 is a receptor tyrosine kinase that has recently been shown to undergo gene rearrangements in~1%-2% of non-small cell lung carcinoma (NSCLC) and in a variety of other tumours including cholangiocarcinoma, gastric carcinoma, colorectal carcinoma and in spitzoid neoplasms, glioblastoma and inflammatory myofibroblastic tumours. The ROS1 gene fusion undergoes constitutive activation, regulates cellular proliferation and is implicated in carcinogenesis. ROS1 fusions can be detected by fluorescence in situ hybridisation, real-time PCR, sequencing-based techniques and immunohistochemistry-based methods in clinical laboratories. The small molecule tyrosine kinase inhibitor, crizotinib has been shown to be an effective inhibitor of ROS1 and has received Food and Drug Administration approval for treatment of advanced NSCLC. The current review is an update on the clinical findings and detection methods of ROS1 in clinical laboratories in NSCLC and other tumours.

Detection of ROS1 rearrangement in non-small cell lung cancer: current and future perspectives

ROS1 rearrangement characterizes a small subset (1%-2%) of non-small cell lung cancer and is associated with slight/never smoking patients and adenocarcinoma histology. Identification of ROS1 rearrangement is mandatory to permit targeted therapy with specific inhibitors, demonstrating a significantly better survival when compared with conventional chemotherapy. Detection of ROS1 rearrangement is based on in situ (immunohistochemistry, fluorescence in situ hybridization) and extractive non-in situ assays. While fluorescence in situ hybridization still represents the gold standard in clinical trials, this technique may fail to recognize rearrangements of ROS1 with some gene fusion partner. On the other hand, immunohistochemistry is the most cost-effective screening technique, but it seems to be characterized by low specificity. Extractive molecular assays are expensive and laborious methods, but they specifically recognize almost all ROS1 fusions using a limited amount of mRNA even from formalin-fixed, paraffin-embedded tumor tissues. This review is a discussion on the present and futuristic diagnostic scenario of ROS1 identification in lung cancer.

Immunohistochemistry of Pulmonary Biomarkers: A Perspective From Members of the Pulmonary Pathology Society

The use of immunohistochemistry for the determination of pulmonary carcinoma biomarkers is a well-established and powerful technique. Immunohistochemisty is readily available in pathology laboratories, is relatively easy to perform and assess, can provide clinically meaningful results very quickly, and is relatively inexpensive. Pulmonary predictive biomarkers provide results essential for timely and accurate therapeutic decision making; for patients with metastatic non-small cell lung cancer, predictive immunohistochemistry includes ALK and programmed death ligand-1 (PD-L1) (ROS1, EGFR in Europe) testing. Handling along proper methodologic lines is needed to ensure patients receive the most accurate and representative test outcomes.

Nonsmall cell lung carcinoma: diagnostic difficulties in small biopsies and cytological specimens

The pathological and molecular classification of lung cancer has become substantially more complex over the past decade. For diagnostic purposes on small samples, additional stains are frequently required to distinguish between squamous cell carcinoma and adenocarcinoma. Subsequently, for advanced nonsquamous cell nonsmall cell lung carcinoma (NSCLC) patients, predictive analyses on epidermal growth factor receptor, anaplastic lymphoma kinase and ROS1 are required. In NSCLCs negative for these biomarkers, programmed death ligand-1 immunohistochemistry is performed. Small samples (biopsy and cytology) require “tissue” management, which is best achieved by the interaction of all physicians involved.