Do cancer patients need genetic testing?

Do cancer patients need genetic testing?

Do cancer patients need genetic testing?  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.

The heterogeneity between tumor and tumor as well as 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, and so on. Tumor heterogeneity can hinder correct tumor treatment.

If the treatment is only focused on a small number of specific cells, it will easily lead to tumor recurrence. Usually, because of the heterogeneity of the tumor, the treatment of one receptor on 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 leads to the difficulty of tumor treatment.

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.

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 chemotherapeutic 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 progressing complex drug resistance, and provide guidance programs for further adjustment of medication.

Frequently Asked Questions Q&A of Tumor Genetic Testing

01 How is genetic testing applied in tumor treatment?

The main applications of genetic testing in tumor treatment are as follows:

1) Detection of tumor genetic susceptibility genes. The occurrence and development of tumors are closely related to heredity. Many gene mutations are inherited in the family. People who carry these mutations have a higher risk of developing tumors. 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 patient’s tumor tissue DNA and whole blood DNA to discover potential gene mutations, and looking for targeted drug therapies through current guidelines and drug development, such as non-small cells with EGFR mutations At present, lung cancer patients can 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 TKI-resistant EGFR T790M mutations can use third-generation osimertinib for subsequent treatment. Patients benefit.

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

02 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.;
• Targeted drugs for ALK gene mutations include crizotinib, ceritinib, loratinib, etc.;
• The targeted drug for KRAS gene mutation is Selumetinib+Docetaxel;
• The targeted drugs for BRAF gene mutations are Vemurafenib, Dabrafenib, etc.;
• The targeted drug for ROS1 gene mutation is 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.

03 Why use different treatment methods 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 a tumor at 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, and internal competitive pressure, the gene mutations of tumors will randomly undergo multiple mutations.

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 it can be different from disease to disease, which can bring the greatest benefit to patients.

04 What is early tumor screening? What does it do?

According to the definition of the US Centers for Disease Control and Prevention, early tumor screening refers to “checking the body for the presence of cancer when there are no symptoms.” Modern medicine has very limited treatment methods for patients with advanced tumors. The real way for tumors to get twice the result with half the effort is “early diagnosis and early treatment.” Most tumors can basically be cured if they are diagnosed early and undergo standardized treatment and health management.

Survival data released by an authoritative cancer hospital showed that the five-year survival rate of patients with early cervical cancer and colorectal cancer after standardized treatment can reach more than 90%; early breast cancer can even reach more than 97%. The key populations who need early tumor screening include: 45 years of age or older; family history of tumors (close relatives within 3 generations have a history of cancer); long-term exposure to hazardous substances (dust, benzene, lead, etc.) of the nature of work; patients with chronic diseases (pre-cancers of various types) Lesions, etc.), etc.

05 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 the purpose of treatment and monitoring of tumor 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 selected first. 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 specimens 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 advantages of using blood ctDNA for biopsy were mentioned: compared with conventional tissue biopsy. The advantages of invasiveness, good patient compliance, low heterogeneity, and reproducibility of materials, have great advantages in targeted drug companion diagnosis.

The recommended order of sample pros and cons is:

Tissue specimens obtained from new surgery or puncture>tissue specimens within 1-2 years>new blood specimens>old tissue specimens more than 2 years old.

06 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 certain 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.

07 After the tumor has been treated for a period of time, is it necessary to perform 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 performed to find out whether there are new gene mutations, and then new treatment methods can be adopted.

08 When using immune checkpoint inhibitors, such as PD-1 and PD-L1, why should genetic testing be done?

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 the use of 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 amplification may use immune checkpoint inhibitors, which may cause tumors to progress. Therefore, it is very meaningful to do genetic testing before choosing immune checkpoint inhibitor therapy.

09 A gene mutation is detected in a cancer patient. 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 tumorigenesis have been confirmed, and there are no targeted drugs currently on the market.

(source:internet, reference only)

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