RET Fluorescence In Situ Hybridization Analysis Is a Sensitive but Highly Unspecific Screening Method for RET Fusions in Lung Cancer

IntroductionRET gene fusions are established oncogenic drivers in 1% of NSCLC. Accurate detection of advanced patients with RET fusions is essential to ensure optimal therapy choice. We investigated the performance of fluorescence in situ hybridization (FISH) as a diagnostic test for detecting functional RET fusions.MethodsBetween January 2016 and November 2019, a total of 4873 patients with NSCLC were routinely screened for RET fusions using either FISH (n = 2858) or targeted RNA next-generation sequencing (NGS) (n = 2015). If sufficient material was available, positive cases were analyzed by both methods (n = 39) and multiple FISH assays (n = 17). In an independent cohort of 520 patients with NSCLC, whole-genome sequencing data were investigated for disruptive structural variations and functional fusions in the RET and compared with ALK and ROS1 loci.ResultsFISH analysis revealed RET rearrangement in 48 of 2858 cases; of 30 rearranged cases double tested with NGS, only nine had a functional RET fusion. RNA NGS yielded RET fusions in 14 of 2015 cases; all nine cases double tested by FISH had RET locus rearrangement. Of these 18 verified RET fusion cases, 16 had a split signal and two a complex rearrangement by FISH. By whole-genome sequencing, the prevalence of functional fusions compared with all disruptive events was lower in the RET (4 of 9, 44%) than the ALK (27 of 34, 79%) and ROS1 (9 of 12, 75%) loci.ConclusionsFISH is a sensitive but unspecific technique for RET screening, always requiring a confirmation using an orthogonal technique, owing to frequently occurring RET rearrangements not resulting in functional fusions in NSCLC.     

Identification and characterization of RET fusions in advanced colorectal cancer

There is an unmet clinical need for molecularly directed therapies available for metastatic colorectal cancer. Comprehensive genomic profiling has the potential to identify actionable genomic alterations in colorectal cancer. Through comprehensive genomic profiling we prospectively identified 6 RET fusion kinases, including two novel fusions of CCDC6-RET and NCOA4-RET, in metastatic colorectal cancer (CRC) patients. RET fusion kinases represent a novel class of oncogenic driver in CRC and occurred at a 0.2% frequency without concurrent driver mutations, including KRAS, NRAS, BRAF, PIK3CA or other fusion tyrosine kinases. Multiple RET kinase inhibitors were cytotoxic to RET fusion kinase positive cancer cells and not RET fusion kinase negative CRC cells. The presence of a RET fusion kinase may identify a subset of metastatic CRC patients with a high response rate to RET kinase inhibition. This is the first characterization of RET fusions in CRC patients and highlights the therapeutic significance of prospective comprehensive genomic profiling in advanced CRC.     

Detection of Novel NRG1, EGFR,and MET Fusions in Lung Adenocarcinomas in the Chinese Population

IntroductionMultiple oncogene fusions beyond ALK receptor tyrosine kinase (ALK), RET, and ROS1 fusion has been described in lung cancer, especially in lung adenocarcinomas without common oncogenic mutations. Molecular inhibitors have been developed and proved effective for patients whose tumors harbor these novel alterations.MethodsA consecutive series of surgically resected lung adenocarcinomas were collected and profiled using an enrichment strategy to detect nine common oncogenic driver mutations and fusions concerning EGFR, KRAS, HER2, BRAF, MET, ALK, RET, ROS1, and FGFR. Driver-negative cases were further analyzed by a comprehensive RNA-based next-generation sequencing (NGS) fusion assay for novel fusions.ResultsIn total, we profiled 1681 lung adenocarcinomas, among which 255 cases were common driver–negative. One hundred seventy-seven cases had sufficient tissue for NGS fusions screening, which identified eight novel fusions. NRG1 fusions occurred in 0.36% of all lung adenocarcinoma cases (6 of 1681 cases), including 4 CD74-NRG1–positive cases, 1 RBPMS-NRG1–positive case, and 1 novel ITGB1-NRG1–positive case. Furthermore, another 2 novel fusions were also detected, including 1 EGFR-SHC1 fusion and 1 CD47-MET fusion, both of which were in-frame and retained the functional domain of the corresponding kinases. No fusion event was detected for NTRK, KRAS, BRAF or HER2 genes in this cohort. Detailed clinicopathologic data showed that invasive mucous adenocarcinoma (three of eight cases) and acinar-predominant adenocarcinoma (three of eight cases) were the most prevalent pathologic subtypes among novel fusions.ConclusionsFusions affecting NRG1, EGFR, and MET were detected in 0.48% of unselected lung adenocarcinomas, and NRG1 fusions ranked the most prevalent fusions in common driver-negative lung adenocarcinomas from Chinese population. RNA-based NGS fusion assay was an optional method for screening actionable fusions in common driver-negative cases.     

Combinational Analysis of FISH and Immunohistochemistry Reveals Rare Genomic Events in ALK Fusion Patterns in NSCLC that Responds to Crizotinib Treatment

IntroductionThe purpose of this study was to explore the complicated rearrangement mechanisms underlying cases with atypical and negative anaplastic lymphoma receptor tyrosine kinase gene (ALK) fluorescence hybridization (FISH) and positive immunohistochemistry (IHC) results and to stress the importance of combinational assay of these two methods in current pathological diagnosis.MethodsA total of 3128 NSCLCs were screened for ALK fusions through both FISH analysis and IHC assays with Ventana-D5F3 antibody. Fourteen cases with atypical and negative FISH results with the current criteria and positive IHC results were analyzed with targeted next-generation sequencing (NGS).ResultsOf the 3128 cases tested, 228 (7.3%) and 214 (6.8%) were ALK positive by IHC and FISH, respectively. Fourteen cases with negative and atypical FISH results all demonstrated IHC positivity. Of 2991 cases, eight (0.27%) with negative FISH results demonstrated echinoderm microtubule associated protein like 4 gene (EML4)-ALK fusions revealed by targeted NGS, and the relative abundance of fusion ranged from 0.9% to 46.8%. Three of 2991 cases (0.1%) did not exhibit any type of ALK fusions. In addition, two patients showed an isolated 5′ side signal and targeted NGS revealed two novel ALK partner genes, baculoviral IAP repeat containing 6 gene (BIRC6) and phosphatidylinositol binding clathrin assembly protein gene (PICALM). One patient showed an isolated and attenuated 3′ red signal and demonstrated a novel translocation partner with CCAAT/enhancer binding protein zeta gene (CEBPZ). Of all the patients, four received crizotinib treatment and demonstrated partial responses at the end of follow-up.ConclusionsOur study showed that patients with negative and atypical ALK FISH patterns may have positive results for IHC testing and harbor the translocation partners of EML4 or other genes. Therefore, additional testing with NGS should be conducted to explore the molecular mechanisms underlying the complicated gene rearrangement events.     

Optimizing Mutation and Fusion Detection in NSCLC by Sequential DNA and RNA Sequencing

IntroductionFrequently, patients with locally advanced or metastatic NSCLC are screened for mutations and fusions. In most laboratories, molecular workup includes a multitude of tests: immunohistochemistry (ALK, ROS1, and programmed death-ligand 1 testing), DNA sequencing, in situ hybridization for fusion, and amplification detection. With the fast-emerging new drugs targeting specific fusions and exon-skipping events, this procedure harbors a growing risk of tissue exhaustion.MethodsIn this study, we evaluated the benefit of anchored, multiplexed, polymerase chain reaction-based targeted RNA sequencing (RNA next-generation sequencing [NGS]) in the identification of gene fusions and exon-skipping events in patients, in which no pathogenic driver mutation was found by DNA-based targeted cancer hotspot NGS (DNA NGS). We analyzed a cohort of stage IV NSCLC cases from both in-house and referral hospitals, consisting 38.5% cytology samples and 61.5% microdissected histology samples, mostly core needle biopsies. We compared molecular findings in a parallel workup (DNA NGS and RNA NGS, cohort 1, n = 198) with a sequential workup (DNA NGS followed by RNA NGS in selected cases, cohort 2, n = 192). We hypothesized the sequential workup to be the more efficient procedure.ResultsIn both cohorts, a maximum of one oncogenic driver mutation was found per case. This is in concordance with large, whole-genome databases and suggests that it is safe to omit RNA NGS when a clear oncogenic driver is identified in DNA NGS. In addition, this reduced the number of necessary RNA NGS to only 53% of all cases. The tumors of never smokers, however, were enriched for fusions and exon-skipping events (32% versus 4% in former and current smokers, p = 0.00), and therefore benefited more often from the shorter median turnaround time of the parallel approach (15 d versus only 9 d in the parallel workup).ConclusionsWe conclude that sequentially combining DNA NGS and RNA NGS is the most efficient strategy for mutation and fusion detection in smoking-associated NSCLC, whereas for never smokers we recommend a parallel approach. This approach was shown to be feasible on small tissue samples including for cytology tests, can drastically reduce the complexity and cost of molecular workup, and also provides flexibility in the constantly evolving landscape of actionable targets in NSCLC.     

Detection of Nonreciprocal/Reciprocal ALK Translocation as Poor Predictive Marker in Patients With First-Line Crizotinib-Treated ALK-Rearranged NSCLC

IntroductionDuring nonreciprocal/reciprocal translocation process, 5′-anaplastic lymphoma kinase (ALK) sometimes gets retained in the genome and is detectable by next-generation sequencing; however, no study has investigated its clinical significance. Our study aimed to assess the impact of harboring 5′-ALK on the efficacy of crizotinib.MethodsA total of 150 patients with next-generation sequencing–identified ALK-rearranged NSCLC from March 2014 to July 2018 at the Hunan Cancer Hospital were enrolled in this study. The efficacy of crizotinib as first-line therapy was evaluated in 112 patients according to the retention of 5′-ALK.ResultsAmong the 150 patients with NSCLC, nonreciprocal/reciprocal translocation was detected in 18.7% (28 of 150), and 3′-ALK fusion alone was detected in 81.3% (122 of 150). Among the 112 patients who received first-line crizotinib, 89 had 3′-ALK fusion alone (79 echinoderm microtubule associated protein-like 4 [EML4]-ALK and 10 non–EML4-ALK), and 23 had nonreciprocal/reciprocal ALK translocation. Among the patients with nonreciprocal/reciprocal ALK translocation, three patients harbored dual concurrent 3′-ALK fusions. Patients with nonreciprocal/reciprocal ALK translocation had higher incidence of brain metastasis at baseline than those with 3′-ALK fusion alone (39.1% versus 13.4%, p = 0.028). Crizotinib-treated patients with nonreciprocal/reciprocal ALK translocation had significantly shorter median progression-free survival (PFS) compared with patients carrying 3′-ALK fusion alone (6.1 m versus 12.0 m, p = 0.001) or with EML4-ALK fusion alone (6.1 m versus 12.6 m, p = 0.001). Multivariate analysis revealed that harboring nonreciprocal/reciprocal ALK translocation was an independent predictor of worse PFS for crizotinib-treated ALK-rearranged NSCLC (p = 0.0046).ConclusionsPresence of nonreciprocal/reciprocal ALK translocation was predictive for worse PFS and greater likelihood of baseline brain metastases in patients with ALK-rearranged NSCLC who received first-line crizotinib.     

Molecular Characterization and Clinical Outcomes in RET-Rearranged NSCLC

IntroductionRET rearrangements are an emerging targetable oncogenic fusion driver in NSCLC. However, the natural history of disease and activity of different classes of systemic therapy remain to be defined. Furthermore, molecular testing for RET is not yet routine, and the optimal method of testing is unclear. We present a comparative analysis of molecular profiling with fluorescence in situ hybridization (FISH) or next-generation sequencing (NGS) and treatment outcomes.MethodsThis study was a retrospective analysis of patients treated at the National Cancer Centre Singapore. Baseline demographics and treatment outcomes were collected.ResultsA total of 64 patients were included, with a median age of 62 years (range: 25–85), 56% were women, 77% were of Chinese ethnicity, 95% had adenocarcinoma, and 69% were never smokers. RET rearrangement was detected by FISH in 30 of 34 patients (88%), NGS in 40 of 43 patients (93%), and with discordant results in seven of 13 patients (54%) tested with both methods. Of 61 patients with stage IIIB/IV or recurrent disease, prevalence of central nervous system metastases was 31% and 92% received palliative systemic therapy. Overall survival was prolonged in patients treated with a selective RET tyrosine kinase inhibitor versus untreated patients (median 49.3 versus 15.3 mo; hazard ratio [HR]: 0.16, 95% confidence interval [CI]: 0.06–0.40, p < 0.001). However, it was not different in patients treated with immunotherapy versus untreated patients (median 37.7 versus 49.3 mo; HR: 1.30, 95% CI: 0.53–3.19, p = 0.53). Overall survival was also prolonged in patients with CCDC6-RET fusion versus those with KIF5B-RET fusion (median 113.5 versus 37.7 mo; HR: 0.12, 95% CI: 0.04–0.38, p = 0.009).ConclusionsIn RET-rearranged NSCLC, selective RET tyrosine kinase inhibitor therapy is associated with improved survival outcomes, especially in patients with CCDC6-RET fusion. However, immunotherapy has poor efficacy. NGS and FISH testing methods may also result in substantial discordance.     

Amplicon-based next-generation sequencing of plasma cell-free DNA for detection of driver and resistance mutations in advanced non-small cell lung cancer

BackgroundGenomic analysis of plasma cell-free DNA is transforming lung cancer care; however, available assays are limited by cost, turnaround time, and imperfect accuracy. Here, we study amplicon-based plasma next-generation sequencing (NGS), rather than hybrid-capture-based plasma NGS, hypothesizing this would allow sensitive detection and monitoring of driver and resistance mutations in advanced non-small cell lung cancer (NSCLC).Patients and methodsPlasma samples from patients with NSCLC and a known targetable genotype (EGFR, ALK/ROS1, and other rare genotypes) were collected while on therapy and analyzed blinded to tumor genotype. Plasma NGS was carried out using enhanced tagged amplicon sequencing of hotspots and coding regions from 36 genes, as well as intronic coverage for detection of ALK/ROS1 fusions. Diagnostic accuracy was compared with plasma droplet digital PCR (ddPCR) and tumor genotype.ResultsA total of 168 specimens from 46 patients were studied. Matched plasma NGS and ddPCR across 120 variants from 80 samples revealed high concordance of allelic fraction (R² = 0.95). Pretreatment, sensitivity of plasma NGS for the detection of EGFR driver mutations was 100% (30/30), compared with 87% for ddPCR (26/30). A full spectrum of rare driver oncogenic mutations could be detected including sensitive detection of ALK/ROS1 fusions (8/9 detected, 89%). Studying 25 patients positive for EGFR T790M that developed resistance to osimertinib, 15 resistance mechanisms could be detected including tertiary EGFR mutations (C797S, Q791P) and mutations or amplifications of non-EGFR genes, some of which could be detected pretreatment or months before progression.ConclusionsThis blinded analysis demonstrates the ability of amplicon-based plasma NGS to detect a full range of targetable genotypes in NSCLC, including fusion genes, with high accuracy. The ability of plasma NGS to detect a range of preexisting and acquired resistance mechanisms highlights its potential value as an alternative to single mutation digital PCR-based plasma assays for personalizing treatment of TKI resistance in lung cancer.     

Novel Targets in Non‐Small Cell Lung Cancer: ROS1 and RET Fusions

The discovery of chromosomal rearrangements involving the anaplastic lymphoma kinase (ALK) gene in non‐small cell lung cancer (NSCLC) has stimulated renewed interest in oncogenic fusions as potential therapeutic targets. Recently, genetic alterations in ROS1 and RET were identified in patients with NSCLC. Like ALK, genetic alterations in ROS1 and RET involve chromosomal rearrangements that result in the formation of chimeric fusion kinases capable of oncogenic transformation. Notably, ROS1 and RET rearrangements are rarely found with other genetic alterations, such as EGFR, KRAS, or ALK. This finding suggests that both ROS1 and RET are independent oncogenic drivers that may be viable therapeutic targets. In initial screening studies, ROS1 and RET rearrangements were identified at similar frequencies (approximately 1%–2%), using a variety of genotyping techniques. Importantly, patients with either ROS1 or RET rearrangements appear to have unique clinical and pathologic features that may facilitate identification and enrichment strategies. These features may in turn expedite enrollment in clinical trials evaluating genotype‐directed therapies in these rare patient populations. In this review, we summarize the molecular biology, clinical features, detection, and targeting of ROS1 and RET rearrangements in NSCLC.     

Clinical outcomes with pemetrexed-based systemic therapies in RET-rearranged lung cancers

BackgroundRET rearrangements are targetable, oncogenic lung cancer drivers. While previous series have shown durable clinical benefit with pemetrexed-based therapies in ALK- and ROS1-rearranged lung cancers, the benefits of pemetrexed-based treatments in patients with RET-rearranged lung cancers relative to other genomic subsets have not previously been explored.Patients and methodsA retrospective review of patients with pathologically confirmed stage IIIB/IV lung adenocarcinomas and evidence of a RET, ROS1, or ALK rearrangement, or a KRAS mutation was conducted. Patients were eligible if they received treatment with pemetrexed alone or in combination. The primary outcome of progression-free survival (PFS), and secondary outcomes of overall response rate (ORR, RECIST v1.1), time to progression (TTP), and time to treatment discontinuation were compared between RET-rearranged and groups of ROS1-rearranged, ALK-rearranged, and KRAS-mutant lung cancers.ResultsWe evaluated 104 patients. Patients with RET-rearranged lung cancers (n = 18) had a median PFS of 19 months [95% confidence interval (CI) 12–not reached (NR)] that was comparable with patients with ROS1- (23 months, 95% CI 14–NR, n = 10) and ALK-rearranged (19 months, 95% CI 15–36, n = 36) lung cancers, and significantly improved compared with patients with KRAS-mutant lung cancers (6 months, 95% CI 5–9, P < 0.001, n = 40). ORR (45%), median TTP (20 months, 95% CI 17–NR), and median time to treatment discontinuation (21 months, 95% CI 6–NR) in patients with RET-rearranged lung cancers were not significantly different compared with patients with ALK- and ROS1-rearranged lung cancers, and improved compared with patients with KRAS-mutant lung cancers.ConclusionDurable benefits with pemetrexed-based therapies in RET-rearranged lung cancers are comparable with ALK- and ROS1-rearranged lung cancers. When selecting therapies for patients with RET-rearranged lung cancers, pemetrexed-containing regimens should be considered.     

Multiplex genomic profiling of non–small cell lung cancers from the LETS phase III trial of first-line S-1/carboplatin versus paclitaxel/carboplatin: results of a West Japan Oncology Group study

Archival formalin-fixed, paraffin-embedded (FFPE) tumor specimens were collected from advanced NSCLC patients enrolled in LETS phase III trial comparing first-line S-1/carboplatin with paclitaxel/carboplatin and subjected to multiplex genotyping for 214 somatic hotspot mutations in 26 genes (LungCarta Panel) and 20 major variants of ALK, RET, and ROS1 fusion genes (LungFusion Panel) with the Sequenom MassARRAY platform. MET amplification was evaluated by fluorescence in situ hybridization. A somatic mutation in at least one gene was identified in 48% of non–squamous cell carcinoma and 45% of squamous cell carcinoma specimens, with EGFR (17%), TP53 (11%), STK11 (9.8%), MET (7.6%), and KRAS (6.2%). Mutations in EGFR or KRAS were associated with a longer or shorter median overall survival, respectively. The LungFusion Panel identified ALK fusions in six cases (2.5%), ROS1 fusions in five cases (2.1%), and a RET fusion in one case (0.4%), with these three types of rearrangement being mutually exclusive. Nine (3.9%) of 229 patients were found to be positive for de novo MET amplification. This first multiplex genotyping of NSCLC associated with a phase III trial shows that MassARRAY-based genetic testing for somatic mutations and fusion genes performs well with nucleic acid derived from FFPE specimens of NSCLC tissue.     

Benefit of Targeted DNA Sequencing in Advanced Non–Small-Cell Lung Cancer Patients Without EGFR and ALK Alterations on Conventional Tests

BackgroundGenetic sequencing testing has become widely used to inform treatment decisions for advanced non–small-cell lung cancer (NSCLC) patients. We analyzed benefits of genetic sequencing testing in real practice.Patients and MethodsWe retrospectively reviewed 209 NSCLC patients who had no EGFR and ALK alterations on routine molecular tests and underwent next-generation targeted DNA sequencing of 380 cancer-related genes between November 2013 and October 2016. Median patient age was 59 years. A total of 96 patients (46%) were never smokers, and 195 patients (93%) had adenocarcinoma.ResultsAmong 209 total patients, 64 (31%) demonstrated actionable genetic alterations; 20 had EGFR mutations (6 L858R, 8 exon 19 deletions, 1 L861Q, 1 G719S, 4 exon 20 duplications), 4 ALK fusions, 9 ROS1 fusions, 6 BRAF V600E mutations, 15 RET fusions, 1 MET high-level amplification, 6 MET exon 14 skipping mutations, and 3 ERBB2 exon 20 insertion mutations. Of the 64 patients harboring actionable alterations, 28 patients received therapy targeted to their own actionable alterations (15 EGFR, 3 ALK, 1 ROS1, 8 RET, 1 BRAF). There were significant differences in overall survival between individuals with no actionable alterations, those with actionable alterations but no targeted therapy, and those with actionable alterations and targeted therapy (20.1 vs. 17.1 vs. 66.2 months, P < .001).ConclusionThe results of targeted DNA sequencing testing could provide improved treatment options for some NSCLC patients and result in a survival benefit to NSCLC patients with no EGFR and ALK alterations on routine tests who are treated with targeted therapy.     

Quantifying the Value of Multigene Testing in Resected Early Stage Lung Adenocarcinoma

IntroductionTyrosine kinase inhibitors and immune checkpoint inhibitors (ICIs), each requiring testing for precision biomarkers, have recently been approved in the adjuvant setting. We assessed the potential value of multigene testing in early lung adenocarcinoma (LUAD).MethodsUsing a real-world clinicogenomic database linking deidentified electronic health record–derived clinical data to genomic data, we selected patients with LUAD who underwent tissue comprehensive genomic profiling (CGP). Using a probabilistic decision tree, we estimated the cost implications of the avoidance of adjuvant ICI in patients with programmed death-ligand 1–positive (PD-L1+) LUAD and an ALK, ROS1 or RET driver.ResultsThe CGP was performed on a specimen collected before advanced disease in 20% (1320 of 6697) of cases and ordered before advanced diagnosis for 12.6% (847 of 6697) of patients. The prevalence of driver alterations in early and advanced-stage specimens was similar, though KRAS mutations were enriched in early disease and drivers including ALK rearrangements in advanced disease. Patients who had CGP results obtained before versus after recurrence had less time between recurrence and the start of any first-line treatment (median 3.6 versus 6 wk, p < 0.001). Through avoidance of ICI in programmed death-ligand 1–positive early LUAD with an ALK, ROS1 or RET driver, we estimated that the universal CGP could reduce expected costs by $1597.23 per patient relative to EGFR single-gene testing.ConclusionsThe CGP can identify driver alterations and accelerate the start of first-line therapy at recurrence. It may also represent a cost-effective approach for avoiding futile adjuvant ICI in patients with drivers that have historically lacked activity with ICI in metastatic disease.