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How can patients with lung cancer undergo standardized genetic testing?
Lung cancer can be classified as non-small cell lung cancer (NSCLC) and small cell lung cancer according to tissue type. In patients with advanced NSCLC who are not inoperable to resect, systemic drugs are an important treatment to improve prognosis. With the development of medical standards, many new targeted drugs and immunotherapy drugs continue to come out, adding new treatment strategies for NSCLC patients. For patients with advanced NSCLC, before the doctor formulates a treatment plan, the patient must generally be histologically tested to understand the oncological characteristics before the most appropriate drug can be used. In addition, among the early NSCLC patients who can be surgically resected, there are also targeted adjuvant therapy indications approved in China, which has gradually reflected the trend of precision medication. In short, the treatment of NSCLC is inseparable from the theory of "precision treatment and detection first".
Compared with Western populations, the gene variation profile of mainland NSCLC patients has some differences. In this regard, the Medical Oncology Channel sorted out the contents of China's "Clinical Practice Guidelines for Molecular Pathological Detection of Non-small Cell Lung Cancer (2021 Edition)" (hereinafter referred to as the "Guidelines for Molecular Pathology Detection")[1], and invited Professor Lu Dehong of Changtu County Central Hospital in Liaoning Province and Professor Zhang Zheng of Luotian County People's Hospital in Hubei Province to share the clinical practice in combination with the clinical practice for readers.
Different genetically abnormal populations should be individualized
By selecting accurate, rapid and appropriate detection methods, the target population of suitable targeted drugs can be screened, which is of great significance for clinical diagnosis and treatment. In addition to the more common EGFR/ALK gene, with the continuous discovery of other driver genes with low incidence, coupled with the gradual clarification of the mechanism of acquired drug resistance after targeted drug therapy, the clinical requirements for genetic testing are getting higher and higher. Similarly, the application of drugs such as immunotherapy PD-1/PD-L1 inhibitors is inseparable from the screening of beneficiary populations.
The occurrence of driver gene mutations in mainland NSCLC is different from that of European and American populations, including EGFR (45%-55%), KRAS (8%-10%), ALK (5%-10%), ROS1 (2%-3%), MET (2%-4%), HER2 (2%-4%), BRAF (1%-2%), RET (1%-4%), NTRK (<1%), NRG1/2 (<1%), FGFR2 (1%), FGFR2 (1%), <1%), etc. [1-2]. These driver genes are universally mutually exclusive and can occur simultaneously in rare cases. In addition, molecular pathological detection related to immunotherapy includeSRupport expression, tumor mutation burden (TMB), and microsatellite instability/mismatch repair (MSI/MMR).
At present, for targets such as EGFR/ALK/ROS1/MET/RET, there are already corresponding targeted drugs listed in China. For example, the drugs targeted for the treatment of EGFR-sensitive mutations with variant types include gefitinib, erlotinib, ektinib, afatinib, dacotinib, ostriptynib, ametinib; klotinib, ensatinib, aletinib, and seritinib for ALK fusion/rearrangement; and sivatinib for meta14 exon jump mutations.
Who needs genetic testing? When to check? The Guidelines for Molecular Pathology Testing classify:
(1) Patients with advanced lung adenocarcinoma need to undergo genetic testing, in the mainland, the currently listed targeted drugs are used, and the corresponding genes that clearly need to be accompanied by diagnosis include EGFR, ALK, ROS1 and MET, and the target genes that have corresponding targeted drugs but have not yet been listed in China include HER2, BRAF, KRAS, NTRK, NRG1/2, FGFR2, etc. At present, there are also corresponding RET inhibitors approved in China.
(2) For patients with advanced lung squamous cell carcinoma, target molecular gene testing can be recommended.
(3) Patients with EGFR and ALK-negative advanced NSCLC, if PD-1/PD-L1 antibody drug immunotherapy is proposed, PD-L1 expression testing is recommended, and TMB testing can be selected.
For the above-mentioned gene mutation detection in NSCLC, common molecular pathology detection methods include Sanger sequencing, fluorescence in situ hybridization (FISH), fluorescence quantitative PCR (qRT-PCR), immunohistochemistry (IHC), and second-generation sequencing (NGS).
Detection of EGFR/ALK/ROS1/MET and PD-L1 expressions
EGFR
EGFR gene variants include genetic mutations (point mutations, insertion/deletion mutations), mainly occurring in exons 18 to 21, as well as acquired resistance mutations (including T790M resistance mutations of first- and second-generation EGFR targeted drugs and C797S, third-generation TKI-resistant mutations). These patients are more likely to choose qRT-PCR or second-generation sequencing, or other types of detection.
FROM ALK
ALK gene variant types include gene rearrangement/fusion, and acquired resistance mutations (predominantly point mutations). At least 20 more EML4-ALK fusion variant subtypes have been identified. The Guidelines for Molecular Pathology Testing recommend that IHC-Ventana D5F3 be prioritized for ALK testing. When quality problems are suspected of detecting specimens, FISH testing is preferred.
ROS1
ROS1 gene variants include ROS1 gene rearrangement. Before IHC detection ROS1 protein expression is used for initial screening ROS1 fusion clinical application, the laboratory should go through a strict testing process, interpretation standards, quality control and assurance, and positive cases need to be verified by other technical platforms. When interpreting FISH, qRT-PCR, and next-generation sequencing results, other technology platforms should be recommended for patients whose test results are uncertain, whose signal is atypical, or who are at critical values. When detected with other genes (e.g., EGFR, ALK, etc.), qRT-PCR or next-generation sequencing can be performed.
PD-L1 expression
IHC detection of PD-L1 expression levels in tumor cells and/or immune cells is currently the primary means of assessing whether patients with NSCLC can benefit more from immune checkpoint inhibitor therapy. At present, The Mainland has approved three standardized commercial kits for PD-L1 detection for clinical testing, including the PD-L1 IHC 22C3 pharmDx kit and concentrate supporting the Dako platform, the PD-L1 IHC 28-8 pharmDx kit and the SP263 kit supporting the Ventana assay platform. Unlisted assays also include the SP142 kit based on the Ventana assay platform. The use of different monoclonal antibody and IHC staining platforms and the setting of positive truncation values for PD-L1 staining are related to the efficacy of the corresponding immunotherapy drugs.
WITH
There are many types of abnormalities in the MET pathway, and the detection of EXON-skipping mutations and MET amplifications is currently focused on. MET amplification includes primary amplification and secondary amplification, of which secondary amplification is more common after TKI treatment progression in driver gene-positive patients, and is one of the important mechanisms of EGFR-TKI treatment resistance.
Methods for detecting MET14 exon-skipping mutations include second-generation sequencing or qRT-PCR direct detection of mRNA missing MET exon 14, or second-generation sequencing at the DNA level that can detect genetic variants that may lead to metatome of EXON 14. RNA-based detection should pay attention to mRNA quality in clinical practice, and quality control in situ hybridization detection should be done before detection is the standard method for detecting MET amplification. Different FISH interpretation criteria [Cappuzzo standards and UCCC (University of Colorado Cancer Center) standards] are used in clinical studies, and in clinical practice it is recommended to use UCCC standards that can distinguish between site-directed amplification and polyploidy as much as possible. Compared with FISH, second-generation sequencing can be used for MET amplification detection, but the correspondence with FISH detection is more complicated and may miss MET multibody, but second-generation sequencing can achieve multi-gene co-examination and is more widely used in clinical practice.
Expert reviews
01 Professor Lu Dehong: Precision treatment, testing first
Professor Lu Dehong said that at present, there are still many aspects of NSCLC genetic testing in domestic clinical practices that need to be improved in terms of standardized paths and quality control processes. He pointed out that the state of the driving gene is an important basis for the treatment selection of NSCLC, and genetic testing is the most basic part of clinical work, and the test results determine the direction of future treatment, so genetic testing must first ensure its accuracy. In addition, patients who do not have access to tissue samples often require liquid biopsy, but the sensitivity and specificity of liquid biopsy still need to be improved to improve detection rates. Finally, large Panel polygenic testing still needs to be further refined to cover all tumor-related genes to better guide patients' standardized and individualized treatments.
02 Prof. Zheng Zhang: Experience sharing of genetic testing in NSCLC patients
Professor Zhang Zheng shared his experience in genetic testing in patients with advanced non-squamous NSCLC based on clinical work experience. First, with the improvement of the availability of drugs for different target therapies, it is recommended that patients use large panes to detect common and rare targets such as EGFR/ALK/ROS1/MET/RET when the patient's economic conditions permit. If the patient drives the gene negative, PD-L1 expression levels should also be measured to guide the patient's immunotherapy. Secondly, the detection specimen should be preferred tissue specimen detection, and if the patient is difficult to puncture or unwilling to puncture, blood specimen detection can also be selected, which has a high sensitivity. In addition, for patients with malignant pleural effusions, cell wax block detection also has important reference value.
Regarding whether patients with early surgical resection of NSCLC need genetic testing, Professor Zhang Zheng believes that genetic testing should be routinely performed in such patients after surgery to guide subsequent systemic treatment. Although large Panel genetic testing is recommended, factors such as the patient's economic conditions, access to medications, and underlying disease should be considered when selecting a genetic testing package.
brief summary
The "Guidelines for Molecular Pathology Testing" mentions that the detection should take into account the timeliness and the number of targeted genes, and after assessing the quality of the specimens available for testing and the applicable detection methods, comprehensively consider the patient's visit time and disease progress, and select the appropriate detection strategy for the patients who are initially tested and retested, so as to provide the greatest help for clinical treatment decisions. In addition, the Guidelines for Molecular Pathology Detection also put forward emphasis and suggestions for indoor and outdoor quality control and communication between multidisciplinary teams (pathologists, clinicians, etc.). In short, NSCLC's molecular pathology detection should pay attention to standardized application, in order to develop an individualized diagnosis and treatment plan for advanced patients and escort them on the road to anti-cancer.
*Experts are ranked in no particular order
Expert Profiles
Professor Zhang Zheng
Director of the Department of Oncology, Luotian County People's Hospital, Deputy Chief Physician
ESCO Director, Deputy Chief Physician of Radiation Oncology
Member of radiation therapy committee of Hubei Anti-Cancer Association
Member of the Molecular Targeted Therapy Committee of Hubei Anti-Cancer Association
Standing Committee Member of Southeast Hubei Anti-Cancer Alliance
Vice Chairman of the Oncology Committee of Huanggang Medical Association
Standing Committee Member of Radiation Oncology Committee of Huanggang Medical Association
Professor Lu Dehong
Director of the First Department of Oncology, Changtu County Central Hospital, Chief Physician
Member of the Tumor Prevention and Control Committee of Liaoning Preventive Medicine Association
Member of the Lung Cancer Committee of Liaoning Life Sciences Society
Member of gastrointestinal branch of Liaoning Life Science Society
Member of Liaoning Life Science Cancer Support and Palliative Care Society
Member of Liaoning Society of Life Science Cancer Psychology and Treatment
bibliography:
Ying Jianming, Shi Xiaohua et al. Clinical Practice Guidelines for Molecular Pathology Detection of Non-Small Cell Lung Cancer (2021 Edition). Chinese Journal of Pathology, 2021, 50(4): 323-332.
[2] Chen J, Yang H, Teo A, et al. Genomic lanscape of lung adenocarcinoma in East Asians[J]. Nat Genet, 2020, 52(2):177-186.
Approval number: CN-91309 Expiration Date: 2023-3-16
The interviews/authors/publications of this article are supported by AstraZeneca and are intended for healthcare professionals only
Disclaimer: The interviews/authors/publications of this article are supported by AstraZeneca and are intended for healthcare professionals only
*This article is only used to provide scientific information to medical personnel and does not represent the views of this platform