NTRK Gene Fusions Research Articles

Treatment Options in Late-Line Colorectal Cancer: Lessons Learned from Recent Randomized Studies.

Systemic treatment of metastatic colorectal cancer (mCRC) has improved considerably over the past 20 years. First- and second-line combinations of 5FU, oxaliplatin, and irinotecan, with or without anti-angiogenic and/or anti-EGFR antibodies, were approved shortly after the turn of the millennium. Further triumphs were not seen for almost 10 years, until the approval of initially regorafenib and shortly after trifluridine/tipiracil. A growing understanding of tumor biology through molecular profiling has led to further treatment options. Here, we review the most recent clinical data for late-line treatment options in mCRC, focusing on randomized trials if available. We include recommendations for options in unselected patients and therapies that should only be offered in patients with distinct tumor profiles (e.g., BRAF mutations, KRAS G12C mutations, HER2 amplification, deficient MMR, or NTRK gene fusions).

Tyrosine Kinase Inhibitors for Radioactive Iodine Refractory Differentiated Thyroid Cancer.

Patients with differentiated thyroid cancer usually present with early-stage disease and undergo surgery followed by adjuvant radioactive iodine ablation, resulting in excellent clinical outcomes and prognosis. However, a minority of patients relapse with metastatic disease, and eventually develop radioactive iodine refractory disease (RAIR). In the past there were limited and ineffective options for systemic therapy for RAIR, but over the last ten to fifteen years the emergence of tyrosine kinase inhibitors (TKIs) has provided important new avenues of treatment for these patients, that are the focus of this review. Currently, Lenvatinib and Sorafenib, multitargeted TKIs, represent the standard first-line systemic treatment options for RAIR thyroid carcinoma, while Cabozantinib is the standard second-line treatment option. Furthermore, targeted therapies for patients with specific targetable molecular abnormalities include Latrectinib or Entrectinib for patients with NTRK gene fusions and Selpercatinib or Pralsetinib for patients with RET gene fusions. Dabrafenib plus Trametinib currently only have tumor agnostic approval in the USA for patients with BRAF V600E mutations, including thyroid cancer. Redifferentiation therapy is an area of active research, with promising initial results, while immunotherapy studies with checkpoint inhibitors in combination with tyrosine kinase inhibitors are underway.

10031-GGE-2 GENOMIC ANALYSIS OF MENINGIOMA USING GENE PANEL TESTING

Abstract Recently, cancer gene panel tests have been covered by insurance and their usefulness has been reported. In addition to the cancer gene panel tests covered by insurance, we are conducting the PleSSision-Rapid test, a cancer gene panel test that can measure 143 genes, as a clinical research project. The former has been used for 14 cases brain tumors, and the latter has been used for brain tumors in about 100 cases, respectively. The PleSSision-Rapid test has now completed analysis of 87 cases, with gliomas accounting for 33, meningiomas for 29, and metastatic brain tumors for 14 cases. Tumor mutation burden (TMB) was high in 18 cases, and microsatellite instability was high in none. NTRK gene fusion was observed in 1 case. Of the 29 meningiomas, 9 were male and 20 female, ranging in age from 31 to 79 years (mean 57). Twenty of the cases were located at the skull base. Twenty four were primary cases, whereas 5 were recurrent cases. WHO grade 1, 2, and 3 were 23, 4, and 2, respectively. There was no difference in TMB among grades, and Ki-67 values increased with increasing grade. Comparing grade 1 and grade 2/3, NF2 and KDM6A were found to be significantly different in the rate of gene mutations. Grade 2/3 patients had a significantly higher frequency of copy number aberrations such as genes related to DNA repair, histone modification, and chromatin remodeling, than grade 1 patients,

Detection of NTRK gene fusions in solid tumors: recommendations from a Latin American group of oncologists and pathologists.

NTRK gene fusions have been detected in more than 25 types of tumors and their prevalence is approximately 0.3% in solid tumors. This low prevalence makes identifying patients who could benefit from TRK inhibitors a considerable challenge. Furthermore, while numerous papers on the evaluation of NTRK fusion genes are available, not all countries have guidelines that are suitable for their setting, as is the case with Latin America. Therefore, a group of oncologists and pathologists from several countries in Latin America (Argentina, Chile, Ecuador, Mexico, Peruand Uruguay) met to discuss and reach consensus on how to identify patients with NTRK gene fusions in solid tumors. To do so, they developed a practical algorithm, considering their specific situation and limitations.

CTNI-75. EFFICACY AND SAFETY OF LAROTRECTINIB IN PATIENTS WITH TROPOMYOSIN RECEPTOR KINASE (TRK) FUSION PRIMARY CENTRAL NERVOUS SYSTEM (CNS) TUMORS: AN UPDATED ANALYSIS

Abstract BACKGROUND Larotrectinib is a highly selective TRK inhibitor approved for tumor-agnostic use in patients with various tumor types, including primary CNS tumors. Here, we report the independent central review and updated data on patients with TRK fusion-positive primary CNS tumors. METHODS Patients with TRK fusion primary CNS tumors enrolled in two clinical trials (NCT02637687, NCT02576431) were included. Responses were independent review committee (IRC)-assessed. RESULTS As of July 2022, 41 patients were eligible for response assessment by IRC. The median age at enrollment was 11 years (range 1-79). Tumor histologic groups included: high-grade glioma (HGG; n=25), low-grade glioma (LGG; n=9), and other (n=7). Sixteen (39%) patients had received ≥ 2 prior systemic therapies. For all patients, objective response rate (ORR) was 22% (95% CI 11–38): one complete response, eight partial response, 20 stable disease, and 12 progressive disease. For pediatric patients (n=28), the ORR was 29% (95% CI 13–49). For pediatric patients with HGG and LGG, ORRs were 14% (95% CI 2–43) and 57% (95% CI 18–90), respectively. The disease control rates at 24 weeks were 54% (95% CI 37–69) and 71% (95% CI 51–87) for all patients and pediatric patients, respectively. Medians for time to response, duration of response, progression-free survival, and overall survival (OS) were 1.9 months, 12.2 months (95% CI 3.7–not estimable), 11.1 months (95% CI 3.6–19.8), and not reached, respectively. The 48-month OS rate was 52%. Treatment duration ranged from 1 to 50+ months. Treatment-related adverse events (TRAEs) were mostly Grade 1/2. No patients discontinued treatment due to TRAEs. CONCLUSION Larotrectinib demonstrated rapid, durable responses and a manageable safety profile in patients with TRK fusion primary CNS tumors. This supports the wider adoption of next-generation sequencing panels that include NTRK gene fusions when testing patients with CNS tumors.

EP13.02-03 Entrectinib Amazing Efficacy in a Case of Lung Atypical Carcinoid with NTRK Gene Fusion

EP13.02-03 Entrectinib Amazing Efficacy in a Case of Lung Atypical Carcinoid with NTRK Gene Fusion

122P Molecular testing, treatment, and response of patients with advanced solid tumors harboring an NTRK gene fusion: Second interim results of the REALTRK registry

122P Molecular testing, treatment, and response of patients with advanced solid tumors harboring an NTRK gene fusion: Second interim results of the REALTRK registry

Larotrectinib efficacy and safety in adult patients with tropomyosin receptor kinase fusion sarcomas.

Larotrectinib, a first-in-class, highly selective tropomyosin receptor kinase (TRK) inhibitor, has demonstrated efficacy in adult and pediatric patients with various solid tumors harboring NTRK gene fusions. This subset analysis focuses on the efficacy and safety of larotrectinib in an expanded cohort of adult patients with TRK fusion sarcomas. Patients (≥18years old) with sarcomas harboring NTRK gene fusions were identified from three clinical trials. Patients received larotrectinib 100mg orally twice daily. Response was investigator-assessed per RECIST v1.1. Data cutoff was July 20, 2021. At the data cutoff, 36 adult patients with TRK fusion sarcomas had initiated larotrectinib therapy: two (6%) patients had bone sarcomas, four (11%) had gastrointestinal stromal tumors, and 30 (83%) had soft tissue sarcomas. All patients were evaluable for response and demonstrated an objective response rate of 58% (95% confidence interval, 41-74). Patients responded well to larotrectinib regardless of number of prior lines of therapy. Adverse events (AEs) were mostly grade 1/2. Grade 3 treatment-emergent AEs (TEAEs) occurred in 15 (42%) patients. There were no grade 4 TEAEs. Two grade 5 TEAEs were reported, neither of which were considered related to larotrectinib. Four (11%) patients permanently discontinued treatment due to TEAEs. Larotrectinib demonstrated robust and durable responses, extended survival benefit, and a favorable safety profile in adult patients with TRK fusion sarcomas with longer follow-up. These results continue to demonstrate that testing for NTRK gene fusions should be incorporated into the clinical management of adult patients with various types of sarcomas. Tropomyosin receptor kinase (TRK) fusion proteins result from translocations involving the NTRK gene and cause cancer in a range of tumor types. Larotrectinib is an agent that specifically targets TRK fusion proteins and is approved for the treatment of patients with TRK fusion cancer. This study looked at how well larotrectinib worked in adult patients with sarcomas caused by TRK fusion proteins. Over half of patients had a durable response to larotrectinib, with no unexpected side effects. These results show that larotrectinib is safe and effective in adult patients with TRK fusion sarcomas.

Cost-Efficient Detection of NTRK1/2/3 Gene Fusions: Single-Center Analysis of 8075 Tumor Samples.

The majority of NTRK1, NTRK2, and NTRK3 rearrangements result in increased expression of the kinase portion of the involved gene due to its fusion to an actively transcribed gene partner. Consequently, the analysis of 5'/3'-end expression imbalances is potentially capable of detecting the entire spectrum of NTRK gene fusions. Archival tumor specimens obtained from 8075 patients were subjected to manual dissection of tumor cells, DNA/RNA isolation, and cDNA synthesis. The 5'/3'-end expression imbalances in NTRK genes were analyzed by real-time PCR. Further identification of gene rearrangements was performed by variant-specific PCR for 44 common NTRK fusions, and, whenever necessary, by RNA-based next-generation sequencing (NGS). cDNA of sufficient quality was obtained in 7424/8075 (91.9%) tumors. NTRK rearrangements were detected in 7/6436 (0.1%) lung carcinomas, 11/137 (8.0%) pediatric tumors, and 13/851 (1.5%) adult non-lung malignancies. The highest incidence of NTRK translocations was observed in pediatric sarcomas (7/39, 17.9%). Increased frequency of NTRK fusions was seen in microsatellite-unstable colorectal tumors (6/48, 12.5%), salivary gland carcinomas (5/93, 5.4%), and sarcomas (7/143, 4.9%). None of the 1293 lung carcinomas with driver alterations in EGFR/ALK/ROS1/RET/MET oncogenes had NTRK 5'/3'-end expression imbalances. Variant-specific PCR was performed for 744 tumors with a normal 5'/3'-end expression ratio: there were no rearrangements in 172 EGFR/ALK/ROS1/RET/MET-negative lung cancers and 125 pediatric tumors, while NTRK3 fusions were detected in 2/447 (0.5%) non-lung adult malignancies. In conclusion, this study describes a diagnostic pipeline that can be used as a cost-efficient alternative to conventional methods of NTRK1-3 analysis.

Uterine Sarcoma With EML4::NTRK3 Fusion: A Spectrum of Mesenchymal Neoplasms Harboring Actionable Gene Fusions.

NTRK gene fusions are part of a paradigm shift in oncology, arising as one of the main genomic alterations with actionability in the so-called "agnostic setting." In gynecologic pathology, the recent description of uterine sarcoma resembling fibrosarcoma and with NTRK rearrangements (NTRK-rearranged uterine sarcoma) highlights the importance of recognizing clinicopathological cues that can lead to genomic profiling. Herein, we report the case of a 43-year-old woman presenting with vaginal bleeding and pelvic mass. Histopathology of the tumor showed moderately atypical spindle cells arranged in long fascicles reminiscent of fibrosarcoma, along with immunohistochemical positivity for S100, CD34, and pan-tropomyosin receptor kinase. This prompted RNA-sequencing and the finding of a rare EML4::NTRK3 fusion. Clinical, histologic, and molecular findings are described, in addition to discussions regarding differential diagnoses and possible implications of the findings in clinical practice.

NTRK fusion events and targeted treatment of advanced radioiodine refractory thyroid cancer

PurposePathogenic fusion events involving neurotrophic receptor tyrosine kinase (NTRK) have been described in ~ 2% of differentiated thyroid cancer (DTC). The selective tropomyosin receptor kinase (TRK) inhibitors entrectinib and larotrectinib have been approved in a tumor agnostic manner based on phase 1/2 clinical trials. In a real-world setting at five referral centers, we aimed to describe the prevalence of NTRK gene fusions and the efficacy and safety of TRK inhibitor treatment for non-medullary, advanced thyroid cancer (TC).MethodsA total of 184 TC patients with testing for NTRK gene fusions were included. Progression-free survival (PFS) and overall survival (OS) probabilities were estimated using the Kaplan–Meier method in six patients with NTRK fusion-positive TC who underwent TRK inhibitor therapy.Results8/184 (4%) patients harbored NTRK gene fusions. Six patients with radioiodine (RAI)-refractory TC harboring NTRK1 (n = 4) and NTRK3 (n = 2) gene fusions were treated with larotrectinib. Five patients (83%) had received ≥ 1 prior systemic therapy and one patient did not receive prior systemic therapy. All patients had morphologically progressive disease before treatment initiation. Objective response rate was 83%, including two complete remissions. Median PFS from start of TRK inhibitor treatment was 23 months (95% confidence interval [CI], 0–57.4) and median OS was not reached (NR) (95% CI, NR). Adverse events were of grade 1–3.ConclusionThe prevalence of NTRK gene fusions in our cohort of RAI-refractory TC is slightly higher than reported for all TC patients. Larotrectinib is an effective treatment option in the majority of NTRK gene fusion-positive advanced TC patients after prior systemic treatment and has a favorable safety profile.

An application of extrapolating clinical data from single-arm trials to assess comparative effectiveness.

6614 Background: Single arm studies pose some challenges to determining comparative effectiveness of treatments. Such is the case with the tumor agnostic tropomyosin receptor kinase (TRK) inhibitors, larotrectinib and entrectinib. Larotrectinib and entrectinib are indicated for treatment of advanced cancer in patients (pts) with NTRK gene fusions. Lacking head-to-head trials, modeling methods are useful to estimate relative benefit. A direct naïve comparison, where single arms from separate trials are compared, can be used. Here, we estimate and compare long term benefit for pts receiving larotrectinib or entrectinib for NTRK gene fusion-positive non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) by extrapolating survival curves to generate expected life-years (LYs) and quality-adjusted life-years (QALYs). Methods: We used partitioned survival methods to forecast comparative effectiveness. Larotrectinib survival data were derived from an updated July 2021 analysis of 21 adults (≥18 years of age) with NSCLC and 15 pts with CRC (NCT02122913, NCT02637687, and NCT02576431). Survival data for entrectinib were derived from published literature. Extrapolation of results were necessary to estimate long-term outcomes since the mean follow-up was less than three years. Progression free survival and overall survival for both treatments were estimated using several parametric survival distributions (Exponential, Weibull, Log-logistic, and Log-normal), then selecting based on AIC and clinical plausibility. QALYs were estimated by adjusting the time spent in the pre progression and post progression health states by utility values from the literature. A discount rate of 3% was applied to LYs and QALYs. Model uncertainty was evaluated using one-way and probabilistic sensitivity analyses. Results: In the larotrectinib trials, response rates were 86% and 33% in NSCLC and CRC, respectively. Exponential curves were fit for both treatments. In the entrectinib trials, response rates were 70% in NSCLC and 29% in CRC. The larotrectinib model estimated 7.3 LYs (95% Credible Interval [CrI]: 3.3, 11.4) and 4.3 QALYs (95% CrI: 2.2, 6.5) in NSCLC and 1.7 LYs (95% CrI: 0.8, 3.2) and 1.3 QALYs (95% CrI: 0.7, 2.3) in CRC. The entrectinib model estimated 2.7 LYs (95% CrI: 1.7, 4.2) and 1.6 QALYs (95% CrI: 1.1, 2.3) in NSCLC and 0.5 LYs (95% CrI: 0.2, 1.6) and 0.4 QALYs (95% CrI: 0.1, 1.1). Compared to entrectinib, larotrectinib produced additional gains of 4.7 LYs and 2.7 QALYs in NSCLC and 1.1 LYs and 0.9 QALYs in CRC. Limitations include non-matched baseline differences in the trial populations. Conclusions: In the absence of head-to-head trials, comparative effectiveness can be assessed by extrapolating from single armed studies indicated for the same patient population. Larotrectinib improved survival and quality adjusted survival vs entrectinib. Additional studies are needed to confirm these findings.

SA22 The Complexity Of Finding Fit-For-Purpose Real-World Data on Oncology Patients with Rare NTRK Gene Fusions and a Novel Solution

NTRK gene fusions are rare oncogenic drivers, occurring in only approximately 0.30% of solid tumors, for which there are currently 2 approved therapies based on single-arm trials. Finding real world data (RWD) that are suitable for comparison is challenging, due to the absence of genomic information in traditional RWD data sources and the rarity of patients with NTRKgene fusion-positive (NTRK+) tumors seen by clinical sites. We explored an innovative, multi-faceted approach to build a real-world dataset of patients with NTRK+ solid tumors.

CO212 The Potential Long-Term Comparative Effectiveness of Larotrectinib Vs. Immune Checkpoint Inhibitors for Treatment of Metastatic NTRKGene Fusion-Positive Cancers

Larotrectinib is approved for patients with advanced NTRK gene fusion-positive solid tumors. Some studies have demonstrated promising results with larotrectinib compared to systemic therapy. However, a comparison to checkpoint inhibitors such as nivolumab or pembrolizumab has not been done. Our objective was to estimate and compare expected life-years (LYs) and quality-adjusted life-years (QALYs) for patients with non-small cell lung cancer (NSCLC) eligible for larotrectinib vs. patients with unknown NTRK gene fusion status on nivolumab or pembrolizumab. We also looked at patients with metastatic differentiated thyroid cancer (DTC) as pembrolizumab may be considered in certain circumstances.

Phase 2 study of larotrectinib in children with newly diagnosed infantile fibrosarcoma (IFS): Children’s Oncology Group (COG) ADVL1823 cohort A.

10008 Background: NTRK1/2/3 gene fusions (TRK fusions) occur in a range of pediatric cancers and are the canonical molecular alterations in IFS. Larotrectinib is a highly selective TRK inhibitor that is FDA-approved for TRK fusion solid tumors in patients with no satisfactory alternative treatments or whose cancer has progressed following initial treatment. ADVL1823 (NCT03834961) evaluated larotrectinib in children with newly diagnosed TRK fusion positive solid tumors in two histology-based cohorts. Cohort A enrolled patients with IFS and is the focus of this analysis. Methods: Newly diagnosed patients ≤30 years old with unresectable or metastatic IFS and a locally identified NTRK gene fusion were eligible for Cohort A utilizing a Simon 2-stage design. Patients received larotrectinib at a dose of 100 mg/m2/dose BID (max of 100 mg/dose) continuously in 28-day cycles until disease progression, unacceptable toxicity, the tumor becoming surgically resectable following a minimum of 6 cycles of therapy, or completion of 12 cycles (for those with CR) or 26 cycles (for those with PR) of therapy. The primary endpoint was the centrally confirmed objective response rate within 6 cycles according to RECIST 1.1; response assessment occurred every 2 cycles for the first 6 cycles. The data cutoff was December 31, 2022. Results: Between October 2019 and May 2022, 18 patients with IFS were enrolled from 14 centers. The median age was 2 months (range <1 month to 4.6 years). NTRK fusions included presumed/confirmed ETV6: NTRK3, n=15, NTRK3 (partner unconfirmed), TMP3: NTRK1 and DCTN1: NTRK1, n=1 each, and were identified by FISH (n=8), NGS (n=7), and PCR (n=3). 17 of 18 patients (94%) demonstrated confirmed objective responses (16 PR and 1 CR,) resulting in closure to enrollment after meeting the pre-specified efficacy threshold. The only patient without confirmed response demonstrated 79% tumor reduction after cycle 2, but no confirmatory scan was obtained within the first 6 cycles. No patient discontinued therapy within the first 6 cycles due to disease progression or toxicity. Four (22%) patients had dose limiting toxicities: 2 neutropenia (both CTCAE V5 grade (G)4) and 1 each G3 AST increase and G3 weight loss. All patients resumed therapy following a dose reduction. Treatment-related grade ≥ 3 toxicities occurred in 7 patients, most commonly neutropenia (n=5, 3 G3, 2 G4). Conclusions: Larotrectinib is highly active and well tolerated in newly diagnosed patients with IFS. Enrollment of this very rare molecularly defined patient population was feasible within the COG. Ongoing follow-up will evaluate durability of response after treatment discontinuation at protocol specified response-adapted timepoints with or without surgical resection of tumor. Clinical trial information: NCT03834961 .

Retrospective analysis of genetically matched therapies in salivary gland cancer entities using a real-world database in a tertiary salivary gland cancer expertise center.

6098 Background: Salivary gland cancer (SGC) is a rare cancer and includes twenty-two different entities. In the Radboudumc SGC expertise center, a real-word database was set up to uniformly collect data of SGC subtypes. More than 500 SGC patients have been enrolled and collection of data for 261 patients is currently completed. Here, we describe the retrospective analysis of genetic aberrations found in different SGC entities and the treatment of selected recurrent/metastatic (R/M) patients with genetically matched therapies (GMT). Methods: All SGC patients in the SGC registry of Radboudumc between 2017 and 2022 whose tumors underwent next generation sequencing (NGS) and/or gene fusion analysis within standard of care or clinical trial were included in this analysis. Both primary tumor specimen and metastatic tissue have been used for molecular analyses. GMT was given in basket trials or on basis of compassionate use for clinically relevant genetic aberrations that are considered actionable nowadays. Results: NGS and/or gene fusion analysis data was available for 162 out of 261 patients, and most frequently in salivary duct carcinoma (SDC) patients (82/162). The number of patients with genetic aberrations differed between SGC entities. In 112 patients at least one genetic aberration and/or gene fusion was detected regardless of whether the target was druggable. Ninety-three patients out of 112 patients had R/M disease. Both a gene fusion and one or more mutations were found in six patients (adenoid cystic carcinoma [AdCC], n = 3; SDC, n = 2; and secretary carcinoma [SC], n = 1;). Depending on the SGC subtype, in 14.3 – 100% of the R/M cases with genetic aberrations and/or gene fusions a GMT was started (SDC, 14/60; AdCC, 3/21; SC, 2/2; mucoepidermoid carcinoma, 2/4). The most given GMT among patients were monoclonal antibodies and tyrosine kinase inhibitors (TKI), respectively in nine and eleven patients, moreover immunotherapy was started in one patient. For example, eight SDC patients were treated with ERBB2 targeting agents (4/8 mutations; 4/8 copy number variants in ERBB2), showing a complete response in three patients. Additionally, one partial response and two stable diseases were observed, two patients were lost of follow-up. Two SC patients treated with a TKI based on the presence of the ETV6- NTRK gene fusion showed radiologically a partial response. Conclusions: In 69% of the SGC patients at least one genetic aberration and/or gene fusion was found, and in 23% of the R/M cases GMT was administered. Response differs between entities and GMT; a complete response was achieved after initiation of GMT in several patients. These data justify the use of NGS and gene fusion analysis in all salivary gland cancer entities, notably in subtypes lacking standard systemic therapies as this could offer other therapeutic options.

NTRK fusions: A novel diagnostic and therapeutic methodology for cancer

This commentary discusses the case from the publication “Metastatic Triple Negative Breast Cancer with NTRK Gene Fusion on Tissue but not on ctDNA Molecular Profile.” This paper stresses the importance of molecular profiling to find characteristic mutations such as NTRK gene fusions which increase therapeutic options including tyrosine receptor kinase inhibitors such as Larotrectinib and entrectinib. The current profiling techniques are also discussed with both advantages and limitations discussed. Genomic testing in relation to current pharmaceutical therapies will shape the future of cancer diagnosis and treatment.

ERBB family fusions are recurrent and actionable oncogenic targets across cancer types.

Gene fusions involving receptor tyrosine kinases (RTKs) define an important class of genomic alterations with many successful targeted therapies now approved for ALK, ROS1, RET and NTRK gene fusions. Fusions involving the ERBB family of RTKs have been sporadically reported, but their frequency has not yet been comprehensively analyzed and functional characterization is lacking on many types of ERBB fusions. We analyzed tumor samples submitted to Caris Life Sciences (n=64,354), as well as the TCGA (n=10,967), MSK IMPACT (n=10,945) and AACR GENIE (n=96,324) databases for evidence of EGFR, ERBB2 and ERBB4 gene fusions. We also expressed several novel fusions in cancer cell lines and analyzed their response to EGFR and HER2 tyrosine kinase inhibitors (TKIs). In total, we identified 1,251 ERBB family fusions, representing an incidence of approximately 0.7% across all cancer types. EGFR, ERBB2, and ERBB4 fusions were most frequently found in glioblastoma, breast cancer and ovarian cancer, respectively. We modeled two novel types of EGFR and ERBB2 fusions, one with a tethered kinase domain and the other with a tethered adapter protein. Specifically, we expressed EGFR-ERBB4, EGFR-SHC1, ERBB2-GRB7 and ERBB2-SHC1, in cancer cell lines and demonstrated that they are oncogenic, regulate downstream signaling and are sensitive to small molecule inhibition with EGFR and HER2 TKIs. We found that ERBB fusions are recurrent mutations that occur across multiple cancer types. We also establish that adapter-tethered and kinase-tethered fusions are oncogenic and can be inhibited with EGFR or HER2 inhibitors. We further propose a nomenclature system to categorize these fusions into several functional classes.

Consensus Recommendations to Optimize the Detection and Reporting of NTRK Gene Fusions by RNA-Based Next-Generation Sequencing.

The detection of gene fusions by RNA-based next-generation sequencing (NGS) is an emerging method in clinical genetic laboratories for oncology biomarker testing to direct targeted therapy selections. A recent Canadian study (CANTRK study) comparing the detection of NTRK gene fusions on different NGS assays to determine subjects' eligibility for tyrosine kinase TRK inhibitor therapy identified the need for recommendations for best practices for laboratory testing to optimize RNA-based NGS gene fusion detection. To develop consensus recommendations, representatives from 17 Canadian genetic laboratories participated in working group discussions and the completion of survey questions about RNA-based NGS. Consensus recommendations are presented for pre-analytic, analytic and reporting aspects of gene fusion detection by RNA-based NGS.

A Two-Step Diagnostic Approach for NTRK Gene Fusion Detection in Biliary Tract and Pancreatic Adenocarcinomas.

It is of interest to determine the incidence and molecular characteristics of NTRK gene fusions in patients with bilio-pancreatic cancers, because of possible treatment with TRK inhibitors for advanced tumors. The aim of the present study was to apply the guidelines for NTRK testing algorithm to a series of patients with bilio-pancreatic cancers. Immunohistochemistry screening was applied on formalin-fixed paraffin-embedded archival blocks from surgical resections, biopsies, or cytological samples of biliary tract and pancreatic adenocarcinomas. The presence of at least a weak staining in rare tumor cells led to testing by 2 RNA-based NGS panels. For biliary tract tumors, 153 samples have been selected. A total of 140 samples were suitable to perform IHC, and 17 samples were IHC positive. RNA NGS testing of the 17 IHC-positive samples revealed a single NTRK3 gene fusion (ETV6(4)-NTRK3(14)) that was detected by both NGS panels. In this perihilar cholangiocarcinoma, IHC performed on a biopsy showed a weak focal cytoplasmic and nuclear staining. No other NTRK fusion was detected on the 16 other samples with both panels. Overall in the patients screened by IHC and confirmed by NGS, the percentage of NTRK fusions was 0.7%. For pancreatic cancers, 319 samples have been selected and 297 were suitable to perform IHC. Nineteen samples were IHC positive. No fusion was detected by NGS. NTRK gene fusions are rare in bilio-pancreatic cancers but testing is of high interest due to possible treatment with specific TRK inhibitors.