When we get a blood test during a checkup, we usually learn about our blood sugar or cholesterol levels. But what if that same test could also reveal signs of cancer? A technology called liquid biopsy, which analyzes DNA circulating in the blood, is drawing growing attention in medicine and biotechnology.

Cells in the body constantly grow and die, releasing fragments of DNA into the bloodstream. These fragments are known as cell-free DNA, or cfDNA. In cancer patients, some of this DNA comes from cancer cells and is called circulating tumor DNA, or ctDNA, which carries information about genetic mutations that may have developed inside a tumor.

Unlike a traditional tissue biopsy, which requires removing tissue from a suspected tumor site, liquid biopsy only requires a blood draw. Because it can be repeated more easily, it may also be useful for continuously monitoring changes in a tumor and a patient's response to treatment.

Detecting cancer this way is not simple, however. Most DNA in the blood comes from normal cells, and the amount of ctDNA released by cancer cells can be extremely small, especially in early-stage cancer. Finding this faint signal among so much normal DNA is often compared to hearing a whisper in a noisy room.

A detected mutation also does not automatically confirm cancer. Technical errors during testing can appear to be real mutations, and some mutations may arise from causes unrelated to cancer. For this reason, results must be interpreted together with imaging tests, tissue biopsies, and a patient's symptoms and history.

Liquid biopsy is already used for some cancers to help guide treatment and monitor recurrence, and research into its use for early detection is actively underway. In the next article, we will explore how DNA extracted from blood is read and how next-generation sequencing (NGS) helps find these extremely faint cancer signals.

김효린 강남포스트 학생기자  webmaster@ignnews.kr

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