Liquid Biopsies Are on the Way to Becoming a Good Alternative to Standard Tissue Biopsies for Stage 4 Cancer Treatment Planning

One of the greatest challenges encountered in cancer treatment is mutations in genetic structure that may vary between patients and even over time in the same patient. Many new-generation cancer drugs, called targeted drugs, target these mutations, and detecting them plays an important role in treatment decisions. Until now, critical information such as cancer mutations was obtained through conventional biopsies taken from tumor tissue using invasive methods; these mutations can now also be detected through noninvasive methods called liquid biopsy.

In recent years, the idea of diagnosing cancer and monitoring treatment progress noninvasively has gained prominence. Research led to the discovery of the liquid biopsy concept. Liquid biopsies may include circulating tumor cells (CTCs), circulating tumor DNA (ctDNAs), and molecules belonging to tumor cells such as fat, protein and RNA.

According to a study presented at the ASCO (American Society of Clinical Oncology) annual meeting in 2016, liquid biopsies may be an important option for selecting the most appropriate treatment for a patient. Blood samples from more than 15.000 patients with 50 different tumor types underwent genetic analysis [(Next-generation sequencing (NGS)]. The molecules sought in the genetic analysis were circulating tumor DNA fragments. Tumor tissue biopsies from the same patients were also genetically analyzed to test liquid biopsy reliability.

As a Result of the Analyses;

Genetic mutations supporting tumor growth (EGFR, BRAF, KRAS, ALK, RET) found in circulating tumor DNA fragments were also found at the same rate in biopsies from tumor tissues. Thus, instead of tumor biopsies that may physically burden the patient, a blood test was used to analyze the tumor’s genetic structure. In other words;

Liquid biopsies produce a portrait of the tumor’s entire genetic structure.

What Conveniences Can Liquid Biopsies Offer in Cancer Treatment?

• By monitoring genetic changes in the tumor through liquid biopsies, the most appropriate treatments can be administered to the patient.
• Treatment effectiveness can be determined through liquid biopsies. For example, if genetic analyses identify tumor cells that have developed drug resistance , administration of a different drug can begin.
• It may enable early cancer diagnosis. Changes in circulating tumor cells occur before the tumor reaches a clinically diagnosable level. Thus, cancer can be detected at an early stage through a simple blood test.
• Liquid biopsies provide information about all genetic changes in a tumor. Tumor tissue biopsies provide limited information because only a particular part of the tumor is taken.

Circulating tumor DNA fragments can be detected at very high rates in blood samples. However, the amounts of circulating tumor DNA fragments detected in brain cancers are very low. This is because the blood-brain barrier system prevents DNA fragments from passing into the bloodstream.

In summary, liquid biopsies play an important role in understanding a tumor’s genetic structure. Liquid biopsies aim to diagnose cancer at an early stage, select treatment appropriate for the patient and monitor treatment progress.