Liquid biopsy in the diagnosis of lung cancer

When cells die, certain cellular components are released into the bloodstream. Cancerous tumors also release genetic material into the bloodstream. Based on this principle, liquid biopsies perform analysis and extraction of circulating DNA in blood samples, blood samples find out ctDNA of tumor cells based on EGFR gene mutations. Thus, the test sample of the liquid biopsy is not the cells or tissues taken directly from the cancerous tumor, but the patient's blood sample.
Currently, the most commonly used treatment method for non-small cell lung cancer patients with EGFR mutations is the use of small molecule drugs, tyrosine kinase inhibitors. In addition to testing for EGFR mutations on samples of cells, lung tumor tissue, or metastatic lesions, liquid biopsies also detect tumor free DNA without the need for complex biopsies.
Up to now, leading experts in the field have said that, although liquid biopsy has not completely replaced tissue biopsy in the diagnosis of lung cancer, it has also achieved significant significance. Liquid biopsy will be indicated instead of tissue biopsy in some cases.
For example, a biopsy of lung tumor tissue detects an EGFR mutation, but there is not enough DNA left to perform a screening analysis. If the tissue is biopsied again, this will be painful for the patient. At this time, a liquid biopsy will be indicated, analyzing the EGFR mutation results from the blood sample. The results of liquid biopsy and tissue biopsy in this case were similar.

However, the sensitivity of liquid biopsy in detecting EGFR mutations is not high, only about 70-80%, so liquid biopsy is not effective in diagnosing early lung cancer.
In addition, liquid biopsy test is also used in evaluating treatment effectiveness and checking metastasis. In many cases, patients on long-term tyrosine kinase inhibitors develop drug resistance. If tissue biopsies are performed, analyze only for the cause of resistance at certain sites. This may miss resistance gene mutations in other sites or regions. Meanwhile, liquid biopsy detects EGFR mutations, evaluates the heterogeneity of tumor lesions, and finds resistance mutations more comprehensively.
With targeted therapy for lung cancer patients, especially EGFR mutation-positive adenocarcinoma, liquid biopsy is indicated in each stage of the disease. Patients reduce pain, also give faster and more accurate results for mutations and drug resistance.

Currently, liquid biopsy test has been performed in many hospitals, on the new generation genetic analysis system. More and more patients are accessing and using liquid biopsies, a test of tumor-free DNA in the blood. Even so, there is little controversy about the benefit of repeating these tests in targeted therapy.

Patients with non-small cell lung cancer are prescribed liquid biopsies to monitor response to disease treatment. Many recent studies show that liquid biopsies in cured patients can predict the risk of disease recurrence at that time or in the future. Therefore, doctors hope to apply liquid biopsy to evaluate residual disease after treatment.
For patients with adenocarcinoma type, liquid biopsy helps to detect ROS1 and ALK gene rearrangements, BRAF, MET gene mutations. Therefore, liquid biopsy may be indicated instead or confirmed by tissue biopsy.

Although there is some controversy about the effectiveness of the liquid biopsy test in the diagnosis of lung cancer, its role cannot be denied. The test is painless, gives quick results and is highly accurate.
Research results have proven, testing for genetic mutations from tumor free DNA in the blood gives positive results with high reliability. False negatives can happen, but the rate of false positives is very low.

Initially, the tumor lesions developed uniformly, so the tissue biopsy results were highly reliable and comprehensively evaluated. However, in the disease stage, due to drug resistance, tumor lesions develop heterogeneously. Liquid biopsies now comprehensively evaluate more sites in the body, increasing the chance of detecting mutations.
Liquid biopsy has the disadvantage of inaccurate test results if: the sample is small, the tumor DNA circulating in the blood is too small. Therefore, liquid biopsy still cannot completely replace tissue biopsy in the diagnosis of lung cancer.
Moreover, this test technique is not popular in Vietnam, the cost of testing is also much higher than that of traditional tissue biopsies. Liquid biopsies still receive the attention and research of the international and Vietnamese medical profession, in an effort to prevent and defeat the evil lung cancer.
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