MA26.07 ROS1 (SP384) Immunohistochemistry Inter-Reader Precision Between 12 Pathologists

Efficient Identification of Patients With NTRK Fusions Using a Supervised Tumor-Agnostic Approach

CONTEXT.—

The neurotrophic tropomyosin receptor kinase (NTRK) family gene rearrangements have been recently incorporated as predictive biomarkers in a "tumor-agnostic" manner. However, the identification of these patients is extremely challenging because the overall frequency of NTRK fusions is below 1%. Academic groups and professional organizations have released recommendations on the algorithms to detect NTRK fusions. The European Society for Medical Oncology proposal encourages the use of next-generation sequencing (NGS) if available, or alternatively immunohistochemistry (IHC) could be used for screening with NGS confirmation of all positive IHC results. Other academic groups have included histologic and genomic information in the testing algorithm.

OBJECTIVE.—

To apply some of these triaging strategies for a more efficient identification of NTRK fusions within a single institution, so pathologists can gain practical insight on how to start looking for NTRK fusions.

DESIGN.—

A multiparametric strategy combining histologic (secretory carcinomas of the breast and salivary gland; papillary thyroid carcinomas; infantile fibrosarcoma) and genomic (driver-negative non-small cell lung carcinomas, microsatellite instability-high colorectal adenocarcinomas, and wild-type gastrointestinal stromal tumors) triaging was put forward.

RESULTS.—

Samples from 323 tumors were stained with the VENTANA pan-TRK EPR17341 Assay as a screening method. All positive IHC cases were simultaneously studied by 2 NGS tests, Oncomine Comprehensive Assay v3 and FoundationOne CDx. With this approach, the detection rate of NTRK fusions was 20 times higher (5.57%) by only screening 323 patients than the largest cohort in the literature (0.30%) comprising several hundred thousand patients.

CONCLUSIONS.—

Based on our findings, we propose a multiparametric strategy (ie, "supervised tumor-agnostic approach") when pathologists start searching for NTRK fusions.

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.

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.

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.

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.