Tissue Next-generation Sequencing Research Articles

Analysis of the resistance profile of real-world alectinib first-line therapy in patients with ALK rearrangement-positive advanced non-small cell lung cancer using organoid technology in one case of lung cancer.

Alectinib has achieved excellent therapeutic efficacy in anaplastic lymphoma kinase (ALK) fusion gene-positive non-small cell lung cancer (NSCLC) patients, however, patients eventually develop resistance to it. Exploring the gene variant mapping after alectinib resistance provides a basis for the whole management of ALK-positive advanced NSCLC. This study aimed to characterize the mutation profiles of real-world ALK rearrangement-positive advanced NSCLC patients after first-line alectinib treatment resistance. The research also investigated the treatment options and coping strategies after resistance. Clinical data of patients with advanced NSCLC who received first-line alectinib treatment in the First Affiliated Hospital of Guangzhou Medical University between November 2018 and April 2022 were collected. Moreover, next-generation sequencing (NGS) data of the patient's baseline and post-resistance tissues were gathered. One patient underwent lung cancer organoid culture and drug sensitivity testing. Out of 35 first-line alectinib-treated patients with advanced NSCLC, 31 are presently in progression-free survival (PFS; 4.3-35.0 months). Four patients experienced progressive disease, and all of them were sequentially treated with ceritinib. Tissue NGS results before sequential treatment in three patients indicated an echinoderm microtubule-associated protein-like 4-ALK fusion that remained at the original baseline, and the PFS for ceritinib treatment was 0.5-1.3 months. One patient developed acquired resistance mutations in the structural domain of ALK protein kinase (V1180L and E1161D), and the PFS for ceritinib treatment was 6.7 months. For one patient who maintained original baseline ALK rearrangement positive without acquired mutation after progression of ceritinib resistance, lung cancer-like organ culture with sequential brigatinib and lorlatinib led to a PFS of 3.2 and 1.9 months, respectively, which aligned with the corresponding drug susceptibility testing results for this patient. For ALK rearrangement-positive patients, blind sequencing of other second-generation tyrosine kinase inhibitors (TKIs) or third-generation lorlatinib may not guarantee satisfactory tumor suppression following first-line second-generation ALK-TKI alectinib administration for treatment progression. NGS testing of patients' blood or tissue samples after disease progression may provide insight into the etiology of alectinib resistance. Patient-sourced drug sensitivity testing of lung cancer-like organs selects drug-sensitive medications based on NGS results and provides a reference for subsequent drug therapy for patients after drug resistance, particularly those who remain ALK rearrangement-positive at baseline.

Liquid biopsy in patients with metastatic pancreatic cancer using an optimized targeted sequencing approach: Data from the pancreatic cancer registry PanDaDETECT.

e16303 Background: Metastatic pancreatic ductal adenocarcinoma (PDAC) conveys a dismal prognosis, and biomarkers for clinical diagnostics and treatment monitoring are urgently needed. Detection of circulating tumor DNA (ctDNA) using liquid biopsy (LB) has been shown to correlate with treatment response in other tumor entities. Here, we evaluated the feasibility of LB by targeted next generation sequencing (NGS) in metastatic PDAC, using an NGS approach optimized for PDAC. Methods: Patients from our PanDaDETECT registry with metastatic PDAC were included. Plasma samples were collected at initial diagnosis and every three months during palliative treatment. Targeted NGS of plasma samples was performed using a small, custom-generated gene panel optimized for LB provided by Qiagen (QiaSeq Targeted DNA Panel), covering the four most frequently mutated genes in PDAC with full exon coverage (KRAS, TP53, SMAD4 and CDKN2A). Sequencing was performed on the Illumina NextSeq 550 platform. LB results were compared to matched tissue NGS data from tumor samples. Results were correlated with the serological biomarker Ca 19-9 and radiographic response data. All patients provided written informed consent. The responsible ethics committee approved the study. Results: From 2020 to 2022, 57 patients were included and underwent plasma NGS at least at initial diagnosis. For 52 of these patients a tissue NGS result was available, and in 49 patients (94,2%), at least one of the four genes covered by our LB panel was mutated in the tumor tissue. In 35 patients, our LB approach detected ctDNA in the plasma sample at initial diagnosis (61,4%). Comparing tissue and plasma sequencing data at initial diagnosis, our LB approach detected ctDNA in 32 out of 49 patients who had a known mutation in tissue NGS in at least one of the four genes covered by the LB panel (65,3%). For 22 patients with positive ctDNA detection in plasma NGS, follow-up plasma samples after three months of treatment were available. In this subgroup, detection of ctDNA showed a superior correlation with radiographic response assessed by RECIST criteria than the serological biomarker Ca 19-9. In patients with a partial response or stable disease as defined by RECIST, ctDNA levels decreased markedly, while remaining elevated in patients showing disease progression. For 11 patients, plasma NGS at 6 months of treatment or later was performed, the results at these later time points correlated well with clinical and radiographic response in 9 out of 11 patients. Conclusions: Our LB approach optimized for PDAC is feasible and shows a good correlation with serological and radiographic response. Our optimized NGS panel covering only four genes is able to detect ctDNA in a majority of PDAC patients. LB by targeted NGS has the potential to detect a broad spectrum of relevant mutations in PDAC in an automatable and cost-effective matter.

Effect of plasma-based molecular testing in patients with newly diagnosed advanced NSCLC on initiation of targeted agents in patients with targetable genomic alterations: A real world experience from the Middle East.

e20514 Background: The treatment of metastatic non-small cell lung cancer ( m-NSCLC) is personalized and driven by mutational profiling of the tumour tissue at diagnosis. This study evaluates the additional clinical utility of plasma based molecular testing towards shortening time to initiation of treatment and detection of targetable mutations in a cohort of patients with newly diagnosed m-NSCLC. Methods: This is a retrospective analysis of patients with newly diagnosed advanced NSCLC referred to the Thoracic Oncology Program between September 2021 to December 2023, who underwent “paired” plasma based circulating tumour ( ct-DNA ) and tissue based next generation sequencing (NGS) testing (done less than 4 weeks apart). ct-DNA testing was performed using the Oncomine Pancancer NGS Assay (Thermo Scientific) that screens for single nucleotide variants (SNV) in hotspot regions of 52 and common fusions involving 12 genes respectively. Tissue NGS testing was performed using Oncomine Comprehensive Assay Plus (Thermo Scientific); a panel covering ~500 genes capable of identifying all single nucleotide variants, indels, fusions and copy number variants (CNV). Patient demographics and clinicopathological characteristics were collected by retrospective review of electronic medical records (EMR). Results: Among 36 patients, the median age was 66.0 years (range: 32-66), 25 (69.4%) were males, and 16 (44.4%) were never smokers. Thirty (83.3%) had adenocarcinoma and 33 (91.67%) had stage IV NSCLC. The mutation detection rate of ct-DNA was 66.7% with a concordance of 58.3% between ct-DNA and tissue NGS testing. The median turnaround time (TAT) from sample collection to reporting were12 days (IQR:8-15) and 14 days (IQR:9-24.50) for ct-DNA and tissue NGS testing respectively. Among 31 patients who started treatment, the median time to initiation of 1st line treatment was 26 days from date of first visit (IQR:18-42). Fifteen(41.7%), 6(16.7%) and 10(27.8%) started first line targeted therapy, chemotherapy and chemoimmunotherapy respectively. Twenty-three(63.89%) had targetable mutations (EGFR Exon 19 or 21, EGFR Exon 20 insertion, ALK, ROS1, MET Exon1 4 skipping, ROS1 or KRAS12C detected either in ct-DNA or tissue). Fifteen (65.21%) out of these 23 started targeted therapy as their 1st line treatment and of these 8 (53.3%) were initiated on targeted agents prior to availability of tissue NGS reports. Conclusions: Though our TAT for ct-DNA and tissue based NGS testing was similar, ct-DNA based NGS testing enables earlier initiation of targeted treatment for newly diagnosed advanced NSCLC patients with targetable mutations. In the real world, this increases access to targeted agents and may translate to a subsequent improvement in survival outcomes.

Utilizing comprehensive next-generation sequencing to determine the clinical significance of copy number variation in advanced/metastatic non-small cell lung cancer.

e15174 Background: Large population-based comprehensive tumor genomic profiling using next-generation sequencing (NGS) technology offers insight into the detection of copy number variation (CNV) in advanced/metastatic solid cancers. However, the significance and role of CNV in advanced-stage non-small cell lung cancer (NSCLC) is limited. In this analysis, we investigated the incidence and impact of CNV on patient outcomes. Methods: Patients were recruited as part of an ongoing real-world multicentre prospective NSCLC Precision Oncology Programme in Hong Kong. All patients underwent tissue and liquid NGS using Foundation One CDx and Foundation One Liquid CDx, respectively. Patients were classified into two groups based on CNV status: group 1 (CNV+) was defined as tumors with CNV reported; group 2 (CNV-) was defined as tumors with no CNV reported. The association of clinical factors with CNV was reported using Chi-square tests. The overall survival (OS) was calculated from the date of diagnosis of advanced-stage cancer to the date of death or the last follow-up date. Survival analysis was estimated using the Kaplan-Meier method with the log-rank test. Results: 353 patients were included in this analysis. NGS was performed in 216 (61%) tumor tissues, and 137 (39%) liquid specimens. 37% (n = 129) were female, and 50% (n = 175) were ever-smoker. 63% (n = 223) of our patient cohort harbored druggable mutations. The detection rate of CNV was 74% in tissue and 14% in liquid specimens. Patients with brain, liver, or bone metastasis (p = 0.018) and/or TMB-high (TMB-H) (p = 0.0014) were associated with CNV+. Next, we assessed the impact of CNV on treatment outcomes. Among patients who received immunotherapy ± chemotherapy, CNV+ was associated with a median OS of 20.4 months compared to 31.4 months in the CNV- group (HR:2.09, 95% CI: 1.05-4.16, p = 0.034). In contrast, there was no statistically significant difference in OS among the CNV+ and CNV- patient groups treated with chemotherapy alone. Although not significant, there was a trend towards poorer OS to immunotherapy ± chemotherapy in the TMB-H CNV+ cohort (23.6 months versus 31.4 months; p = 0.082). Conclusions: We demonstrate the significance of CNV as a prognostic tool for the prediction of survival outcomes among lung cancer patients. Our data suggests that CNV represents a distinct entity in advanced/metastatic NSCLC, associated with poorer survival outcomes to immunotherapy.

Utility of an amplicon-based ctDNA platform for advanced cholangiocarcinomas (CCA) in Asia.

e16206 Background: Cholangiocarcinoma represents a major cause of cancer mortality in Asia. While clinical outcomes have improved with the addition of anti-PD1/PDL1 agents to standard-of-care chemotherapy for advanced disease, recent data suggests that novel agents against IDH1 mutations, FGFR2 and NTRK rearrangements, BRAF V600E mutations, and microsatellite instability (MSI) are effective. Tumor-based next generation sequencing (NGS) is routinely recommended by guidelines but is limited by tissue availability and quality in patients with unresectable disease. A comprehensive circulating tumor DNA-based (ctDNA) NGS platform offers an acceptable alternative, but its clinical utility and pickup rate for oncogenic drivers remain unknown. Methods: In our multi-national cohort of advanced CCA across 5 countries, we explored the utility of Lucence LiquidHALLMARK (LHM), a Medicare-reimbursed, amplicon-based NGS ctDNA platform targeting 80 cancer related genes, 10 fusions, and MSI. Performance of LHM has been previously reported. Data was retrieved in-house by a de-identified centralized database and pooled for analysis. Here, we report the demographic and genomic findings of our cohort and highlight the impact of testing on actionable molecular alteration discovery. Results: Between Jan 2020 and Dec 2023, 60 samples from 56 patients (62.5% male) with advanced CCA in Hong Kong SAR (50.0%), Singapore (41.1%), Thailand (3.6%), Philippines (3.6%), and Malaysia (1.8%) underwent LHM testing. Metastatic disease accounted for 83.9% and 8.9% had locally advanced disease. Median age was 67 years (range 33-88), with 34% and 30% of tests obtained during first-line therapy and at diagnosis respectively. Only 6 cases had available tissue NGS results. Analysis on 56 baseline samples showed an 80.4% discovery rate (45/56 patients) for ≥1 molecular alterations. A median of 2 variants (mean 3.27) was detected per sample, with variant allele fraction ranging from 0.05% to 66.5%. Importantly, 8.9% (5/56) of patients harbored ≥1 actionable variants, including 3 with FGFR2 rearrangements ( FGFR2- WAC, FGFR2- ACTR1A, FGFR2- CAMK2D) and 2 with BRAF V600E drivers. A further 3 patients had potentially druggable variants in IDH2 and FGFR3 and 12 harbored BRCA1/2 variants, of which 4 were deleterious. None of the samples had MSI. Top 10 mutated genes were TP53 (48%), KRAS (21%), BRCA2 (18%), PIK3CA (11%), TERT (9%), CDKN2A (9%), SMAD4 (9%), FGFR2 (7%), BRAF (7%), and CDK6 (5%). Limited histopathological and treatment outcomes are available in the current dataset. Conclusions: Our advanced cholangiocarcinoma cohort of 56 patients from 5 Asian countries showed that an amplicon based ctDNA liquid biopsy platform overcomes the tissue-related challenges of genomic profiling specific to unresectable biliary tumors. We showed an 80.4% discovery rate for any molecular alterations and a 8.9% pickup rate for variants with strong actionability.

Utility of an amplicon-based ctDNA platform for advanced cholangiocarcinomas (CCA) in Asia.

e16206 Background: Cholangiocarcinoma represents a major cause of cancer mortality in Asia. While clinical outcomes have improved with the addition of anti-PD1/PDL1 agents to standard-of-care chemotherapy for advanced disease, recent data suggests that novel agents against IDH1 mutations, FGFR2 and NTRK rearrangements, BRAF V600E mutations, and microsatellite instability (MSI) are effective. Tumor-based next generation sequencing (NGS) is routinely recommended by guidelines but is limited by tissue availability and quality in patients with unresectable disease. A comprehensive circulating tumor DNA-based (ctDNA) NGS platform offers an acceptable alternative, but its clinical utility and pickup rate for oncogenic drivers remain unknown. Methods: In our multi-national cohort of advanced CCA across 5 countries, we explored the utility of Lucence LiquidHALLMARK (LHM), a Medicare-reimbursed, amplicon-based NGS ctDNA platform targeting 80 cancer related genes, 10 fusions, and MSI. Performance of LHM has been previously reported. Data was retrieved in-house by a de-identified centralized database and pooled for analysis. Here, we report the demographic and genomic findings of our cohort and highlight the impact of testing on actionable molecular alteration discovery. Results: Between Jan 2020 and Dec 2023, 60 samples from 56 patients (62.5% male) with advanced CCA in Hong Kong SAR (50.0%), Singapore (41.1%), Thailand (3.6%), Philippines (3.6%), and Malaysia (1.8%) underwent LHM testing. Metastatic disease accounted for 83.9% and 8.9% had locally advanced disease. Median age was 67 years (range 33-88), with 34% and 30% of tests obtained during first-line therapy and at diagnosis respectively. Only 6 cases had available tissue NGS results. Analysis on 56 baseline samples showed an 80.4% discovery rate (45/56 patients) for ≥1 molecular alterations. A median of 2 variants (mean 3.27) was detected per sample, with variant allele fraction ranging from 0.05% to 66.5%. Importantly, 8.9% (5/56) of patients harbored ≥1 actionable variants, including 3 with FGFR2 rearrangements ( FGFR2- WAC, FGFR2- ACTR1A, FGFR2- CAMK2D) and 2 with BRAF V600E drivers. A further 3 patients had potentially druggable variants in IDH2 and FGFR3 and 12 harbored BRCA1/2 variants, of which 4 were deleterious. None of the samples had MSI. Top 10 mutated genes were TP53 (48%), KRAS (21%), BRCA2 (18%), PIK3CA (11%), TERT (9%), CDKN2A (9%), SMAD4 (9%), FGFR2 (7%), BRAF (7%), and CDK6 (5%). Limited histopathological and treatment outcomes are available in the current dataset. Conclusions: Our advanced cholangiocarcinoma cohort of 56 patients from 5 Asian countries showed that an amplicon based ctDNA liquid biopsy platform overcomes the tissue-related challenges of genomic profiling specific to unresectable biliary tumors. We showed an 80.4% discovery rate for any molecular alterations and a 8.9% pickup rate for variants with strong actionability.

Abstract PO2-20-08: Metastatic Lung Cancer Masquerading as Metaplastic Breast Cancer

Abstract Background Metaplastic breast carcinoma (MBC) is an unusual malignancy that presents a diagnostic challenge due to the presence of varying cytomorphologies that can be seen in benign and malignant tumors. We posit that metastatic disease to the breast, itself an uncommon entity, should be considered in the differential diagnosis of MBC. We report a unique case of metastatic non-small cell lung cancer (NSCLC) with an actionable driver mutation that presented as a symptomatic breast mass and was initially considered to represent MBC. Report A 74-year-old woman with a 22-pack-year smoking history presented to the breast clinic complaining of a palpable left breast mass that had grown rapidly over the previous month. Ultrasound-guided biopsy of the breast mass revealed high-grade poorly differentiated carcinoma. On immunohistochemical (IHC) evaluation, tumor cells were strongly positive for epithelial markers CAM5.2 and keratin AE1/AE3, weakly positive for breast cancer (BC) marker TRPS1, and negative for BC marker GATA3, squamous cell carcinoma markers p63 and CK5, and melanoma marker SOX10. Metaplastic triple-negative BC was diagnosed. However, concern remained for metastasis from a non-breast primary tumor due to the patient’s constitutional symptoms such as fatigue, night sweats, and 60-pound unintentional weight loss over the previous year, as well as interval development of a suspicious nodular rash on her right upper extremity. An FDG-PET-CT was obtained and demonstrated a hypermetabolic left lung consolidation (maximum SUV 33.3) measuring 7.2 cm, pulmonary nodules, and extensive thoracic lymphadenopathy. Due to rising suspicion for a primary lung tumor, additional IHC staining on the original breast biopsy was requested. Tumor cells were positive for TTF-1, consistent with metastatic lung adenocarcinoma. Tissue next-generation sequencing (NGS) identified a MET exon 14 skipping mutation, making the patient eligible for treatment with capmatinib, a first-line kinase inhibitor targeted therapy for metastatic NSCLC. At the time of this report, the patient has completed a course of palliative stereotactic body radiation therapy to the left lung and started capmatinib 400 mg BID, which she is tolerating well. Her first restaging scans after treatment initiation will be obtained one week after the time of this report. Conclusion In the absence of heightened suspicion for a non-breast primary tumor, our patient had initially received a diagnosis of triple-negative MBC. This diagnosis would have exposed her to increased treatment-related toxicities from cytotoxic chemotherapy and poor prognosis from MBC without survival benefit from targeted therapy for NSCLC. We advocate for the use of supplemental body imaging, expert and comprehensive IHC evaluation, and multidisciplinary discussion in cases of MBC and undifferentiated breast malignancy to facilitate accurate diagnosis and treatment. Citation Format: Tanmayi Pai, Marte Wasserman, Jason Lewis, Miglena Komforti, James Jakub, Augustine Lee, Yanyan Lou, Pooja Advani, Rohit Rao. Metastatic Lung Cancer Masquerading as Metaplastic Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-20-08.

The cost-effectiveness of including liquid biopsy into molecular profiling strategies for newly diagnosed advanced non-squamous non-small cell lung cancer in an Asian population

ObjectivesLiquid biopsy is complementary to tissue biopsy for lung cancer profiling, yet evidence of the cost-effectiveness is limited. This could retard implementation and reimbursement in clinical practice. The aim of this study is to estimate the cost-effectiveness of profiling strategies that include liquid biopsy and to identify the optimal profiling approach for newly diagnosed advanced non-squamous non-small cell lung cancer (NSCLC) in an Asian population using Singapore as an example. Materials and methodsA decision tree and partitioned-survival model was developed from the Singapore healthcare system’s perspective to evaluate the cost-effectiveness of five molecular profiling strategies: either tissue or plasma next-generation sequencing (NGS) alone, a concurrent, and two sequential approaches. Model inputs were informed by local data or published literature. Sensitivity analyses and scenario analyses were undertaken to understand the robustness of the conclusions for decision making. The optimal strategy at different willingness-to-pay (WTP) thresholds was presented by cost-effectiveness acceptability frontier and the expected loss curve. ResultsThe sequential tissue-plasma NGS approach revealed an additional 0.0981 quality adjusted life years (QALYs) for an extra cost of S$3,074 over a 20-year time horizon compared to tissue NGS alone, resulting in an incremental cost-effectiveness ratio (ICER) of S$31,318/QALY and an incremental net monetary benefit of S$1,343 per patient. The findings were sensitive to the costs of pembrolizumab and osimertinib and the probabilities of re-biopsy after tissue NGS. Sequential plasma-tissue NGS and plasma NGS alone were more costly and less effective than alternatives. ConclusionThe sequential tissue-plasma NGS approach generated the highest net monetary benefit and was the optimal testing strategy when WTP was S$45,000/QALY. It retained superiority but understandably with a higher ICER when expensive, non-first line treatments were included. Overall, its routine clinical practice should be proactively considered for newly diagnosed advanced non-squamous NSCLC in an Asian population.

Abstract 2498: Assessing the clinical value of ctDNA sequencing for initial tumor profiling in metastatic colorectal cancer patients with sufficient tumor tissue

Abstract Introduction Tumor profiling including RAS, BRAF, HER2, and MSI/MMR status, is required to determine the treatment for patients with metastatic colorectal cancer (mCRC) at the time of diagnosis. While comprehensive tumor profiling using tissue-based next-generation sequencing (NGS) is increasingly adopted for initial profiling in mCRC, the role of circulating tumor DNA (ctDNA) NGS as initial testing in patients with sufficient tumor tissue is not clearly understood. We assessed the clinical value of ctDNA sequencing compared to tumor NGS in patients with newly diagnosed mCRC who have sufficient tumor specimens. Methods We prospectively enrolled consecutive patients with newly diagnosed mCRC at the National Cancer Center Korea. As per the institutional protocol for mCRC, initial tumor profiling was performed on primary tumor tissue using an in-house NGS panel (NCC PCP ver.3), which included 525 genes. For ctDNA sequencing, patients were evaluated using the AlphaLiquid®100 comprehensive cancer panel (IMBdx, Inc.), which included 118 genes, before the initiation of chemotherapy. Additionally, immunohistochemical (IHC) testing for HER2 and polymerase chain reaction (PCR)/IHC testing for MSI and/or MMR were performed to assess the accuracy of HER2 and MSI/MMR status. Results A total of 188 patients were enrolled. In 139 eligible patients, 275 potentially actionable mutations were found in 12 selected CRC-related genes (APC, TP53, KRAS, NRAS, BRAF, FBXW7, PIK3CA, ERBB2, SMAD4, NF1, EGFR, MET). Of these, 32% were found both in ctDNA and tissue; 54% were found in ctDNA only; 12% in tissue only, and 2% were discordant. For RAS/BRAF mutations, which are required for anti-EGFR treatment decisions, the concordance rate between ctDNA and tissue NGS was 83.1%, and the concordance was higher in patients with higher ctDNA concentrations. For 9 patients with potentially actionable copy number variations (CNV) in EGFR, HER2, MET, and FGFR1, 3 cases were found by both assays; 4 were found by ctDNA only, and 2 were found by tissue only. ctDNA NGS correctly predicted MSI/MMR status in 2 out of 4 patients with MSI-H/dMMR; in the 2 other patients, the MSI and MMR statuses were different, suggesting potential false positivity. In addition, the fold changes in ctDNA dynamics during treatment significantly correlated with changes in tumor size and CEA levels, as well as with droplet digital PCR copy number fold changes. In a patient with MET amplification, ctDNA NGS identified MET Y1230H as a potential acquired resistance mutation after crizotinib treatment, which responded to cabozantinib but not to capmatinib. Conclusions Initial tumor profiling using ctDNA NGS yielded outcomes comparable to those of tumor tissue NGS in guiding treatment for patients with newly diagnosed mCRC, thereby suggesting its utility as an initial profiling method in mCRC. Citation Format: Yongjun Cha, Bun Kim, Dong Woon Lee, Hyun Yang Yeo, Chang Won Hong, Kyung Su Han, Byung Chang Kim, Hee Jin Chang. Assessing the clinical value of ctDNA sequencing for initial tumor profiling in metastatic colorectal cancer patients with sufficient tumor tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2498.

Abstract 6469: The association of mismatch repair gene alterations with elevated tumor mutational burden in microsatellite stable gastrointestinal cancers

Abstract Background: Benefit from single-agent immune checkpoint inhibitor has been observed in 5-10% of the patients with microsatellite stable (MSS) gastrointestinal (GI) cancers. However, a reliable predictive marker to immune checkpoint inhibitor has not been discovered in this patient population. We sought to assess the incidence of mismatch repair (MMR) gene alterations and their association with tumor mutational burden (TMB) in MSS GI cancers. Methods: This is a retrospective cohort study of patients with advanced GI cancer who had molecular profiling of the tumor using either Guardant360 blood-based or Tempus tissue next generation sequencing (NGS) platforms between 2020 and 2023. We assessed four MMR genes including MLH1, MSH2, MSH6 and PMS2 for alterations. Continuous variables were summarized as median and interquartile range (IQR) and compared using Mann-Whitney test. Categorical variables were summarized as counts and proportions and compared using Fisher’s exact test. Results: A total of 2920 patients with Guardant360 were included with a median age of 65 (IQR: 56-73) years. 870 (30%) patients had pancreas cancer; 846 (29%) patients had colorectal cancer; 688 (24%) patients had biliary tract cancers; and the rest had other GI cancers. Among patients evaluable for microsatellite instability (MSI) status, 58 patients (2%) had MSI-high GI cancers, 31 (53%) of whom had MMR gene alterations. 2445 (98%) patients had MSS GI cancers, 130 (5.3%) of whom had MMR gene alterations. Patients with MSS GI cancers bearing MMR gene alterations had a median age of 70 (IQR: 62-75) years, significantly older than those without MMR gene alterations (p<0.001). In addition, patients with MMR gene alterations had significantly higher median blood TMB of 11 (IQR: 7.4-16) mut/Mb compared to 7.7 (IQR: 4.8-11) mut/Mb in patients without MMR gene alterations. In MSS GI cancers, MMR gene alterations are more commonly associated with the presence of alterations in APC (p=0.03), TP53 (p=0.01), CTNNB1 (p<0.001) and SMAD4 (p=0.01). 1453 patients with GI cancer and Tempus tissue NGS data were included as a validation cohort. They had comparable demographics with the Guardant360 cohort. 14 (1.6%) of 896 patients with MSS GI cancers had MMR gene alterations, significantly fewer (p<0.001) than those found in the Guardant360 cohort. Patients with MMR gene alterations and wild type POLE had significantly higher (p=0.001) median TMB of 9.8 (IQR: 4.8-14) mut/Mb compared to 4.7 (IQR: 3.2-6.3) mut/Mb in patients without MMR gene alterations. Conclusions: MMR gene alterations can be identified by clinical NGS platforms in a small proportion of patients with MSS GI cancers. They are associated with elevated TMB, which may suggest a hypermutated profile serving as a basis for potential role of immune checkpoint inhibitor in MSS GI cancers. Citation Format: Conor D. O'Donnell, Mojun Zhu, Hao Xie. The association of mismatch repair gene alterations with elevated tumor mutational burden in microsatellite stable gastrointestinal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6469.

Abstract 6399: Real-world experience of an Asian pan-cancer combined DNA/RNA next generation sequencing (NGS) tissue biopsy assay

Abstract Introduction: Comprehensive molecular profiling with combined DNA-RNA next-generation sequencing (NGS) on tumor tissue is now increasingly being used as standard-of-care for sequence therapy selection to improve cancer survival. Combined DNA-RNA NGS is also considered standard-of-care for central nervous system (CNS) tumor classification. Despite the genetic heterogeneity and diversity of cancers, most commercial combined DNA/RNA NGS assays are validated in Western populations, resulting in knowledge gaps in patient outcomes. We report here for the first time a range of actionable outcomes from a comprehensive DNA/RNA tissue NGS assay designed specifically to probe Asian-prevalent cancers and biomarkers in an international multicenter real-world study in Asia. Methods: 1,002 formalin-fixed paraffin-embedded tissue samples from 995 Asian cancer patients across >70 centers in 7 countries and/or territories underwent real-world DNA/RNA NGS testing in a CAP-accredited CLIA-certified laboratory. Genomic alterations including SNVs, INDELS, gene fusions, CNVs, TMB, and MSI were analyzed using an Asian-centric pan-cancer hybrid-capture NGS panel that comprehensively profiles 572 cancer-related genes and 91 RNA fusion partners (UNITED). Biomarkers were considered actionable if the therapeutic indication in any solid tumor or hematological cancer was FDA-approved, guidelines-recommended, or supported by well-powered phase III clinical trials. Results: 27 cancer types were represented in 1,002 tissue samples, with lung, breast, colorectal, and prostate cancers comprising 45.5% of clinical volume. 79.5% of samples harbored ≥1 actionable biomarker, with the most frequently altered genes being TP53, KRAS, PIK3CA, EGFR, and NF1. Overall, 42.6% of samples had ≥1 biomarker with an indication in the patient’s cancer type, including 81.5% of lung, 59.0% of breast, 61.8% of colorectal, and 42.1% of prostate cancers. Across the pan-cancer cohort, 13.3% was TMB-high and 1.9% was MSI-high. 26.3% of samples were from cancer types outside the original assay design; the top 3 were pancreatic cancer (7.3%), sarcoma (3.3%), and CNS tumor (3.1%). Cancers of unknown primary (CUP) also constituted a significant proportion (3.8%). In CNS tumors, 38.7% harbored an actionable mutation in IDH1, BRAF, or H3-3A. In CUP, 78.8% harbored an actionable mutation; 50% of samples harbored biomarkers that additionally informed potential tumor origin, including mutations in EGFR, MET, ALK, ROS1, and BRCA1. Conclusion: The use of an Asian-focused pan-cancer DNA/RNA NGS panel resulted in detection of actionable biomarkers in 79.5% of clinical cases. These findings support the utility of DNA/RNA NGS assays in informing standard-of-care therapeutic decisions in Asian cancer patients for maximizing cancer survival. Citation Format: Jason Yongsheng Chan, Jing Yi Lee, Zi Yi Wan, Abner Herbert Lim, Tun Kiat Ko, Cedric Chuan-Young Ng, Donald Poon, Jens Samol, Tsz Him So, Su Pin Choo, Ravindran Kanesvaran, Cheng-Vai Hui, Joseph Siu-Kie Au, Aya El Helali, Timothy Yip, Vikneswari Rajasegaran, Sandy Lim, Ruifen Weng, Puay Hoon Tan, Bin Tean Teh, Min-Han Tan, Jonathan Poh. Real-world experience of an Asian pan-cancer combined DNA/RNA next generation sequencing (NGS) tissue biopsy assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6399.

Concurrent Tissue and Circulating Tumor DNA Molecular Profiling to Detect Guideline-Based Targeted Mutations in a Multicancer Cohort

Tissue-based next-generation sequencing (NGS) of solid tumors is the criterion standard for identifying somatic mutations that can be treated with National Comprehensive Cancer Network guideline-recommended targeted therapies. Sequencing of circulating tumor DNA (ctDNA) can also identify tumor-derived mutations, and there is increasing clinical evidence supporting ctDNA testing as a diagnostic tool. The clinical value of concurrent tissue and ctDNA profiling has not been formally assessed in a large, multicancer cohort from heterogeneous clinical settings. To evaluate whether patients concurrently tested with both tissue and ctDNA NGS testing have a higher rate of detection of guideline-based targeted mutations compared with tissue testing alone. This cohort study comprised 3209 patients who underwent sequencing between May 2020, and December 2022, within the deidentified, Tempus multimodal database, consisting of linked molecular and clinical data. Included patients had stage IV disease (non-small cell lung cancer, breast cancer, prostate cancer, or colorectal cancer) with sufficient tissue and blood sample quantities for analysis. Received results from tissue and plasma ctDNA genomic profiling, with biopsies and blood draws occurring within 30 days of one another. Detection rates of guideline-based variants found uniquely by ctDNA and tissue profiling. The cohort of 3209 patients (median age at diagnosis of stage IV disease, 65.3 years [2.5%-97.5% range, 43.3-83.3 years]) who underwent concurrent tissue and ctDNA testing included 1693 women (52.8%). Overall, 1448 patients (45.1%) had a guideline-based variant detected. Of these patients, 9.3% (135 of 1448) had variants uniquely detected by ctDNA profiling, and 24.2% (351 of 1448) had variants uniquely detected by solid-tissue testing. Although largely concordant with one another, differences in the identification of actionable variants by either assay varied according to cancer type, gene, variant, and ctDNA burden. Of 352 patients with breast cancer, 20.2% (71 of 352) with actionable variants had unique findings in ctDNA profiling results. Most of these unique, actionable variants (55.0% [55 of 100]) were found in ESR1, resulting in a 24.7% increase (23 of 93) in the identification of patients harboring an ESR1 mutation relative to tissue testing alone. This study suggests that unique actionable biomarkers are detected by both concurrent tissue and ctDNA testing, with higher ctDNA identification among patients with breast cancer. Integration of concurrent NGS testing into the routine management of advanced solid cancers may expand the delivery of molecularly guided therapy and improve patient outcomes.

Clinical utility of plasma cell-free DNA in pancreatic neuroendocrine neoplasms.

In advanced pancreatic neuroendocrine neoplasms (PanNEN), there are little data detailing the frequency of genetic alterations identified in cell free DNA (cfDNA), plasma-tissue concordance of detected alterations, and clinical utility of cfDNA. Patients with metastatic PanNENs underwent cfDNA collection in routine practice. Next-generation sequencing (NGS) of cfDNA and matched tissue when available was performed. Clinical actionability of variants was annotated by OncoKB. Thirty-two cfDNA samples were analyzed from 25 patients, the majority who had well-differentiated intermediate grade disease (13/25; 52%). Genomic alterations were detected in 68% of patients and in 66% of all cfDNA samples. The most frequently altered genes were DAXX (28%), TSC2 (24%), MEN1 (24%), ARID1B (20%), ARID1A (12%), and ATRX (12%). Twenty-three out of 25 (92%) patients underwent tumor tissue NGS. Tissue-plasma concordance for select genes was as follows:DAXX (95.7%), ARID1A (91.1%), ATRX (87%), TSC2 (82.6%), MEN1 (69.6%). Potentially actionable alterations were identified in cfDNA of 8 patients, including TSC2 (4; level 3b), ATM (1; level 3b), ARID1A (2; level 4), and KRAS (1; level 4). An ETV6:NTRK fusion detected in tumor tissue was treated with larotrectinib; at progression, sequencing of cfDNA identified an NTRK3 G623R alteration as the acquired mechanism of resistance; the patient enrolled in a clinical trial of a second-generation TRK inhibitor with clinical benefit. In metastatic PanNENs, cfDNA-based NGS identified tumor-associated mutations in 66% of plasma samples with a high level of plasma-tissue agreement in PanNEN-associated genes. Clonal evolution, actionable alterations, and resistance mechanisms were detected through circulating cfDNA genotyping.

Association of longitudinal changes of genomic alteration of circulating tumor DNA with treatment response in pancreatic cancer.

701 Background: Recently, the evaluation of circulating tumor DNA (ctDNA) in pancreatic cancer (PC) patients has gained attention for detection of mutation profile. However, the concordance between tissue next-generation sequencing (NGS) and ctDNA NGS remains unclear. Additionally, the dynamics of genomic alterations during treatment or disease progression are not well understood. Methods: In this prospective cohort study conducted at Seoul National University Hospital from Jan 2022, tissue samples from endoscopic ultrasound-guided fine needle biopsies and blood samples were collected from PC patients. Genomic DNA from the treatment naïve primary tissue and ctDNA from the blood obtained before any treatment and during follow-up with anti-cancer treatment were obtained. Genomic alternation was analyzed based on targeted NGS based panel deep sequencing including 41 genes. Results: The concordance of genomic alteration profiles between tissue NGS and ctDNA NGS was evaluated in 55 patients, and the mutation detection rate of patients who were diagnosed as stage I or II disease were 100% (14 of 14) in tissue NGS and 86% (12 of 14) in ctDNA NGS. That of patients who were diagnosed as stage III or IV disease was 92.7% in tissue NGS (38 of 41) and 90% (37 of 41) in blood ctDNA NGS. Among the study patients, the longitudinal changes of genomic mutation profile were evaluated in the patients at the first treatment response assessment, and patients with progressive disease showed significantly greater amounts of mutations including newly detected Tier1/2 variants than baseline and the previous response assessment. Conclusions: In conclusion, there is comparable mutation detection between tissue genomic DNA and blood ctDNA. The significant increase in ctDNA mutations during disease progression suggests their association with immune evasion and cancer evolution. Further studies utilizing our prospective cohort are needed to explore clinical implications of these results.

Comprehensive clinico-molecular profile and efficacy of anti-HER2 therapy for HER2-amplified biliary tract cancer.

544 Background: Biliary tract cancer (BTC) is an aggressive malignancy with poor prognosis and limited treatment options. The prevalence of HER2 amplification in BTC has been reported to be 5-20%, and clinical trials suggested the clinical benefit of HER2-targeted treatment in this disease subpopulation. In a global collaboration, we investigated the comprehensive clinico-molecular characterization as well as the efficacy of anti-HER2 therapy in HER2-amplified BTC. Methods: Patients with advanced BTC who received systemic therapy were included from the GOZILA and MONSTAR studies in Japan and from the COLOMATE trial in the US. Genomic alterations were detected by tissue next-generation sequencing (NGS), including FoundationOne CDx and TempuslxT, and plasma circulating tumor DNA NGS including Guardant360 and FoundationOne Liquid CDx. The clinico-molecular characteristics were evaluated in an exploratory cohort comprised of patients from Japan, whereas the efficacy of anti-HER2 therapy was assessed in a biomarker selected cohort with patients from both Japan and the US. Results: Of 439 patients included in the exploratory cohort, 43 (10%) had HER2 amplification. BTC with primary tumor location in the gallbladder accounted for 58% of primary sites of patients with HER2 amplification. TP53 mutation (84% vs 61%, p=0.003) and BRAF amplification (9% vs 2%, p=0.030) were significantly more frequent in patients with HER2 amplification compared to those without, and no KRAS mutation co-occurred with HER2 amplification. There was no significant difference in overall survival (OS) between patients with and without HER2 amplification (17.7 months [M] vs 16.9 M, hazard ratio [HR] 0.95, 95% confidence interval [CI] 0.65-1.40, p=0.799). Of 58 patients with HER2-amplified BTC included in the biomarker selected cohort (43 Japan, 15 US), 27 (47%) received anti-HER2 therapy. The median OS of patients treated with anti-HER2 therapy was significantly longer than that of patients who did not receive anti-HER2 therapy (24.3 M vs. 12.1 M, HR 0.43, 95% CI 0.23-0.82, p=0.011). Multivariate analysis also identified anti-HER2 therapy as an independent prognostic factor for OS (HR 0.42, 95% CI 0.20-0.85, p=0.015). Conclusions: HER2 amplifications were found in 10% of advanced BTC and did not represent an independent predictive factor for OS. Of clinical significance, patients with HER2-amplified BTC derive a significant benefit from anti-HER2 therapy.

Real-world analysis of patients with advanced gastrointestinal (GI) cancers harboring inactivating TSC1 and TSC2 alterations using the Foundation Medicine genomic database.

558 Background: Genomic profiling of GI tumors can identify potentially actionable genetic alterations, ultimately leading to better outcomes in patients who currently have few treatment options. In exploratory biomarker analyses of patients with perivascular epithelioid cell tumors treated with the mTOR inhibitor nab-sirolimus (AMPECT, NCT02494570), those with inactivating alterations in the tumor suppressor genes TSC1 or TSC2 (critical negative regulators of mTOR activity) had confirmed responses (8/9 patients with inactivating TSC2 alterations and 1/5 patients with inactivating TSC1 alterations). PRECISION 1, a currently enrolling tumor-agnostic study, will evaluate nab-sirolimus in patients with TSC1 or TSC2 alterations. To enumerate the frequency of these alterations in GI cancers, we analyzed data from a real-world genomic database. Methods: Next-generation sequencing (NGS) data from Foundation Medicine’s genomic database of patients with advanced cancer were analyzed using the FoundationInsights web-based platform to identify patients with GI cancers who had inactivating TSC1 or TSC2 alterations (short variants [base substitutions, insertions and deletions], rearrangements, and copy number deletions). Tumor mutational burden (TMB), microsatellite instability status and other mutations were also characterized in this group of patients. Results: As of 29 March 2022, tumor tissue NGS data were available for 5816 patients with GI cancers bearing alterations in TSC1 or TSC2. Of these, 1642 patients had at least one inactivating alteration. The GI tumor types that most frequently expressed inactivating alterations in TSC1 or TSC2 were hepatocellular carcinoma (alterations in 6.5%); colorectal adenocarcinoma (1.7%); gastrointestinal stromal tumors (1.7%); and cholangiocarcinoma (1.6%). Of all 1642 patients, 688 were female, and most (74%) were 51–80 years of age when the sample was obtained. Of patients with inactivating TSC1 and TSC2 alterations, 37.6% were in TSC1 and 62.9% were in TSC2 and included short variants (31.3% and 48.4%), rearrangements (2.7% and 6.6%), and copy number deletions (3.5% and 7.4%), respectively. TMB was low (<6 mutations/megabase) in 58% of patients, and most patients had microsatellite stable (MSS; 71.3%) tumors. Other commonly mutated genes in this cohort were TP53 (62.7%), APC (38.5%) and KRAS (30.4%). Conclusions: TSC1 and/or TSC2 alterations were commonly observed in GI cancers. These cancers were frequently microsatellite stable and of low TMB suggesting that these are actionable alterations that may be candidates for targeted therapy. This hypothesis is being tested in the PRECISION 1 (NCT05103358) trial which is open for enrollment or just-in-time clinical trial sites and available to patients with GI cancers harboring TSC1 or TSC2 alterations.

Survival impact of homologous recombination deficiency in veterans with cholangiocarcinoma including mutual exclusivity with pathogenic KRAS and TP53.

546 Background: Cholangiocarcinoma (CCA) has poor prognosis and limited treatment options. The US Veteran Health Administration’s (VHA) National Precision Oncology Program (NPOP) was established to characterize pathogenic drivers across the integrated VA network. Here, we summarize an important subgroup of CCA with homologous recombination deficiency (HRD) and its impact on overall survival (OS). Methods: Next-generation sequencing (NGS) was performed using FoundationOne CDx Analysis included clinicopathological, molecular alterations including, single nucleotide variants, gene amplification/loss, and gene fusion/rearrangements obtained from centralized data of the VHA’s Corporate Data Warehouse. Homologous recombination deficiency was defined by pathogenic variant mutations (MT) in ARID1A, ATM, ATR, BAP1, BRCA1, BRCA2, CDK12, CHEK2, FANC, NBN, PALB2, and RAD51. Statistical analysis was performed using Chi-squared test for concurrent gene enrichment and log-rank Kaplan-Meier analysis. Results: 483 CCA samples underwent tissue NGS as standard of care. Pathogenic variants in HRD genes included ARID1A (15.5%, n=75), BAP1 (9.5%, n=46), ATM (2.7%, n=13), PALB2 (2.3%, n=11) and BRCA (2.0%, n=10), representing 31.7% (n=153) of the population. HRD mutations were found in similar proportions of localized (31.8%) and metastatic (31.5%) clinical presentations at diagnosis. OS was not significantly different between CCA with HRD mutations (12.3 mo WT vs. 13.8 months with HRD MT, p=64). KRAS MT (n=77, 15.9% of population) did not impact OS (WT 12.3 mo v. MT 13.1 mo) including subgroup analysis stratified by HRD status. There was increased frequency in KRAS MT with HRD WT 18.5% versus HRD MT10.4% (p<0.03). Additionally, there was increased frequency in TP53 MT with HRD WT 54.8% versus HRD MT 28.1% (p<0.00001). TP53 MT (n=224, 46.3% of population) conferred inferior OS (WT 12.3 mo v. MT 13.1 mo) including subgroup analysis stratified by HRD status. Subgroup analysis of TP53 MT had worsened OS with concurrent HRD MT (n=39, 4.1 mo) v. HRD WT (n=158, 9.0 mo; p<0.04). Conclusions: Across a diverse integrated healthcare system of Veterans, mutations associated with HRD were found to be common, however, not prognostic in OS across a diverse patient population of CCA. Further work is needed to clarify exposure to platinum containing chemotherapy. TP53 MT CCA remains a critical unmet need that drives worsened outcomes including here in patients with mutations in HRD. Future analysis should consider mutation signatures of HRD, loss in heterozygosity of HRD, and platinum exposure to further define the subgroups of CCA with mutations in HRD. [Table: see text]

Rapid and reliable testing for clinically actionable EGFR mutations in non-small cell lung cancer using the IdyllaTM platform: a real-world two-center experience in Greece

ABSTRACT Background Limited information exists on epidermal growth factor receptor (EGFR) molecular epidemiology in Greece. Next-generation sequencing (NGS) is the recommended method for EGFR genotyping in NSCLC. The Idylla Biocartis platform is a fully automated system for actionable EGFR mutation detection. Research design and methods We describe the prevalence of EGFR mutations in NSCLC patients in two high-volume clinical centers in Greece and compare key methods used for their determination. Eight hundred and fifty-seven FFPE samples from NSCLC patients were tested for EGFR mutations at University of Crete (UoC; n = 324) and at Evangelismos Hospital, Athens (Evangelismos; n = 503). Results The prevalence of EGFR mutations was 11.1% in the whole cohort (11.5% in non-squamous). The detection rate was 11.0% by NGS, 9.8% by Sanger and 11.3% by Idylla for the whole cohort (12.0% in non-squamous). The agreement between Idylla and Sanger was 93.2%. A targetable EGFR mutation was detected in 10.0% using tissue NGS alone, and in 16.0% using concurrent Idylla ctEGFR testing. Conclusion The frequency of EGFR mutations was as expected for a Caucasian population. The Idylla EGFR test performance is comparable to reference methods and with a shorter TAT. Adding a concurrent plasma Idylla test to tissue NGS testing increases the detection rate of EGFR mutations in NSCLC.

Molecular and Clinicopathologic Characterization of Mismatch Repair-Deficient Endometrial Carcinoma Not Related to MLH1 Promoter Hypermethylation

Universal tumor screening in endometrial carcinoma (EC) is increasingly adopted to identify individuals at risk of Lynch syndrome (LS). These cases involve mismatch repair-deficient (MMRd) EC without MLH1 promoter hypermethylation (PHM). LS is confirmed through the identification of germline MMR pathogenic variants (PV). In cases where these are not detected, emerging evidence highlights the significance of double-somatic MMR gene alterations as a sporadic cause of MMRd, alongside POLE/POLD1 exonuclease domain (EDM) PV leading to secondary MMR PV. Our understanding of the incidence of different MMRd EC origins not related to MLH1-PHM, their associations with clinicopathologic characteristics, and the prognostic implications remains limited.In a combined analysis of the PORTEC-1, -2, and -3 trials (n = 1254), 84 MMRd EC not related to MLH1-PHM were identified that successfully underwent paired tumor–normal tissue next-generation sequencing of the MMR and POLE/POLD1 genes. Among these, 37% were LS associated (LS-MMRd EC), 38% were due to double-somatic hits (DS-MMRd EC), and 25% remained unexplained. LS-MMRd EC exhibited higher rates of MSH6 (52% vs 19%) or PMS2 loss (29% vs 3%) than DS-MMRd EC, and exclusively showed MMR-deficient gland foci. DS-MMRd EC had higher rates of combined MSH2/MSH6 loss (47% vs 16%), loss of >2 MMR proteins (16% vs 3%), and somatic POLE-EDM PV (25% vs 3%) than LS-MMRd EC. Clinicopathologic characteristics, including age at tumor onset and prognosis, did not differ among the various groups.Our study validates the use of paired tumor–normal next-generation sequencing to identify definitive sporadic causes in MMRd EC unrelated to MLH1-PHM. MMR immunohistochemistry and POLE-EDM mutation status can aid in the differentiation between LS-MMRd EC and DS-MMRd EC. These findings emphasize the need for integrating tumor sequencing into LS diagnostics, along with clear interpretation guidelines, to improve clinical management. Although not impacting prognosis, confirmation of DS-MMRd EC may release patients and relatives from burdensome LS surveillance.

Plasma ddPCR for the detection of MET amplification in advanced NSCLC patients: a comparative real-world study

Background: Mesenchymal–epithelial transition ( MET) amplification is a crucial oncogenic driver and a resistance mechanism to epidermal growth factor receptor tyrosine kinase inhibitors (TKIs) of non-small-cell lung cancer (NSCLC). Fluorescence in situ hybridization (FISH) is the gold standard for MET amplification detection. However, it is inapplicable when tissue samples are unavailable. Objective: This study assessed the performance of plasma droplet digital polymerase chain reaction (ddPCR) in MET amplification detection in NSCLC patients. Design and methods: A total of 87 NSCLC patients were enrolled, and 94 paired tissue and plasma samples were analyzed for the concordance between FISH and plasma ddPCR/tissue next-generation sequencing (NGS) in detecting MET amplification. In addition, the efficacy of patients with MET amplification using different detection methods who were treated with MET-TKIs was evaluated. Results: Plasma ddPCR showed substantial concordance with FISH (74.1% sensitivity, 92.5% specificity, and 87.2% accuracy with a kappa value of 0.68) and outperformed tissue NGS (kappa value of 0.64) in MET amplification detection. Combined plasma ddPCR and tissue NGS showed substantial concordance with FISH (92.3% sensitivity, 89.2% specificity, and an accuracy of 90.1% with a kappa value of 0.77). The efficacy is comparable in these NSCLC patients with MET amplification detected by FISH and plasma ddPCR who were treated with MET-TKIs. Conclusion: Plasma ddPCR is a potentially reliable method for detecting MET amplification in advanced NSCLC patients. Combined plasma ddPCR and tissue NGS might be an alternative or complementary method to MET amplification detection.