Genetic testing and adjuvant cancer treatment

Do cancer patients need genetic testing?

The heterogeneity between tumor and tumor and the heterogeneity within a single tumor is one of the bottlenecks of current tumor treatment. Specifically, it includes individual heterogeneity, heterogeneity of different tumor cell types, heterogeneity within the same tumor cell, etc. Tumor heterogeneity can hinder correct tumor treatment. If the treatment only focuses on a small number of specific cells, it will easily lead to tumor recurrence. Usually, because of the heterogeneity of tumors, treatment for one receptor of the tumor often does not have a significant effect. At the same time, the heterogeneity of tumors is not only the presence of multiple tumor subclones, but also the heterogeneity of the tumor microenvironment, which makes tumor treatment difficult.

At present, tumor treatment has entered the era of individualized medical treatment of molecular targets, and tumor treatment has gradually changed from pathology-based to an era where pathology and driving genes jointly determine choices. The complexity of the tumorigenesis mechanism also reminds clinicians that if they can perform genetic testing and analysis before choosing therapeutic drugs, it is very important to guide the medication of treatment. Specifically, suitable targeted drugs can be accurately recommended for patient genotyping, the patient’s important variant genes can be analyzed, and medication tips for targeted drugs and chemotherapy drugs can be made. At the same time, some patients often have drug resistance problems during the treatment process, and there are many drug resistance mechanisms. Only when the cause of drug resistance can be determined can further treatment options be selected. Genetic testing can analyze the mechanisms and causes of drug resistance in patients with advanced drug resistance, and provide guidance for further adjustment of medication.

How is genetic testing applied in cancer treatment?

The current applications of genetic testing in tumor treatment mainly include the following three points:

(1) Detection of tumor genetic susceptibility genes. The occurrence and development of tumors are closely related to heredity. Many gene mutations will be inherited in the family. People who carry these mutations have a higher risk of cancer. Genetic testing can predict the risk of corresponding tumors and carry out active health management.

(2) Tumor screening is mainly liquid biopsy technology, through the sequencing of free DNA, to achieve early cancer screening. At present, genetic testing is more mature in tumor screening and cancer recurrence screening.

(3) Targeted drug therapy for tumors, by comparing the DNA of the patient’s tumor tissue with DNA from whole blood, discovering potential gene mutations, and looking for targeted drug treatments through current guidelines and drug development, such as non-small EGFR mutations. Patients with cell lung cancer can currently achieve continuous treatment of multiple generations of targeted drugs. First-generation and second-generation gefitinib are used for first-line treatment. For example, patients with EGFR T790M mutations with TKI resistance can use third-generation osimertinib for subsequent treatment. Benefit for patients.

(4) Genetic testing can also be used to detect tumor invasion and metastasis. Through genetic testing of metastases and in situ, it is necessary to find out whether there are key genes that drive tumors and whether there are corresponding targeted drug treatments.

Which genes are concerned about targeted therapy for lung cancer patients? What targeted drugs can be applied?

Targeted therapy for lung cancer is now mainly focused on EGFR, ALK, KRAS, BRAF, ROS1, MET, RET and HER2 genes. Targeted drugs for EGFR gene mutations include gefitinib, erlotinib, afatinib, etc.; ALK gene mutations target drugs for crizotinib, ceritinib, loratinib, etc.; KRAS gene mutations The targeted drugs for BRAF gene mutations are Selumetinib + docetaxel; the targeted drugs for BRAF gene mutations are Vemurafenib, Dabrafenib, etc.; the targeted drugs for ROS1 gene mutations are crizotinib; the targeted drugs for MET gene mutations are crizotinib and Capmatinib; the targeted drugs for RET gene mutations are Cabozantinib and Vandetanib; the targeted drugs for HER2 gene mutations are TKI single drugs such as afatinib or trastuzumab plus chemotherapy.

Why are there different treatments for the same tumor?

Tumor is a genetic disease. When one or more genes in a cell are mutated, it may cause tumors. Tumors are very different, even if it is the same site, the gene mutation site and type of the primary tumor are not the same. If the tumor has metastasized, the gene mutation information of the original tumor and the metastatic tumor may also be different. In addition, under the influence of environmental factors such as drugs, immune system, internal competitive pressure, and other environmental factors, tumor gene mutations will mutate randomly. Therefore, the disease of each tumor patient is different, and the disease of the same tumor patient will also progress.

With the continuous development and innovation of genomics and genetic testing technology, tools and foundations are provided for precision medicine. In the treatment of tumors, the same disease can be treated differently, and the disease can be different, which can bring the greatest benefit to patients.

Should tumor patients use tumor tissue or blood for genetic testing?

At present, there are two kinds of commonly used samples for genetic testing for treatment and monitoring of cancer patients, tumor tissue and blood. Taking tumor tissues into pathological sections for genetic testing, with high accuracy, is the gold standard for tumor genetic testing. Where conditions permit, tissue samples should be preferred. Not all gene mutations in cancer patients can be detected in the blood, especially in the early stages of the tumor, the positive detection rate is lower. However, for patients with advanced tumors, unable to obtain tissues, or tissue samples for a long time, consider using blood tests instead of tissues. In the "Current Status and Prospects of the Application of Liquid Biopsy in the Diagnosis and Treatment of Clinicopathological Related Tumors" published in the "Chinese Journal of Pathology" in December 2018, the application of blood ctDNA for biopsy detection was mentioned.

Advantages: Compared with conventional tissue biopsy, it has the advantages of non-invasiveness, good patient compliance, low heterogeneity, and repetitive material selection. It has great advantages in targeted drug companion diagnosis.

The recommended order of sample order is: tissue samples obtained from new surgery or puncture> tissue samples within 1-2 years> new blood samples> old tissue samples more than 2 years old.

How can I know whether my tumor will be passed on to my children? If the tumor is hereditary, how can children prevent and control the occurrence of tumors?

Tumor is a genetic disease. Due to the mutation of some genes, the growth is out of control, which leads to the occurrence of tumors. Certain gene mutations are hereditary. People with genetic susceptibility genes have a much higher risk of developing tumors than normal people. Tumors caused by genetic susceptibility genes account for 5-10% of all tumors. There are more than 20 kinds of tumors with obvious genetic predisposition, the more common ones include: ovarian cancer, breast cancer, colorectal cancer, pancreatic cancer, prostate cancer, gastric cancer, etc. Genetic susceptibility genes can be detected through germline genetic testing. If cancer patients are found to have genetic susceptibility genes, their children should be tested for related genes as soon as possible. For healthy people carrying genetic susceptibility genes, early treatment and health management can be carried out under the guidance of a doctor, which can effectively delay or even avoid the occurrence of tumors.

After the tumor has been treated for a period of time, does it need to undergo genetic testing again?

Genes in tumor tissues continue to mutate, and the mutation process is completely random. Effective treatments will affect the frequency of mutations and reduce the chance of harmful mutations. Therefore, after treatment for a period of time, in the case of drug resistance or disease progression, genetic testing can be carried out to find out whether there are new gene mutations, and then new treatment methods can be adopted.

Why use immune checkpoint inhibitors, such as PD-1 and PD-L1, also do genetic testing?

Tumor patients with high TMB (tumor mutation burden) benefit more from immune checkpoint inhibitors and are more suitable for treatment with immune checkpoint inhibitors. Patients with mutations in the PBRM1 and POLE genes will benefit more from immune checkpoint inhibitors. Tumor patients with JAK1, JAK2, BM2, HLA, STK11 and other gene mutations may be resistant to immune checkpoint inhibitors, so they need to be tested in advance. Patients with tumors with EGFR mutations and MDM2 amplifications, using immune checkpoint inhibitors, may cause tumors to progress. Therefore, it is meaningful to do genetic testing before choosing immune checkpoint inhibitor therapy.

Tumor patients have detected genetic mutations, is there a targeted drug that can be used?

There are many types of gene mutations, and it is not clear whether many mutations are related to the occurrence of tumors. Some gene mutations (such as P53 mutation, MYC amplification, etc.) related to tumor occurrence have been confirmed, and there are no targeted drugs on the market.

Source: Shanghai Chest Hospital, invasion and deletion.

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