Liquid biopsy
Liquid biopsy is becoming an increasingly important tool in cancer diagnostics, offering a less invasive and highly dynamic approach compared to traditional tissue biopsies. It involves testing blood, urine or other body fluids for genetic material such as circulating tumor DNA (ctDNA), tumor cells or exosomes that are released into the bloodstream from tumors.
Liquid biopsy can help diagnose cancer, select effective treatment, and monitor its effectiveness.
What constitutes a blood liquid biopsy sample? When a primary tumor is present in the body, some of its cells can break off and enter the bloodstream – they become circulating tumor cells (CTCs). Circulating and normal tumor cells secrete exosomes into the bloodstream, which carry bioactive molecules, including DNA. When tumor cells, both circulating and located in the primary tumor or its metastases, die (apoptosis or necrosis), circulating tumor DNA (ctDNA) is released from the cells into the bloodstream. When blood is drawn from a patient, ctDNA, CTCs and exosomes can be found in the sample, which become the basis for liquid biopsy studies.
Liquid biopsy tests can help in early cancer diagnosis, detection of metastases, population screening, and monitoring the course of the disease or response to therapy.
The amount of circulating tumor DNA (ctDNA) in the blood depends on the stage of the tumor at that time:
Why is liquid biopsy becoming increasingly important?
Liquid biopsy is much less invasive than traditional tissue biopsies, which typically require surgical procedures or needle aspiration to obtain tissue samples. This makes it a more accessible option, especially for patients who cannot undergo invasive procedures due to their condition or tumor location, or who avoid them due to potential complications.
Liquid biopsy can detect cancer earlier, sometimes even before symptoms appear. Detecting ctDNA or other tumor markers at an early stage could allow for earlier treatment, increasing the chances of successful treatment. It could also be used to screen high-risk patients, although this is still being investigated.
Liquid biopsy allows for real-time monitoring of how a cancer is responding to treatment. By regularly assessing changes in ctDNA levels or the emergence of new mutations, doctors can more dynamically adjust treatment plans, thereby preventing resistance before it becomes clinically significant.
After surgery or treatment, liquid biopsy can help detect minimal residual disease (MRD)—a small amount of cancer cells or DNA that may remain in the body and could cause a relapse. This can be an early warning sign of relapse and prompt further treatment.
Liquid biopsy can be used to identify specific genetic mutations, which can not only aid in diagnosis but also help determine the most effective treatment options. This is especially relevant for cancers with known mutations (such as EGFR mutations in non-small cell lung cancer) or to identify potential targets for precision medicine.
Over time, tumors can evolve and acquire new mutations that can lead to resistance to treatment. Liquid biopsy offers the ability to track this evolution by taking samples of the tumor's genetic material from the blood. This allows doctors to detect changes in the tumor's genetic profile that may require a change in treatment or an adjustment in the treatment strategy.
For many patients, liquid biopsy is a more convenient, faster, and less painful alternative to traditional biopsies. It can improve the overall patient experience, especially for those who need regular follow-up.
Sources
- Pascual J, Attard G, Bidard FC, et al. ESMO recommendations on the use of circulating tumour DNA assays for patients with cancer: a report from the ESMO Precision Medicine Working Group. Ann Oncol. 2022;33(8):750-768. doi:10.1016/j.annonc.2022.05.520
