RET Fusion Research Articles

RET Fusion Testing in Patients With NSCLC: The RETING Study

IntroductionRET inhibitors with impressive overall response rates are now available for patients with NSCLC, yet the identification of RET fusions remains a difficult challenge. Most guidelines encourage the upfront use of next-generation sequencing (NGS), or alternatively, fluorescence in situ hybridization (FISH) or reverse transcriptase-polymerase chain reaction (RT-PCR) when NGS is not possible or available. Taken together, the suboptimal performance of single-analyte assays to detect RET fusions, although consistent with the notion of encouraging universal NGS, is currently widening some of the clinical practice gaps in the implementation of predictive biomarkers in patients with advanced NSCLC. MethodsThis situation prompted us to evaluate several RET assays in a large multicenter cohort of RET fusion–positive NSCLC (n = 38) to obtain real-world data. In addition to RNA-based NGS (the criterion standard method), all positive specimens underwent break-apart RET FISH with two different assays and were also tested by an RT-PCR assay. ResultsThe most common RET partners were KIF5B (78.9%), followed by CCDC6 (15.8%). The two RET NGS-positive but FISH-negative samples contained a KIF5B(15)-RET(12) fusion. The three RET fusions not identified with RT-PCR were AKAP13(35)-RET(12), KIF5B(24)-RET(9) and KIF5B(24)-RET(11). All three false-negative RT-PCR cases were FISH-positive, exhibited a typical break-apart pattern, and contained a very high number of positive tumor cells with both FISH assays. Signet ring cells, psammoma bodies, and pleomorphic features were frequently observed (in 34.2%, 39.5%, and 39.5% of tumors, respectively). ConclusionsIn-depth knowledge of the advantages and disadvantages of the different RET testing methodologies could help clinical and molecular tumor boards implement and maintain sensible algorithms for the rapid and effective detection of RET fusions in patients with NSCLC. The likelihood of RET false-negative results with both FISH and RT-PCR reinforces the need for upfront NGS in patients with NSCLC.

Systemic therapies for advanced thyroid cancer - an update

Based on phase III clinical studies, four multi-kinase inhibitors (MKI) are approved for the treatment of progressive radioiodine-refractory differentiated thyroid carcinoma (rrDTC) and medullary thyroid carcinoma (MTC) in Germany. Only recently, based on the randomized trial COSMIC-311, Cabozantinib has been approved as a second-line treatment option in advanced rrDTC. As first in-label selective RET-Inhibitor, Selpercatinib showed promising efficacy in advanced MTC (first line) with RET mutations and rrDTC (second line) with RET fusions along with fewer side effects. Changes and new approaches for the treatment of ATC have been summarised in the current ATA guidelines.

Baseline ctDNA gene alterations as a biomarker of survival after panitumumab and chemotherapy in metastatic colorectal cancer.

Certain genetic alterations and right-sided primary tumor location are associated with resistance to anti-epidermal growth factor (EGFR) treatment in metastatic colorectal cancer (mCRC). The phase 3 PARADIGM trial (n = 802) demonstrated longer overall survival with first-line anti-EGFR (panitumumab) versus antivascular endothelial growth factor (bevacizumab) plus modified FOLFOX6 in patients with RAS wild-type mCRC with left-sided primary tumors. This prespecified exploratory biomarker analysis of PARADIGM (n = 733) evaluated the association between circulating tumor DNA (ctDNA) gene alterations and efficacy outcomes, focusing on a broad panel of gene alterations associated with resistance to EGFR inhibition, including KRAS, NRAS, PTEN and extracellular domain EGFR mutations, HER2 and MET amplifications, and ALK, RET and NTRK1 fusions. Overall survival was prolonged with panitumumab plus modified FOLFOX6 versus bevacizumab plus modified FOLFOX6 in patients with ctDNA that lacked gene alterations in the panel (that is, negative hyperselected; median in the overall population: 40.7 versus 34.4 months; hazard ratio, 0.76; 95% confidence interval, 0.62-0.92) but was similar or inferior with panitumumab in patients with ctDNA that contained any gene alteration in the panel (19.2 versus 22.2 months; hazard ratio, 1.13; 95% confidence interval, 0.83-1.53), regardless of tumor sidedness. Negative hyperselection using ctDNA may guide optimal treatment selection in patients with mCRC. ClinicalTrials.gov registrations: NCT02394834 and NCT02394795 .

Response to immune checkpoint inhibitor combination therapy in metastatic RET-mutated lung cancer from real-world retrospective data

BackgroundThe impact of immune checkpoint inhibitors (ICIs) based treatments on non-small cell lung cancers (NSCLCs) with RET fusions remains poorly understood.MethodsWe screened patients with RET fusions at the First Affiliated Hospital of Zhengzhou University and included those who were treated with ICIs based regimens for further analysis. We evaluated clinical indicators including objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS).ResultsA total of 232 patients with RET fusions were included in the study. Of these, 129 patients had their programmed death-ligand 1 (PDL1) expression levels tested, with 22 patients (17.8%) having a PDL1 level greater than or equal to 50%. Additionally, tumor mutational burden (TMB) status was evaluated in 35 patients, with the majority (30/35, 85.8%) having a TMB of less than 10 mutations per megabase. Out of the 38 patients treated with ICI based regimens, the median PFS was 5 months (95% confidence interval [CI]: 2.4–7.6 months) and the median OS was 19 months (95% CI: 9.7–28.3 months) at the time of data analysis. Stratification based on treatment lines did not show any significant differences in OS (18 vs. 19 months, p = 0.63) and PFS (6 vs. 5 months, p = 0.86). The ORR for patients treated with ICIs was 26.3%. Furthermore, no significant differences were found for PFS (p = 0.27) and OS (p = 0.75) between patients with positive and negative PDL1 expression. Additionally, there was no significant difference in PD-L1 levels (p = 0.10) between patients who achieved objective response and those who did not.ConclusionsPatients with RET fusion positive NSCLCs may not benefit from ICI based regimens and therefore should not be treated with ICIs in clinical practice.

Durable efficacy of selpercatinib in patients with RET fusion+ solid tumors, with a focus on GI tumors: LIBRETTO-001.

746 Background: Selpercatinib, a first-in-class highly selective and potent RET kinase inhibitor with CNS activity, is approved in multiple countries for the treatment of RET-activated cancers. This update includes more patients (pts, n=52) and 16 months (mo) longer follow-up (data cut-off: 13Jan2023) in RET fusion+ solid tumors other than lung/thyroid with a focus on GI histologies. Methods: The phase 1/2 LIBRETTO-001 trial (NCT03157128) enrolled pts with locally advanced/metastatic RET fusion+ solid tumors. 51/52 pts received the recommended dose of 160 mg orally. The efficacy analysis set consisted of pts enrolled ≥6 months prior to the cut-off date. Primary endpoint was objective response rate (ORR) by independent review committee (IRC). Secondary endpoints included ORR by investigator (INV), duration of response (DoR), progression-free survival (PFS), and safety. Results: Of the 52 pts with RET-activated solid tumors other than lung or thyroid, 51.9% were female with a median age of 54.0 years. The majority (31/52) of patients had GI RET fusion+ tumor types, with pancreatic (N=13) and colorectal (N=13) as the most common (Table). 47 pts received prior systemic therapy (median prior lines: 2, range 0-9); 28.8% received ≥3 lines. In 52 efficacy-evaluable pts, confirmed ORR by IRC was 44.2% (23/52, 95% CI: 30.5, 58.7). ORR by IRC for pts with pancreatic tumors was 53.8% and for colorectal tumors was 30.8%. Clinical benefit (complete response + partial response + stable disease ≥16 weeks) was observed in 67.3% (35/52) of pts. Median DoR was 37.2 mo (95% CI: 13.3, NE) for overall pts (Table). No new safety signals were identified compared to previous reports. 4 grade 5 AEs were observed (unrelated to treatment by INV), and 2 pts discontinued due to treatment-related AEs per INV. Conclusions: Selpercatinib continued to demonstrate durable antitumor activity and tolerable safety in pts with RET fusion+ cancers across multiple tumor types and fusion partners, including difficult-to-treat GI cancers with poor results in standard-of-care options, such as pancreatic and colorectal. These results emphasize the importance of comprehensive genomic profiling across all tumor types in order to identify actionable oncogenic drivers, including RET fusions. Clinical trial information: NCT03157128 .[Table: see text]

Real-world testing, treatment patterns, and outcomes following liquid biopsy in advanced cholangiocarcinoma.

455 Background: Cholangiocarcinoma (CCA) is an aggressive cancer with a poor prognosis. Given failure rates of up to 27% of CCA tissue biopsies, liquid biopsy has become an important tool to identify actionable molecular alterations. It is estimated tissue-based testing identifies IDH1 mutations and FGFR2 fusions in 12% and 9% of patients with advanced CCA (aCCA), respectively. Here we examined the rate of molecular alteration detection using circulating tumor DNA (ctDNA) testing, treatment patterns in aCCA, and outcomes for patients receiving ivosidenib following ctDNA-detected IDH1 mutations. Methods: Real-world data was sourced from GuardantINFORM, which comprises aggregated commercial payer health claims and de-identified records from >330,000 patients with clinical ctDNA testing via Guardant360 (G360), from 2014 to 2023. Patients with aCCA and >1 treatment claim after G360 results were included (N=1726). Patient outcomes were assessed via real-world time to treatment discontinuation (rwTTD), real-world time to next treatment (rwTTNT), and real-world overall survival (rwOS), all assessed in months. Log rank test was used to compare Kaplan-Meier survival curves. Results: Of 1495 patients with >1 ctDNA alteration detected, a guideline-recommended biomarker was identified in 18% of patients. In patients with intrahepatic CCA (n=403), 11% had an IDH1 mutation, 9% an FGFR2 fusion, 1% MSI-H detected, 1% BRAF V600E mutation, <1% ERBB2 amplification and <1% RET fusion. Testing was performed prior to first-line therapy, after first-line therapy and after second-line therapy in 34%, 46% and 21% of patients respectively. Gemcitabine and cisplatin represented the most common first-line therapy (48%). FOLFOX (21%), gemcitabine and cisplatin (13%), and capecitabine (11%) were the most common second-line therapies. Among ivosidenib-naïve patients with an IDH1 mutation, 58 (20%) started therapy within 90 days of ctDNA test: 36% received ivosidenib, 57% received chemotherapy, 7% received other therapy. Patients with IDH1 mutations treated with ivosidenib (n=21) had numerically improved rwTTD and rwTTNT compared to those receiving chemotherapy (n=33) [rwTTD: 4.6 (95% CI:2.6-8.6) vs 2.8 (95% CI:2.0-6.3), p=0.1011; rwTTNT 11.0 (95% CI:5.7-NE) vs 5.2 (95% CI:3.3-NE); p=0.2559]. There was no difference in rwOS between patients receiving ivosidenib vs not. However, sample size was small. Conclusions: The rate of actionable molecular alterations detected via ctDNA is 18%, comparable to reports from tissue-based testing. Patients with aCCA are often tested before starting first or second LOT. Patients with ctDNA-detected IDH1 mutations treated with ivosidenib and had a trend toward improved rwTTD and rwTTNT, although it did not reach statistical significance. This data supports the clinical utility of liquid biopsy to identify aCCA patients who may benefit from targeted therapy.

Incidence and genomic characteristics of gene fusions in a large Chinese colorectal cancer cohort.

192 Background: Gene fusion is rare in colorectal cancer (CRC). With the advent of fusion-targeted therapeutics, such as entrectinib for NTRK fusion and selpercatinib for RET fusion, the identification of gene fusions holds clinical significance. Reports providing a comprehensive description of fusions in CRC are limited, and understanding the molecular characteristics of CRC with fusions will contribute to efficient fusion screening. Here, we investigate the incidence and genomic features of gene fusions in a large Chinese CRC population. Methods: We systematically analyzed next-generation sequencing results of tumor tissue from 5534 CRC patients between January 2020 and August 2023. The sequencing panel covers 769 cancer-related genes and can detect fusions, single nucleotide variants and indels, and microsatellite instability (MSI). Statistical significance was determined using chi-square test. Results: Overall, the median age of patients was 62 years (inter-quartile range [IQR]: 53-70), and 40% were female. Gene fusions were detected in 4.4% (242/5534) of all the patients. The incidence is 0.98% (54/5534) if only reported clinically actionable fusions are considered. The median age of the 242 fusion-positive patients was 64 years (IQR: 54-70), and 43% were female. The most highly detected potentially actionable gene fusions were NTRK (0.89%) and FGFR (0.81%), accounting for 39% of the fusion-positive patients. The other fusion genes were ERBB2 (0.52%), RET (0.38%), BRAF (0.31%), EGFR (0.27%), ALK (0.22%), MET (0.09%) and ROS1 (0.07%). Consistent with previous reports, patients with MSI-High were more likely to have fusions compared with those with microsatellite stability (MSS) or MSI-Low (9.9% vs 4.0%, p < 0.001). Besides, RAS or BRAF mutated patients accounted for 59% of the cohort, of whom 2.5% (83/3273) had fusions detected, while 7.0% (159/2261) of the RAS and BRAF wildtype patients had positive fusions ( p < 0.001). Moreover, 404 (7.3%) patients had RNF43 splice or truncating mutations, and gene fusions were detected in 12.9% of these patients. Combining these markers increased the detection rate of fusions, with 28% (33/118) of the RAS/ BRAF wildtype and MSI-H patients having fusions detected. Furthermore, in patients with wildtype RAS/BRAF and MSI-H and RNF43 splice or truncating mutations, the fusion detection rate was as high as 49% (32/65), including 24 patients with actionable fusions of definite clinical significance. Conclusions: Gene fusions were detected in 4.4% of the Chinese CRC population and tended to occur in patients with wildtype RAS/BRAF, MSI-H, or RNF43 mutations. Combining the mutational status of RAS, BRAF, and RNF43 along with MSI status can improve the fusion detection rate and help select candidates for fusion testing and targeted therapy.

The Diagnostic Utility of Repeat Fine-needle Aspirations of Benign Thyroid Nodules.

Objective This study aims to analyze the diagnostic utility of multiple repeat FNA on thyroid nodules with initially benign diagnosis. Methods In a 5-year period, 1658 thyroid nodules with initially benign FNAs were retrospectively reviewed and followed for subsequent resection and repeat biopsy. Results Out of 2150 thyroid nodules, 1658 (77.1%) were diagnosed as benign on FNAs. The average age was 57.4 years (range 11-93 years), and most were females (83.8%). Repeat FNA was performed on 183 benign nodules, of which 141 (8.5%) were sampled a second time and 42 (2.5%) had 2 or more repeat samplings. For the benign nodules without repeat FNAs, 124 had benign resection. Of cases with one-time repeat FNA, most (n=101) remained benign on repeat FNAs, 13 of which were benign on resection. Eleven had atypical repeat FNAs, 5 were resected, 4 of which were benign and one was atypical follicular neoplasm with HRAS and TERT promoter mutations. Of cases with multiple repeat FNA, most (n=35) were still benign on repeat FNAs, one had benign resection. Two had atypical repeat biopsies, one was PTC on resection with CCD6::RET fusion. The positive predictive value significantly decreased from 41.1% on single FNA to 8.3% on one-time repeat (p<0.001) and 16.7% on multiple repeat (p=0.002). The total cost for workup of previously benign nodules was $285,454. Conclusions Repeat FNA biopsies did not provide an additional diagnostic value in the evaluation of benign thyroid nodules, and often led to unwarranted follow-up procedures and significantly increased health care cost.

Characteristics and Survival Outcomes of Patients With Metastatic RET Fusion-Positive Solid Tumors Receiving Non-RET Inhibitor Standards of Care in a Real-World Setting.

RET fusions are oncogenic drivers across different solid tumors. However, the genomic landscape and natural history of patients with RET fusion-positive solid tumors are not well known. We describe the clinical characteristics of RET tyrosine kinase inhibitor (TKI)-naïve patients with RET fusion-positive solid tumors (excluding non-small-cell lung cancer [NSCLC]), treated in a real-world setting and assess the prognostic effect of RET fusions. Data for RET TKI-naïve patients with metastatic solid tumors (excluding NSCLC) who had ≥one Foundation Medicine comprehensive genomic profiling test (January 1, 2011-March 31, 2022) were obtained from a deidentified nationwide (US-based) clinicogenomic database. The primary objective of this study was to compare the overall survival (OS) of patients with RET fusion-positive tumors versus matched patients with RET wild-type (RET-WT) tumors. Patients with RET-WT solid tumors were matched (4:1) to patients with RET fusion-positive tumors on the basis of preselected covariates. The study population included 26 patients in the RET fusion-positive cohort, 7,220 patients in the RET-WT cohort (before matching), and 104 patients in the matched RET-WT cohort. Co-occurring genomic alterations were rare in the RET fusion-positive cohort. Median OS was consistently lower in patients with RET fusion-positive tumors versus those with RET-WT tumors, using three different analyses (hazard ratios, 2.0, 1.7, and 2.2). These data suggest that RET fusions represent a negative prognostic factor in patients with metastatic solid tumors and highlight the need for wider genomic testing and use of RET-specific TKIs that could improve patient outcomes. Our study also highlights the value of real-world data when studying rare cancers or cancers with rare genomic alterations.

The frequency of mutations in advanced thyroid cancer in Japan: a single-center study.

We analyzed the outcomes of genetic testing to study the frequency of mutations in advanced thyroid cancer in Japan. Patients (n = 96) with unresectable or metastatic thyroid carcinoma were included for retrospective chart review. Results of gene panel testing, which was performed between May 2020 and April 2023, were analyzed. The median age of the patients was 73.5 years (range, 17-88); 59 were women, and 39 were men. Overall, 17 patients had anaplastic thyroid carcinoma (ATC), 68 had papillary thyroid carcinoma (PTC), 7 had follicular thyroid carcinoma, and 6 had poorly differentiated thyroid carcinoma (PDTC). Of the 81 patients with differentiated thyroid carcinoma (DTC) and PDTC, 88.9% were radioactive iodine-refractory, and 32.7% of all cases had previously been treated with multiple kinase inhibitors. Of ATC cases, 52.9% had BRAF mutations, and 5.9% had RET fusion. Of PTC cases, 83.1% had BRAF mutations, 9.2% had RET fusion, and 1.5% had NTRK fusion. One case each of ATC and PTC had a tumor mutation burden of ≥10. ATC cases had a significantly higher prevalence of TP53 alterations than the other cases (82.3% vs. 11.8%), whereas the frequencies of TERT promoter mutations were 88.2% in ATC cases and 64.7% in the other cases, albeit without a significant difference. In conclusion, 58.8% of ATC, 93.8% of PTC, and 42.9% of PDTC had genetic alterations linked to therapeutic agents. Active gene panel testing is required to increase treatment options.

Current status of molecular diagnostics for lung cancer.

The management of lung cancer (LC) requires the analysis of a diverse spectrum of molecular targets, including kinase activating mutations in EGFR, ERBB2 (HER2), BRAF and MET oncogenes, KRAS G12C substitutions, and ALK, ROS1, RET and NTRK1-3 gene fusions. Administration of immune checkpoint inhibitors (ICIs) is based on the immunohistochemical (IHC) analysis of PD-L1 expression and determination of tumor mutation burden (TMB). Clinical characteristics of the patients, particularly age, gender and smoking history, significantly influence the probability of finding the above targets: for example, LC in young patients is characterized by high frequency of kinase gene rearrangements, while heavy smokers often have KRAS G12C mutations and/or high TMB. Proper selection of first-line therapy influences overall treatment outcomes, therefore, the majority of these tests need to be completed within no more than 10 working days. Activating events in MAPK signaling pathway are mutually exclusive, hence, fast single-gene testing remains an option for some laboratories. RNA next-generation sequencing (NGS) is capable of detecting the entire repertoire of druggable gene alterations, therefore it is gradually becoming a dominating technology in LC molecular diagnosis.

Chapter 11: Pediatric Differentiated Thyroid Cancers

ABSTRACT The document discusses pediatric differentiated thyroid cancer (DTC), focusing on papillary thyroid carcinoma (PTC), which is increasingly prevalent globally, including in India. Despite a more aggressive initial presentation in children, the long-term prognosis is generally positive. Key differences between pediatric and adult DTC are highlighted, such as a higher risk of malignancy in children with thyroid nodules and common RET/PTC gene rearrangements. There is a debate on the age cutoff for defining pediatric DTC, but the document suggests that 18 years is considered appropriate in the Indian context. Diagnostic methods, including ultrasonography-guided fine needle aspirate (FNA) and the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), are emphasized. The importance of genomic analysis for indeterminate cytology is also proposed. Treatment approaches involve total thyroidectomy due to higher multifocality in children, with consideration of potential complications. Post-operative risk stratification, utilizing the TNM staging system, is seen as crucial and correlates with disease-free survival. Post-operative staging includes TSH-stimulated thyroglobulin (Tg) and anti-thyroglobulin antibody (ATg) levels, along with a diagnostic whole-body 131I scan to assess surgical completeness. Radioactive iodine therapy (RAI) is recommended for iodine-avid persistent/metastatic disease, with an empirical activity of 30 mCi for remnant ablation and adjustments based on age or weight. Regular follow-ups include monitoring TSH-suppressed Tg, Anti-Tg levels, and neck ultrasound. Dynamic risk stratification at 2 years refines risk based on treatment responses. Genetic considerations reveal prevalent RET fusion oncogene and less common BRAF mutations, which are associated with RAI refractoriness. In summary, the document provides a comprehensive understanding of pediatric DTC, emphasizing the need for tailored guidelines in the Indian context. It covers various aspects of diagnosis, surgery, and post-operative care, with a focus on age-appropriate management and ongoing research in this specialized field.

Chemotherapy-free treatment targeting fusions and driver mutations in KRAS wild-type pancreatic ductal adenocarcinoma, a case series.

KRAS wild-type (WT) pancreatic ductal adenocarcinoma (PDAC) represents a distinct entity with unique biology. The therapeutic impact of matched targeted therapy in these patients in a real-world setting, to date, is less established. The aim of our study was to review our institutional database to identify the prevalence of actionable genomic alterations in patients with KRAS-WT tumors and to evaluate the therapeutic impact of matched targeted therapy in these patients. We reviewed electronic medical records of patients with KRAS-WT PDAC and advanced disease (n = 14) who underwent clinical-grade tissue ± liquid next-generation sequencing (315-648 genes for tissue) between years 2015 and 2021. Demographic and disease characteristics were summarized using descriptive parameters. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Of 236 PDAC patients, 14 had advanced/metastatic disease with KRAS-WT tumors. Median age at diagnosis was 66 years. There was a high frequency of potentially actionable genomic alterations, including three (21%) with BRAF alterations, two (14%) with fusions [RET-PCM1 and FGFR2-POC1B (N = 1 each)]; and one with a druggable EGFR (EGFR E746_A755delISERD) variant; two other patients had an STK11 and a MUTYH alteration. Five patients were treated with matched targeted therapy, with three having durable benefit: (i) erlotinib for EGFR-altered tumor, followed by osimertinib/capmatinib when MET amplification emerged (first-line therapy); (ii) pralsetinib for RET fusion (fifth line); and (iii) dabrafenib/trametinib for BRAF N486_P490del (third line). Duration of time on chemotherapy-free matched targeted therapy for these patients was 17+, 11, and 18+ months, respectively. Sustained therapeutic benefit can be achieved in a real-world setting in a subset of patients with advanced/metastatic KRAS-WT PDAC treated with chemotherapy-free matched targeted agents. Prospective studies are warranted.

Genomic Landscape of NSCLC in the Republic of Ireland

IntroductionThe identification of genomic “targets” through next-generation sequencing (NGS) of patient’s NSCLC tumors has resulted in a rapid expansion of targeted treatment options for selected patients. This retrospective study aims to identify the proportion of patients with advanced NSCLC in the Republic of Ireland whose tumors harbor actionable genomic alterations through broad NGS panel testing. MethodsInstitutional review board approval was obtained before study initiation. Patients with NSCLC whose tumors underwent genomic testing through the largest available NGS panel at a nationally funded Cancer Molecular Diagnostics laboratory (St. James’s Hospital) between June 2017 and June 2022 were identified. Patient demographics and tumor-related data were collected by retrospective review from all cancer centers in Ireland, referring to the Cancer Molecular Diagnostics laboratory. A total of 203 (9%) tumor samples were excluded due to insufficient neoplastic cell content. Genomic data were collected through retrospective search of Ion Reporter software. The spectrum and proportion of patients with oncogenic driver mutations were evaluated using descriptive statistics (SPSS version 29.0). ResultsIn total, 2052 patients were identified. Patients were referred from 23 different hospital sites and all four geographic regions (Leinster = 1091, 53%; Munster = 763, 37.2%; Connacht = 191, 9.3%; Ulster = 7, 0.3%). Median age was 69 (range: 26–94) years; 53% were male. The most common tumor histologic subtype was adenocarcinoma (77%, n = 1577). An actionable genomic alteration was identified in 1099 cases (53%), the most common of which was KRAS (n = 657, 32%). Less frequently, NSCLC tumors harbored the following: MET exon 14 skipping (n = 53, 2.6%), MET amplification (n = 26, 1.3%), EGFR (n = 181, 8.8%), HER2 (n = 35, 1.7%), and BRAF (n = 72, 3.5%) mutations. Fusions were detected in 76 patients (3.7%) including ALK (n = 44, 58%), RET (n = 11, 14.5%), ROS1 (n = 16, 21%), and FGFR3 (n = 5, 6.6%), whereas no NTRK fusion was identified. Co-alterations were detected in 114 patients (5.6%), the most common of which was KRAS/PIK3CA (n = 19, 17%), EGFR/PIK3CA (n = 10, 8.5%), and KRAS/IDH1 (n = 9, 8%). Other co-alterations of interest identified included KRAS G12A/ROS1 fusion (n = 1) and KRAS G12C/BRAF G469A (n = 2). ConclusionsThis is the first retrospective study to comprehensively characterize the genomic landscape of NSCLC in Ireland, using the broadest available NGS panel. Actionable alterations were identified in 53.4% of the patients, and KRAS was the most common oncogenic driver alteration. Our study revealed a lower prevalence of patients whose tumor harbors ALK, ROS1, and RET fusions, compared with similar data sets.

Chinese expert consensus on the diagnosis and treatment of advanced RET fusion-positive non-small cell lung cancer (2023 edition)

Lung cancer is the most common cancer and the leading cause of cancer death in China. Non-small cell lung cancer (NSCLC) is the most common histological type of lung cancer. Mutations of driver genes have major impacts on incidence and progression of lung cancer. Advances in molecular biology research and clinical research have promoted the discovery of rare tumor driver genes, as well as the development and application of new targeted drugs. Nearly 1% to 2% of NSCLCs harbor RET fusions, and this patient population may not respond well to traditional treatments like chemotherapy or radiation therapy. After the new highly selective RET inhibitors pralsetinib (BLU-667) and selpercatinib (LOXO-292) entered clinical application, the diagnosis and treatment of RET fusion positive NSCLC has made breakthrough progress. At present, there is a lack of guiding consensus on the standardized diagnosis and treatment of RET fusion-positive NSCLC in China. The Society of Cancer Precision of Chinese Anti-Cancer Association and Lung Cancer Expert Group of Chinese Medical Journal, invited 38 experts form respiratory medicine, medical oncology, oncology radiotherapy and pathology to form a consensus development group. Based on the existing research evidence, combined with China's clinical practice experience, a standardized process for the diagnosis and treatment of advanced RET fusion-positive NSCLC is proposed, including suitable populations and methods for RET gene fusion, treatment drug selection, treatment of resistance to highly selective RET inhibitors, and management of adverse reactions to treatment, with a view to providing guidance for clinicians.

Characterization of the Thyroid Cancer Genomic Landscape by Plasma-Based Circulating Tumor DNA Next-Generation Sequencing.

Background: The limited availability of targeted therapies in thyroid cancer (TC) has challenged conventional treatment algorithms and has established urgency for the identification of targetable genomic abnormalities. In addition to widely adopted tissue-based next-generation sequencing (NGS), plasma-based circulating tumor DNA (ctDNA) NGS is rapidly emerging as a genomic biomarker detection method and is steadily gaining utility across solid tumors. To date, plasma-based genomic alterations in TC have not been determined. Herein, we profile potential actionable mutations detected through ctDNA in patients with TC subtypes. Methods: A retrospective data analysis of the Guardant Health, Inc. database was performed using the commercially available Guardant360® plasma-NGS test on TC samples from adult patients collected between 2016 and 2021. The landscape of genomic alterations and blood tumor mutation burden (bTMB) were analyzed in patients with different types of TC: anaplastic TC (ATC), papillary TC (PTC), follicular TC (FTC), oncolytic carcinoma of the thyroid (OCA), poorly differentiated TC (PDTC), medullary TC (MTC), and TC not otherwise specified (TC NOS). Results: Of the 1094 patients included most of the patients n = 876 had TC NOS, and 20% had a specific diagnosis (92 ATC, 62 PTC, 14 FTC, 16 OCA, 2 PDTC, and 32 MTC patients). The median age was 65 (range 10-98) and 47.3% were male. 78.3% of patients had one or more genomic alteration detected by ctDNA NGS. TP53 (46.9%) was the most common mutation detected among all TC. BRAFV600E was detected in 27.2% of ATC, 35.7% of PTC, and in none of FTC. RAS was detected in 18.5% of ATC, 11.9% of PTC, and 62.5% of FTC. RET, ALK, and NTRK fusions were seen in 1.1%, 0.5%, and 0.2% of all TC, respectively. RET mutations were detected in 66.7% of MTC. bTMB analysis was performed on 159 patients. The mean bTMB was higher in ATC compared with other types of TC (p = 0.0011, 0.0557, and <0.0001, respectively). Conclusions: Plasma-based comprehensive NGS is a promising NGS method in TC; however, future validation of the clinical utility by analysis of paired tumor and plasma samples is needed.

Characterizing Genetic Alterations Related to Radioiodine Avidity in Metastatic Thyroid Cancer.

Patients with differentiated thyroid cancer (DTC) with distant metastasis (DM) are usually not recognized as radioactive iodine (RAI)-refractory DTC in a timely manner. The elucidation of genetic features related to RAI uptake patterns may shed light on the early recognition of RAI-refractory DTC. This work aimed to elucidate the underlying molecular features behind different RAI uptake patterns. A total of 214 patients with DM-DTC were retrospectively included in the analysis. RAI uptake patterns were defined as initially RAI refractory (I-RAIR) and initially RAI avid (I-RAIA) according to the first post-treatment scan, then I-RAIA was further divided into continually RAIA (C-RAIA), partly RAIR (P-RAIR), and gradually RAIR (G-RAIR) according to subsequent scans. The molecular subtype groups-BRAFV600E mutated, RAS mutated, fusions, and others-were classified according to main driver genes status. BRAF, TERT promoter, and TP53 mutations are more frequently detected in the I-RAIR pattern while RET fusions and RAS mutations are more frequent in the I-RAIA pattern. A late-hit mutation including TERT, TP53, or PIK3CA is more common in I-RAIR than that in I-RAIA (50.0% vs 26.9%, P = .001), particularly for those with RAS mutations in the I-RAIR group, always accompanied by TERT promoter. Isolated RET fusions accounts for 10% of I-RAIR. When compared among driver gene groups, BRAFV600E-mutated tumors have a higher rate of the I-RAIR pattern (64.4%) than RAS-mutated (4.5%, P < .001) and fusion-positive (20.7%, P < .001) tumors. In I-RAIA subgroups, BRAFV600E-mutated tumors have lower prevalence of the C-RAIA pattern than those with RAS mutation or fusions. Patients with the I-RAIR pattern predominantly featured mutations of the BRAF and/or TERT promoter, of which RAS mutations were usually accompanied by late-hit mutations, while fusions mostly occurred alone.

Whole-exome sequencing explored mechanism of selpercatinib resistance in RET-rearranged lung adenocarcinoma transformation into small-cell lung cancer: a case report

Small cell transformation was one mechanism by which EGFR-mutation NSCLC acquired resistance after tyrosine kinase inhibitors (TKIs) treatment. A few reports of small cell transformation occurred in other oncogene-driven lung cancers. We found the first case of transformation of a RET-rearranged lung adenocarcinoma to SCLC after selpercatinib, a novel highly selective RET TKIs. Whole-exome sequencing (WES) was used to explore alteration in gene expression in tumor tissue at initial diagnosis and after transformation into small cell carcinoma. We found that transformed into SCLC tumor tissue had inactivation of RB1 and TP53, with RET fusion was still present. In addition, the APOBEC family of cytidine deaminases appeared amplification. Although RET rearrangement still existed, using another RET TKIs was ineffective, and etoposide plus platinum might be an effective rescue treatment.

Abstract B145: Clinical features of progression and outcomes with subsequent therapies in patients treated with RET-inhibitors

Abstract Background: RET fusions can be found in 1-2% of patients (pts) with advanced non-small cell lung cancer (aNSCLC). While targeted treatment with RET inhibitors (RETi) has significantly improved prognosis, resistance eventually develops. Current knowledge regarding the pattern of disease progression and the optimal therapeutic sequence for patients treated with RETi is limited. Methods: We conducted a retrospective multicentric collection of clinical and biological data on pts with RET-rearranged (RET+) aNSCLC treated with first-generation RETi. Patients with a progression-free survival (PFS) period of less than 8 months on RETi were classified as poor responders. We investigated the clinical patterns of disease progression (PD) and outcomes with subsequent therapies, evaluated by the overall response rate (ORR by investigator assessment) and PFS. PFS2 was calculated from RETi start to PD after subsequent line. Results: 173 pts from 32 centres were identified. Median age was 65, 61% were female, 41% were smokers, 81% had an ECOG performance status &amp;lt;2, 95% had adenocarcinoma, 18% had brain metastasis, 76% had RETi in first or second line. The administered RETi were selpercatinib in 55%, pralsertinib in 42%, other first generation RETi in 3% of pts. After a median follow up of 30.4 months (mo) (95%CI 26-32.1), 84 pts (48.6%) had PD after RETi, with a median PFS (mPFS) of 15.6 mo (95%CI 12.2-23.3) and an ORR of 72.2%. Radiological PD patterns included multisite PD in 46 (71%), oligoPD in 15 (23%), mixed response in 4 (6%). 7/15(47%) received local treatment while continuing RETi. Subsequent treatment line after RETi was administered in 37 pts (21%). Considering chemotherapy-based treatments, ORR and mPFS were 46% and 5.52 mo (4.07-11.3) overall, 57% and 4.53 mo (95%CI 1.4-NA) in 9 pts with chemo-immunotherapy, 27% and 5.88 mo (95%CI 2.1-NA) in 11 pts with platinum-doublet, 83% and 10.4 mo (8.28-NR) in 6 pts with bevacizumab plus chemotherapy (p=0.77 vs chemotherapy alone). Targeted therapy was administered in 8 patients: 6 received RETi after RETi (first generation) with 33% ORR and 3.83 mo (1.77-NR) mPFS, one patient had crizotinib plus RETi to target MET amplification found at resistance, with a PFS of 5.95 mo, one had alectinib alone, targeting SQSTM1-ALK fusion found at resistance, with PD after 1.58 mo. Cabozantinib was chosen for one pt, with a PFS of 5.52 mo and obtaining PR; one pt was treated with single-agent immunotherapy, with rapid PD after 1 month; one pt had an investigational antibody-drug conjugate, experiencing SD and a 4 mo PFS. PFS to subsequent treatment was not different between long and poor responders to RETi (13 and 15 pts,5.88 vs 4.53 m, respectively, p=0.75); PFS2 was longer in good responders to RETi (25 vs 16 mo,p=0.012). Conclusions: Disease progression to RETi most frequently involved multiple sites. Chemotherapy plus bevacizumab seemed to perform better than chemotherapy alone or chemo-immunotherapy. The benefit of tailored treatment basing on the molecular profile at PD needs to be further explored. Citation Format: Arianna Marinello, Wael Salem Zrafi, Giacomo Massa, Fabrizio Tabbò, Fabrizio Citarella, Filippo Gustavo Dall'Olio, Lindsay Colin, Emilio Bria, Giulio Metro, Josè Nicolas Minatta, Antonio Calles, Isabelle Monnet, Marco Tagliamento, Hortense Gaultier De Saint Basile, Nicolas Girard, Arianna Pagliaro, Diego Luigi Cortinovis, Judith Raimbourg, Carol Zanchetta, Giannis Mountzios, Frank Aboubakar Nana, Safae Terrisse, Alessandro Russo, Patricia Iranzo, Clarisse Audigier-Valette, Philippe Rochigneux, Vincent Fallet, Michael Duruisseaux, Sophie Cousin, Florian Guisier, Laura Mezquita, Jordi Remon, Anas Gazzah, David Planchard, Benjamin Besse, Mihaela Aldea. Clinical features of progression and outcomes with subsequent therapies in patients treated with RET-inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B145.

Abstract A036: A subset of lung adenocarcinomas defined by high-level ERBB2 amplification is vulnerable to HER2-targeted therapy

Abstract Background: Most lung adenocarcinomas (LUAD) are driven by activation of receptor tyrosine kinases (RTK). HER2 (encoded by ERBB2) is an RTK capable of ligand-independent dimerization and signaling when overexpressed. ERBB2 amplification (ERBB2amp) is a common cause of HER2 overexpression. While activating ERBB2 mutations (e.g., ERBB2 exon 20 YVMA insertions) are targetable drivers of LUAD, the role of ERBB2amp in lung cancer (LC) is unclear and there is no FDA-approved therapy for this indication in LC. Here, we report the clinicopathological and molecular characteristics of LUAD with high-level ERBB2amp and investigate the efficacy of HER2-targeted agents in LC models with ERBB2amp. We also demonstrate the clinical benefit of trastuzumab-deruxtecan (T-DXd) in a patient with ERBB2amp LUAD. Design: An institutional database of hybrid capture DNA NGS panel targeting 290-447 genes (v1-v3.1) was interrogated for LUAD with high-level ERBB2amp (defined as at least 6 calculated gene copies by NGS). HER2 immunohistochemistry (IHC) was performed on 29 available cases and scored according to ASCO/CAP scoring criteria. HER2 IHC scores of 2+ and 3+ were considered overexpression. Two LC cell lines, H2170 and CALU3 were identified as ERBB2amp and their responses to HER2 inhibitors were characterized with Western blotting, viability, and apoptosis assays. CALU3 and H2170 xenograft models were also established and treated with HER2 inhibitors or T-DXd. Results: ERBB2amp was identified in 31/3,684 (0.8%) LUAD patients. HER2 overexpression was present in 24 out of 29 evaluable cases (79.3%). Eighteen cases (58%) showed high-level ERBB2amp with no concurrent drivers and were more likely to be male (P = 0.001) and have a history of tobacco use (P = 0.001), compared to patients with high-level ERBB2amp with a concurrent driver mutation (activating ERBB2 SNV/indels, activating EGFR and MET mutations, RET fusion). H2170 and CALU3 cells displayed overexpression of HER2 and phospho-HER2, and growth of these cells showed sub-nanomolar sensitivity to trastuzumab and T-DXd, and low nanomolar sensitivity to afatinib. T-DXd induced apoptosis in both cell lines (assessed by activation of caspase 3/7 and elevation of BIM and cleaved PARP levels). While trastuzumab and afatinib significantly slowed down growth of H2170 and CALU3 xenografts, only T-DXd achieved tumor shrinkage equivalent to partial (H2170) or complete response (CALU3) in all animals. We describe the case of a LUAD patient with a RET rearrangement who acquired high-level ERBB2amp after progression on selpercatinib and was treated with T-DXd, with evidence of disease stability and clinical benefit. Conclusion: High-level ERBB2 amplification detected by NGS reliably predicts HER2 overexpression in lung adenocarcinoma. LUAD with ERBB2 amplification and no concurrent oncogenic drivers is a rare event that occurs predominantly in male smokers. This data can inform future trials investigating the utility of HER2-targeting agents in this population. Citation Format: Igor Odintsov, Maisam Makarem, Sara E. Bachert, Tom Zhang, Romel Somwar, Pasi A. Jänne, Lynette M. Sholl. A subset of lung adenocarcinomas defined by high-level ERBB2 amplification is vulnerable to HER2-targeted therapy [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A036.