ALK Fusion Research Articles

Usefulness of an RNA extraction-free test for the multiplexed detection of ALK, ROS1, and RET Gene Fusions in Real Life FFPE Specimens of Non-Small Cell Lung Cancers

ABSTRACT Background ALK, ROS1 and RET rearrangements occur, respectively, in 5%, 2%, and 1% non-small cell lung cancers (NSCLC). ALK and ROS1 fusion proteins detection by immunohistochemistry (IHC) has been validated for rapid patient screening, but ROS1 fusions need to be confirmed by another technique and no RET IHC test is available for clinical use. Research design and methods We report herein the usefulness of the HTG EdgeSeq Assay, an RNA extraction-free test combining a quantitative nuclease protection assay with NGS, for the detection of ALK, ROS1 and RET fusions from ‘real-life’ small NSCLC samples. A total of 203 FFPE samples were collected from 11 centers. They included 143 rearranged NSCLC (87 ALK, 39 ROS1, 17 RET) and 60 ALK-ROS1-RET negative controls. Results The assay had a specificity of 98% and a sensitivity for ALK, ROS1 and RET fusions of 80%, 94% and 100% respectively. Among the 19 HTG-assay false negative samples, the preanalytical conditions were identified as the major factors impacting the assay efficiency. Conclusions Overall, the HTG EdgeSeq assay offers comparable sensitivities and specificity than other RNA sequencing techniques, with the advantage that it can be used on very small and old samples collected multicentrically.

EP08.02-40 Management of Inoperable Locally Advanced Stage III ALK fusion Positive NSCLC: A Retrospective Multi-institutional Analysis

EP08.02-40 Management of Inoperable Locally Advanced Stage III ALK fusion Positive NSCLC: A Retrospective Multi-institutional Analysis

THU223 Molecular Makeup Of Differentiated Thyroid Carcinoma In A Free-standing Children’s Hospital With A Predominantly Hispanic Population

Abstract Disclosure: A. Martinez: None. D. Baboun: None. N. Solano: None. R. Restrepo: None. C. Brathwaite: None. F. Alkhoury: None. A. Carrillo-Iregui: None. Background: Molecular testing has been incorporated into the clinical management of thyroid nodules in adults. The prevalence of oncogenic mutations and the role of molecular testing in the evaluation of thyroid nodules in children and adolescents have yet to be established. Objective: The purpose of this study is to identify the molecular makeup of thyroid nodules in patients diagnosed with differentiated thyroid carcinoma (DTC) at a free-standing children’s hospital with a predominantly Hispanic population. Methods: Upon Institutional Review Board approval, we reviewed the charts of all patients with a final diagnosis of DTC between 2012 and 2022. We analyzed demographics, histopathological diagnoses, and molecular oncogenic markers of pathology specimens when available. Statistical analysis was performed using Welch’s t-test and Fisher’s exact test. Results: Fifty-five patients between 8-20 years of age were diagnosed with DTC. Forty-nine (89.1%) patients identified as Hispanic, and 41 (74.6%) were females. Fifty-two (94.5%) patients had papillary thyroid carcinoma, and 3 (5.5%) had follicular thyroid carcinoma. Molecular testing was performed on 33 patients, of which 30 were positive for mutations and 3 undetected. BRAF V600E (43.3%) and RET/PTC (23.3%) were the most prevalent mutations detected. The average ages of patients with BRAF V600E and RET/PTC were 15.5 and 13.3 years, respectively with no statistical significance (p=.22). The average tumor sizes of patients with BRAF V600E and RET/PTC were 1.82 ± 0.95 cm and 2.5 ± 1.21 cm, respectively with no statistical significance (p=.12). Of the patients with BRAF V600E, 53.9% had lymph node involvement and none had metastasis. Of the patients with RET/PTC, 42.9% had lymph node involvement and 14.3% had metastasis. When comparing BRAFV600E and RET/PTC, there was no statistical difference with respect to lymph node involvement or metastasis (p=1.0 and p=.35, respectively). Other mutations detected include PAX8-PPARg (10.0%), ALK fusion (6.7%), RAS (3.3%), PTEN (3.3%), compound KIT and TSHR (3.3%), TRIM27-RET (3.3%), and other (3.3%). Notably, one patient presented with TRIM27-RET, which was associated with total lobe involvement, lymph node involvement, and distal metastasis. Conclusions: BRAF V600E and RET/PTC were the most prevalent molecular markers correlated with DTC in our predominantly Hispanic cohort. In comparison to BRAF V600E, RET/PTC was more prevalent in younger patients and was associated with a greater tumor size. We did not find any statistically significant differences with respect to age, tumor size, lymph node involvement, or metastasis between the aforementioned molecular markers. Incorporating molecular testing to supplement malignancy evaluation may improve clinical and surgical management for pediatric patients with DTC. Presentation: Thursday, June 15, 2023

A rapid, multiplex digital PCR assay to detect gene variants and fusions in non-small cell lung cancer.

Digital PCR (dPCR) is emerging as an ideal platform for the detection and tracking of genomic variants in cancer due to its high sensitivity and simple workflow. The growing number of clinically actionable cancer biomarkers creates a need for fast, accessible methods that allow for dense information content and high accuracy. Here, we describe a proof-of-concept amplitude modulation-based multiplex dPCR assay capable of detecting 12 single-nucleotide and insertion/deletion (indel) variants in EGFR, KRAS, BRAF, and ERBB2, 14 gene fusions in ALK, RET, ROS1 and NTRK1, and MET exon 14 skipping present in non-small cell lung cancer (NSCLC). We also demonstrate the use of multi-spectral target-signal encoding to improve the specificity of variant detection by reducing background noise by up to an order of magnitude. The assay reported an overall 100% positive percent agreement (PPA) and 98.5% negative percent agreement (NPA) compared to a sequencing-based assay in a cohort of 62 human formalin-fixed paraffin-embedded (FFPE) samples. In addition, the dPCR assay rescued actionable information in ten samples that failed to sequence, highlighting the utility of a multiplexed digital PCR assay as a potential reflex solution for challenging NSCLC samples.

182P ALK fusion detection by RNA next-generation sequencing (NGS) compared to DNA in a large, real-world non-small cell lung cancer (NSCLC) dataset

182P ALK fusion detection by RNA next-generation sequencing (NGS) compared to DNA in a large, real-world non-small cell lung cancer (NSCLC) dataset

Detection of clinically actionable gene fusions by next-generation sequencing-based RNA sequencing of non-small cell lung cancer cytology specimens: A single-center experience with comparison to fluorescence insitu hybridization.

Genomic profiling is needed to identify actionable alterations in non-small cell lung cancer (NSCLC). Panel-based testing such as next-generation sequencing (NGS) is often preferred to interrogate multiple alterations simultaneously. In this study, we evaluate the utility of an RNA-based NGS assay to detect genomic alterations in NSCLC cytology specimens and compare these results to fluorescence in situ hybridization (FISH) testing. A retrospective review was performed of 264 NSCLC cytology specimens that were concurrently tested for gene fusions by RNA-based NGS and ALK, RET, and/or ROS1 by FISH. Genomic alterations were detected in 29 cases by NGS, including ALK, RET, ROS1, NTRK, NUTM1, and FGFR3 fusions and MET exon 14 skipping alterations. Of the 20 cases with ALK, RET, and ROS1 fusions detected by NGS, 16 (80%) were concordant with the corresponding FISH results. Three cases showed discordance, where EML4::ALK (n=2) and SLC34A2::ROS1 (n=1) fusions were not detected by the corresponding FISH assay; one case with EZR::ROS1 was inadequate for FISH. No gene fusions were detected in 181 cases by NGS and 54 cases failed testing. The concordance rates for detecting ALK, RET, and ROS1 fusions using NGS and FISH were 97%, 100%, and 99.5%, respectively. RNA-based NGS can be used to detect gene fusions in NSCLC cytology cases with high concordance with FISH results. However, RNA-based NGS may have high failure rates and therefore a low threshold for reflexing inadequate cases to an orthogonal testing method is essential for comprehensive genomic profiling.

MIG6 Mediates Adaptive and Acquired Resistance to ALK/ROS1 Fusion Kinase Inhibition through EGFR Bypass Signaling.

Despite the initial benefit from tyrosine kinase inhibitors (TKI) targeting oncogenic ALK and ROS1 gene fusions in non-small cell lung cancer, complete responses are rare and resistance ultimately emerges from residual tumor cells. Although several acquired resistance mechanisms have been reported at the time of disease progression, adaptative resistance mechanisms that contribute to residual diseases before the outgrowth of tumor cells with acquired resistance are less clear. For the patients who have progressed after TKI treatments, but do not demonstrate ALK/ROS1 kinase mutations, there is a lack of biomarkers to guide effective treatments. Herein, we found that phosphorylation of MIG6, encoded by the ERRFI1 gene, was downregulated by ALK/ROS1 inhibitors as were mRNA levels, thus potentiating EGFR activity to support cell survival as an adaptive resistance mechanism. MIG6 downregulation was sustained following chronic exposure to ALK/ROS1 inhibitors to support the establishment of acquired resistance. A higher ratio of EGFR to MIG6 expression was found in ALK TKI-treated and ALK TKI-resistant tumors and correlated with the poor responsiveness to ALK/ROS1 inhibition in patient-derived cell lines. Furthermore, we identified and validated a MIG6 EGFR-binding domain truncation mutation in mediating resistance to ROS1 inhibitors but sensitivity to EGFR inhibitors. A MIG6 deletion was also found in a patient after progressing to ROS1 inhibition. Collectively, this study identifies MIG6 as a novel regulator for EGFR-mediated adaptive and acquired resistance to ALK/ROS1 inhibitors and suggests EGFR to MIG6 ratios and MIG6-damaging alterations as biomarkers to predict responsiveness to ALK/ROS1 and EGFR inhibitors.

Chinese expert consensus on immunotherapy for advanced non-small lung cancer with oncogenic driver mutations (2023 edition)

Non-small cell lung cancer (NSCLC) with oncogenic driver mutations was previously deemed " forbidden territory" for immunotherapy. With the growing understanding of the impact of target drugs on the immune microenvironment and the continuous generation of clinical evidence, immunotherapy is expected to bring new hope for the NSCLC with oncogenic driver mutations. This consensus is updated based on the Chinese expert consensus on immunotherapy for advanced non-small lung cancer with oncogenic driver mutations (2022 edition), and developed by the consensus expert panel through symposiums, combining the latest medical evidence and clinical practice. After thorough discussion, the expert panel reached new consensuses on 3 clinical questions: in patients with ALK fusion who are progressing on tyrosine kinase inhibitor(TKI) therapy, immune checkpoint inhibitors (ICIs)-based treatment is not recommended; ICIs-based treatment is recommended for patients with HER-2 mutations; ICIs-based treatment is recommended for NSCLC patients with MET exon 14 skipping after resistance to the targeted therapy. At the same time, with the continuous accumulation of clinical evidence, the recommendation levels of the three consensus opinions were adjusted in this update: the recommendation of ICIs combined with anti-angiogenesis therapy for patients with extensive progression after EGFR-TKIs resistance was adjusted to the level of strong; the ICIs recommendations for patients with advanced KRAS mutant and BRAF mutant NSCLC were adjusted to the level of consistent and strong, respectively. This updated consensus, combined with the latest evidence and clinical experience widely recognized by the expert panel in the immunotherapy of driver gene mutation advanced NSCLC, aims to provide standardized guidance for the clinical practice in China.

Frequent nuclear β-catenin expression in pulmonary enteric-type adenocarcinoma according to the current World Health Organization criteria.

Based on the current World Health Organization classification criteria, five of 3895 consecutive cases of surgically resected primary lung carcinomas (0.13%) categorized as enteric-type were analyzed. Three cases completely comprised tumor cells that resemble colorectal adenocarcinoma, while the other two cases exhibited features of conventional adenocarcinomas admixed with enteric components. Immunohistochemically, all patients expressed at least three of the five intestinal markers: CDX2, CK20, HNF4α, MUC2, and SATB2. None of the patients expressed TTF-1 and NKX3.1. Three cases showed nuclear accumulation of β-catenin, indicating activation of the Wnt/β-catenin signaling pathway; APC mutations were detected in one of these cases. TP53 mutations were detected in three cases. Mutated EGFR or ALK fusions were not detected. Our study demonstrates that pulmonary enteric-type adenocarcinomas share immunohistochemical features and genetic alterations with colorectal adenocarcinomas, which are characterized by frequent activation of the Wnt/β-catenin signaling pathway and a lack of actionable mutations.

ALK, ROS1, RET and NTRK1-3 Gene Fusions in Colorectal and Non-Colorectal Microsatellite-Unstable Cancers.

This study aimed to conduct a comprehensive analysis of actionable gene rearrangements in tumors with microsatellite instability (MSI). The detection of translocations involved tests for 5'/3'-end expression imbalance, variant-specific PCR and RNA-based next generation sequencing (NGS). Gene fusions were detected in 58/471 (12.3%) colorectal carcinomas (CRCs), 4/69 (5.8%) gastric cancers (GCs) and 3/65 (4.6%) endometrial cancers (ECs) (ALK: 8; RET: 12; NTRK1: 24; NTRK2: 2; NTRK3: 19), while none of these alterations were observed in five cervical carcinomas (CCs), four pancreatic cancers (PanCs), three cholangiocarcinomas (ChCs) and two ovarian cancers (OCs). The highest frequency of gene rearrangements was seen in KRAS/NRAS/BRAF wild-type colorectal carcinomas (53/204 (26%)). Surprisingly, as many as 5/267 (1.9%) KRAS/NRAS/BRAF-mutated CRCs also carried tyrosine kinase fusions. Droplet digital PCR (ddPCR) analysis of the fraction of KRAS/NRAS/BRAF mutated gene copies in kinase-rearranged tumors indicated that there was simultaneous co-occurrence of two activating events in cancer cells, but not genetic mosaicism. CRC patients aged above 50 years had a strikingly higher frequency of translocations as compared to younger subjects (56/365 (15.3%) vs. 2/106 (1.9%), p = 0.002), and this difference was particularly pronounced for tumors with normal KRAS/NRAS/BRAF status (52/150 (34.7%) vs. 1/54 (1.9%), p = 0.001). There were no instances of MSI in 56 non-colorectal tumors carrying ALK, ROS1, RET or NTRK1 rearrangements. An analysis of tyrosine kinase gene translocations is particularly feasible in KRAS/NRAS/BRAF wild-type microsatellite-unstable CRCs, although other categories of tumors with MSI also demonstrate moderate occurrence of these events.

Molecular analysis with pancreaseq® in evaluation and management of pancreatic cysts: A cohort of 28 patients.

Herein, we present the PancreaSeq® results of 28 patients and emphasize the usefulness of molecular testing in evaluation of pancreatic cysts. A total of 10 (35.7%) non-diagnostic, 6 (21.4%) negative, 5 (17.8%) atypical, and 7 (25%) were positive for mucinous cystic neoplasm (MCN) pancreatic cyst aspirates were analyzed with PancreaSeq® at Mayo Clinic, Jacksonville between September 2021 and February 2023. Three non-diagnostic, two negative, three atypical, and two positive for MCN cysts were positive for KRAS and GNAS mutations. They were interpreted as intraductal papillary mucinous neoplasm (IPMN) with low risk for progression to high-grade dysplasia/adenocarcinoma. One negative case was positive for KRAS and GNAS mutation and RNF43 copy number alteration. It was interpreted as IPMN with a low risk of progression. Two non-diagnostic, one negative, and two positive for MCN cysts were positive for KRAS mutation. All were interpreted as IPMN/MCNs with low risk of progression. One positive for MCN case was positive for GNAS mutation and ALK fusion and one positive for MCN case was positive for GNAS mutation, ALK fusion, and RNF43 copy number alteration. Both were interpreted as IPMN and their risk of progression was interpreted as not well understood. One atypical case was positive for KRAS and TP53 mutation and was interpreted as IPMN/ MCNs with a high risk of progression. VHL mutation was present in one non-diagnostic case. It was interpreted as serous cystadenoma and the risk for progression was low. Molecular analysis of pancreatic cysts with PancreaSeq® is useful in accurate diagnosis, especially when cytologic material is non-diagnostic and helps improve patient management.

Patterns of Treatment Failure After Selective Rearranged During Transfection (RET) Inhibitors in Patients With Metastatic Medullary Thyroid Carcinoma.

Medullary thyroid cancer (MTC) harbors frequent mutations in RET oncogene. Selective RET inhibitors (RETi) have emerged as effective treatments. However, resistance almost invariably occurs. MTC patients who were initiated on RETi between 2018 and 2022 were included. Baseline characteristics, RET mutational status, RETi response, available tumor tissue and molecular profiles sampled pre- and post-RETi were analyzed. Among 46 MTC patients on RETi during the study period, 26 patients had discontinued at data cut-off because of progression (n = 16), death (n = 4), and toxicity (n = 6). The most frequent RET mutations at baseline were p.M918T (n = 29), and p.C634X (n = 6). Pre- and post-RETi molecular profiles were available in 14 patients. There was no primary resistance on pre-RETi samples. Post-RETi profiles revealed a bypass mechanism of resistance in 75% of the cases including RAS genes mutations (50%), FGFR2 and ALK fusions and and MYC p.P44L. RET solvent from and hinge region mutations was the only resistance mechanisms in 25% of the cases. Tumor samples from initial thyroidectomy, pre- and post-RETi, from six patients, showed an increase of the mean Ki 67-index of 7%, 17% and 40% respectively (P = 0.037) and a more aggressive poorly differentiated histology in three patients. Bypass resistance may be the most frequent mechanism of progression under RETi. A more aggressive histology may arise following RETi and warrants further investigation.

Upfront liquid next-generation sequencing in treatment-naïve advanced non-small cell lung cancer patients: A prospective randomised study in the Taiwanese health system

BackgroundNext-generation sequencing (NGS) of plasma cell-free DNA identifies driver mutations in advanced non-small cell lung cancer (NSCLC) and may complement routine molecular evaluation. The utility of liquid NGS at the start of tumour workup is undetermined. MethodsThis is a randomised study of patients with suspected advanced NSCLC. All patients received blood liquid NGS testing at their first clinic visit and underwent standard histological diagnosis and tissue genotyping, encompassing polymerase chain reaction based methods for EGFR mutation, immunohistochemical (IHC) staining for ALK fusion and BRAF V600E mutation, and an IHC screening followed by confirmation using fluorescence in situ hybridization confirmation for ROS1 fusion. They were then randomly assigned to receive NGS results either after tissue genotyping (Group A) or as soon as possible after histological diagnosis of advanced NSCLC (Group B). The study measured time to start of systemic treatment as the primary endpoint and secondary endpoints included biomarker discovery rate, objective response rate (ORR), and progression-free survival (PFS). ResultsThis study enroled 180 patients with suspected advanced NSCLC, randomised into two groups. 63 patients in Group A and 59 in Group B with advanced NSCLC were confirmed as advanced NSCLC and analysed. Most had adenocarcinoma (Group A: 77.8%, Group B: 79.7%). The prevalence of EGFR mutations in the two groups was similar (Group A: 57.1%; Group B: 56.6%). Other driver alterations were rare. The median time to treatment was shorter in Group B (20 days) than in Group A (28 days). ORR and PFS did not differ between groups significantly. Liquid NGS had high concordance with tissue testing and identified driver mutations in 42.6% (20/47) of tissue-negative cases. ConclusionPerforming liquid NGS at the initial clinic visit for suspected advanced NSCLC identifies more patients suitable for targeted therapies and shortens time to the start of treatment.

NTRK expression is common in xanthogranuloma and is associated with the solitary variant.

Previously identified mutually-exclusive driver genes in juvenile xanthogranuloma (JXG) and adult xanthogranuloma (AXG) include mutations in MAP kinase pathway genes such as MAP2K1, BRAF, ARAF, KRAS, NRAS, PIK3CD as well as fusions in BRAF and ALK, with a subset of cases with no identified driver yet. NTRK fusion has been identified in rare cases. We identified two consecutive index cases of localized JXG or AXG with NTRK1 fusion by next-generation sequencing (NGS) and confirmed by pan-NTRK immunostain. We expanded the study to a total of 50 cases of JXG and AXG using screening by pan-NTRK immunostain. We confirmed the specificity of our approach with negative results in 5 cases of histiocytic neoplasia lacking an NTRK fusion by NGS and 14 cases of non-neoplastic histiocytic disease. We found 23 cases of JXG or AXG with overexpression of NTRK by immunostain, and these cases were restricted to localized disease (23 of 43 cases, 53.5%) rather than disseminated disease (zero of seven cases). NTRK expression is common in JXG or AXG and associated with localized rather than disseminated disease. We speculate that the potential importance of this in JXG and AXG has not been previously appreciated due to the tendency to focus sequencing studies on disseminated disease. We confirm the presence of an NTRK1 fusion in two positive cases by NGS, however, additional genetic studies are necessary to further explore this.

Brigatinib Versus Alectinib in ALK-Positive NSCLC After Disease Progression on Crizotinib: Results of Phase 3 ALTA-3 Trial

IntroductionThis open-label, phase 3 trial (ALTA-3; NCT03596866) compared efficacy and safety of brigatinib versus alectinib for ALK+ NSCLC after disease progression on crizotinib. MethodsPatients with advanced ALK+ NSCLC that progressed on crizotinib were randomized 1:1 to brigatinib 180 mg once daily (7-d lead-in, 90 mg) or alectinib 600 mg twice daily, aiming to test superiority. The primary end point was blinded independent review committee–assessed progression-free survival (PFS). Interim analysis for efficacy and futility was planned at approximately 70% of 164 expected PFS events. ResultsThe population (N = 248; brigatinib, n = 125; alectinib, n = 123) was notable for long median duration of prior crizotinib (16.0–16.8 mo) and low rate of ALK fusion in baseline circulating tumor DNA (ctDNA; 78 of 232 [34%]). Median blinded independent review committee–assessed PFS was 19.3 months with brigatinib and 19.2 months with alectinib (hazard ratio = 0.97 [95% confidence interval: 0.66–1.42], p = 0.8672]). The study met futility criterion. Overall survival was immature (41 events [17%]). Exploratory analyses pooled across the treatment groups revealed median PFS of 11.1 versus 22.5 months in patients with versus without ctDNA-detectable ALK fusion at baseline (hazard ratio: 0.48 [95% confidence interval: 0.32–0.71]). Treatment-related adverse events in more than 30% of patients (brigatinib, alectinib) were elevated levels of blood creatine phosphokinase (70%, 29%), aspartate aminotransferase (53%, 38%), and alanine aminotransferase (40%, 36%). ConclusionsBrigatinib was not superior to alectinib for PFS in crizotinib-pretreated ALK+ NSCLC. Safety was consistent with the well-established and unique profiles of each drug. The low proportion of patients with ctDNA-detectable ALK fusion may account for prolonged PFS with both drugs in ALTA-3.

Spotlight on Cemiplimab-rwlc in the Treatment of Non-Small Cell Lung Cancer (NSCLC): Focus on Patient Selection and Considerations.

In metastatic non-small cell lung cancer (NSCLC), tumors that do not harbor driver mutations in EGFR or gene fusions in ALK and ROS, PD-1 and PD-L1 inhibitors have become a cornerstone in first line treatment, either as monotherapy or in combination with chemotherapy. This paper reviews cemiplimab-rwlc, the third PD-1/L1 inhibitor to be approved in the setting for first line treatment in NSCLC, as monotherapy or in combination therapy with chemotherapy, to provide a perspective on the subtle differences in patient population for the cemiplimab studies and consideration of its primary and subgroup results in the context of first line therapies for NSCLC.

EML4::ALK fusions in complex lymphatic malformations.

Gorham-Stout disease (GSD) and generalized lymphatic anomaly (GLA) are subtypes of complex lymphatic malformations (CLMs) with osseous involvement that cause significant complications, including pain and pathologic fractures. As with other vascular anomalies, somatic mosaic mutations in oncogenes are often present, and the mTOR inhibitor sirolimus alleviates symptoms in some, but not all, patients. We describe two patients, one with GSD and one with GLA, found to have EML4::ALK fusions. This report of a targetable, oncogenic fusion in vascular malformations expands our understanding of the genetic basis for CLMs and suggests additional targeted therapies could be effective.

Interim survival analysis of the randomized phase III GEMSTONE-302 trial: sugemalimab or placebo plus chemotherapy as first-line treatment for metastatic NSCLC.

The randomized, double-blinded, multi-center, phase III GEMSTONE-302 ( NCT03789604 ) study evaluated the efficacy and safety of sugemalimab versus placebo in combination with chemotherapy as first-line treatment for metastatic non-small-cell lung cancer (NSCLC). In this study, 479 treatment-naive patients with stage IV squamous or non-squamous NSCLC without known EGFR sensitizing mutations, ALK, ROS1 or RET fusions were randomized (2:1) to receive 1,200 mg of sugemalimab (n = 320) or placebo (n = 159) every 3 weeks in combination with platinum-based chemotherapy for up to four cycles, followed by maintenance therapy with sugemalimab or placebo for squamous NSCLC and sugemalimab or placebo plus pemetrexed for non-squamous NSCLC. Placebo-treated patients could cross over to receive sugemalimab monotherapy on disease progression. The primary endpoint was investigator-assessed progression-free survival (PFS) and the secondary endpoints included overall survival (OS) and objective response rate. Sugemalimab plus chemotherapy has demonstrated significant PFS prolongation in the primary analysis as reported previously. As of 22 November 2021, the prespecified interim OS analysis showed significant improvement with the addition of sugemalimab to chemotherapy (median OS = 25.4 versus 16.9 months; hazard ratio = 0.65; 95% confidence interval = 0.50-0.84; P = 0.0008). Sugemalimab plus chemotherapy provided superior PFS and OS compared to placebo plus chemotherapy, supporting the use of sugemalimab as a first-line treatment option for metastatic NSCLC.

HGG-04. INFANTILE HIGH GRADE GLIOMA: HONG KONG EXPERIENCE

Abstract OBJECTIVE To review local infantile high-grade glioma (IHG) patients and their outcome. BACKGROUND Infantile high-grade glioma is diagnosed in patients less than 12 months of age. Studies have shown that it displays a more stable genome, and are usually single mutation driven. The most identifiable mutations are receptor tyrosine kinase (RTK) fusion, such as NTRK family, ROS1, ALK and MET. The current principal treatment remains to be surgery, but it is challenging for a complete resection due to hemispheric involvement. Chemotherapeutic drugs for IHG are still under debate, with targeted therapy showing efficacy in promoting tumour shrinkage. Despite being a challenging CNS tumour, the overall survival of IHG is superior to other paediatric high-grade gliomas. Result: We identified 7 IHG patients in our local data. Mean age of diagnosis was 3 months. There were 4 males and 3 females. Six patients had histological diagnosis of glioblastoma and 1 patient had diagnosis of anaplastic astrocytoma. One patient had her tumour located in infratentorial region. Three patients had multilobar involvement. NTRK fusion was found in 4 patients (NTRK fusion, ETV6-NTRK3 fusion and TPR-NTRK1 fusion). ALK fusion was found in 1 patient (HMBOX1-ALK). All patients underwent chemotherapy, with four patients switched to NTRK inhibitor afterwards. Surgery was performed at various time points for these patients. One patient passed away at 22 months of age at submission of this abstract. CONCLUSION A local review gives us more insight into the updated diagnosis, management and outcome of infantile patients diagnosed with high-grade glioma. Infantile high-grade glioma should be regarded as a unique tumour entity and a multidisciplinary approach is paramount in improving survival for this group of patients.

A Shift in Molecular Drivers of Papillary Thyroid Carcinoma Following the 2017 World Health Organization Classification: Characterization of 554 Consecutive Tumors With Emphasis on BRAF-Negative Cases

Most studies for comprehensive molecular profiling of papillary thyroid carcinoma (PTC) have been performed before the 2017 World Health Organization (WHO) classification, in which the diagnostic criteria of follicular variants of PTC have been modified and noninvasive follicular thyroid neoplasm with papillary-like nuclear features has been introduced. This study aims to investigate the shift in the incidence of BRAF V600E mutations in PTCs following the 2017 WHO classification and to further characterize the histologic subtypes and molecular drivers in BRAF-negative cases. The study cohort consisted of 554 consecutive PTCs larger than 0.5 cm between January 2019 and May 2022. Immunohistochemistry for BRAF VE1 was performed for all cases. Compared with a historical cohort of 509 PTCs from November 2013 to April 2018, the incidence of BRAF V600E mutations was significantly higher in the study cohort (86.8% vs 78.8%, P = .0006). Targeted RNA-based next-generation sequencing using a FusionPlex Pan Solid Tumor v2 panel (ArcherDX) was performed for BRAF-negative PTCs from the study cohort. Eight cribriform-morular thyroid carcinomas and 3 cases with suboptimal RNA quality were excluded from next-generation sequencing. A total of 62 BRAF-negative PTCs were successfully sequenced, including 19 classic follicular predominant PTCs, 16 classic PTCs, 14 infiltrative follicular PTCs, 7 encapsulated follicular PTCs, 3 diffuse sclerosing PTCs, 1 tall cell PTC, 1 solid PTC, and 1 diffuse follicular PTC. Among them, RET fusions were identified in 25 cases, NTRK3 fusions in 13 cases, BRAF fusions in 5 cases including a novel TNS1::BRAF fusion, NRAS Q61R mutations in 3 cases, KRAS Q61K mutations in 2 cases, NTRK1 fusions in 2 cases, an ALK fusion in 1 case, an FGFR1 fusion in 1 case, and an HRAS Q61R mutation in 1 case. No genetic variants, from our commercially employed assay, were detected in the remaining 9 cases. In summary, the incidence of BRAF V600E mutations in PTCs significantly increased from 78.8% to 86.8% in our post–2017 WHO classification cohort. RAS mutations accounted for only 1.1% of the cases. Driver gene fusions were identified in 8.5% of PTCs and were clinically relevant given the emerging targeted kinase inhibitor therapy. Of the 1.6% of cases for which no driver alteration was detected, the specificity of drivers tested and tumor classification require further investigation.