Liquid Biopsies are a Promising Method for Analyzing What Drives Cancers

WE HAVE KNOWN THAT cancers evolve since we first started treating them with chemotherapy in the 1940s — and that, after responding, they could become resistant to treatment.

When we developed better tools to analyze the genes in tumors over time, we were then able to discern specific abnormalities, particularly mutations, that led to treatment resistance. However, obtaining biopsies, especially repeatedly, is expensive, and not entirely safe. This has changed with liquid biopsies, a new way to look for those mutations from DNA released by tumor cells — through a simple blood draw and a genomic analysis of that sample. In this special issue of CURE, one of our articles highlights the importance of these new tests. Some are already approved to help make decisions about drugs that are specific for certain mutations. In the future, the ability to detect tumor DNA in the blood will allow researchers to study the evolution of tumors at the most detailed level. We are already aware of many genes that drive specific cancers during various stages of treatment, but we hope that ongoing analyses of mutational evolution over time will reveal more. Then, these could be targeted with a new generation of drugs that reverse resistance or could be given in combination with established drugs to make them work better and longer.

A study presented at the 2016 Annual Meeting of the American Society of Clinical Oncology looked at a genomic analysis of circulating tumor DNA in blood samples from more than 15,000 patients across multiple cancer types. According to researchers, a major finding of the study was that the patterns of mutation in circulating tumor DNA, found via liquid biopsy, matched up quite closely with those found through tissue analysis. This indicates the validity of liquid biopsy when compared with tissue biopsy. However, the matches were not perfect and some later evolutionary changes were missed.

The FDA has approved a couple of liquid biopsy tests to be used in diagnosing and characterizing lung cancer and melanoma, two cancer types with a number of known driver mutations. With these biopsies available in the clinic, we can now avoid the discomfort and the dangers of conducting tissue biopsies in difficult areas such as the lung or liver. Having knowledge of specific mutations is becoming increasingly more important in choosing the right treatments for individual patients, and this is starting to revolutionize clinical procedures. Liquid biopsies could contribute to our efficiency, turnaround time and decision-making processes as we pursue this important avenue.

There are some limitations, and for now most patients will still have to undergo tissue biopsies, but liquid biopsies hold a lot of promise when it comes to quickly, accurately and less invasively learning what drives a patient’s cancer.