liquid biopsy를 통한 암감지

https://medicalxpress.com/news/2020-06-blood-cancer-sensitive-current-methods.html

The technique uses personalized genetic testing of a patient's tumor to search blood samples for hundreds of different genetic mutations in circulating tumor DNA (ctDNA); DNA released by cancer cells into the bloodstream.

Combined with new methods to analyze this data to remove background noise and enhance the signal, the team was able to reach a level of sensitivity that in some cases could find one mutant DNA molecule among a million pieces of DNA—approximately ten times more sensitive than previous methods.

"Personalized tests that can detect if cancer is still present, or find it early if it is returning, are now being tested in clinical trials," 

Detecting ctDNA in blood samples is what is known as a liquid biopsy. It allows doctors to find out more about a patient's cancer without the need for invasive surgery. The technique is important for monitoring cancer patients, particularly after they've received treatment, as it can be an indicator of whether the treatment was successful and if the patient might relapse. In some situations, other types of tests can be used to detect some cancers before they display any symptoms or show up on a scan.

Currently, the sensitivity of the methods depends on having a high enough number of mutant pieces of DNA, either relative to background DNA or in absolute numbers. When the amount of ctDNA is low, a test can produce a negative result even if a patient has residual cancer in their body that could lead to relapse.

A single tumor will contain many different mutations that caused the cancer to form. While some of them are commonly known across certain cancer types, such as EGFR in lung cancer, the overall set of mutations for a tumor varies from person to person. By analyzing the genetic makeup of an individual's tumor and targeting a set of mutations in a personalized way, liquid biopsies to monitor cancer can become much more sensitive.

Until recently, these personalized liquid biopsies have searched for around 10 to 20 mutations in the blood and up to around 100 at most. In the material from a tube of blood, these would be able to detect ctDNA to levels on the range of one mutant molecule among 30,000 pieces of DNA.

The researchers describe traditional liquid biopsies as like looking for a needle in a haystack. This new approach of using personalized genetic profiles to search for many different mutations rather than just one, increases the number of 'needles' that can be found, making chances of success more likely.

They also say the "haystack" itself could be made smaller; as the methods developed for this research could mean that smaller and smaller amounts of blood could be required for the test to still work. Eventually, this could lead to tests that would require only a pinprick of blood—a procedure that patients could perform at home—that would then be sent to a lab for analysis. 

 

정확한 방법은 논문을 봐야겠다. 

 

reference

Jonathan C. M. Wan et al. ctDNA monitoring using patient-specific sequencing and integration of variant reads, Science Translational Medicine (2020). DOI: 10.1126/scitranslmed.aaz8084