Cancer: biomarkers are revolutionizing cancer care

What is a circulating biomarker?

It is most frequently a cancerous cell (CTC) or circulating tumor DNA (ctDNA) present in the blood and stemming from a tumor. CtDNA is DNA released by the tumor cells when they become damaged and is found in the bloodstream.

As for CTCs, they are cells that detach from a tumor and enter the blood stream. They can migrate to other organs and lead to the development of metastases.

These biomarkers circulate in patients’ blood and are therefore accessible using a blood test, a simple medical procedure which is fast, relatively painless and economical.

What do circulating biomarkers contribute to the fight against cancer?

They provide valuable information on certain cancers that are not always easy to biopsy, as shown by Gudrun Schleiermacher, pediatrician at Institut Curie, for neuroblastomas. In this tumor affecting young children, analysis of the ctDNA seems to be a substitute for establishing the neuroblastoma’s genomic profile in cases where access to the tumor itself is impossible or to monitor its development to avoid repeated samplings.

Circulating biomarkers facilitate the choice of a targeted therapy. This blood analysis is sometimes referred to as “liquid biopsy.” A variety of studies conducted in recent years, in particular at Institut Curie, have shown that tumor biopsies can reasonably be replaced by the analysis of circulating tumor DNA to look for mutations that can be treated using targeted therapies. The “liquid biopsy” approach is now recognized as a standard in certain situations, particularly metastatic lung cancers.

We have also shown in metastatic breast cancers that the CTC rate is a major factor for the prognosis: the higher the rate of CTCs, the poorer the prognosis. Other than encouraging cancer to spread in the body, these tumor cells circulating in the blood encourage the occurrence of thrombosis (phlebitis, pulmonary embolism) in these patients.

In patients with non-small cell lung cancer, uveal melanoma or another type of colon cancer, the rate of ctDNA seems to be a good indicator of the response to new immunotherapy treatments. In addition, it is closely linked to the size of the tumor. Furthermore, if the ctDNA can no longer be detected in a patient, the patient has a lasting response to the treatment. We plan to conduct clinical trials shortly, where the measurement of ctDNA via a blood test may be an addition to or replacement of radiological scan tests.

In the long term, we also hope that these biomarkers will help detect certain cancers more quickly and allow us to monitor patients undergoing treatment.

What is the expertise of Institut Curie in this field?

We have been working on this for over 20 years. The proximity between the basic research laboratories, the geneticists who use the detection and analysis techniques, and the clinicians, who allow us, through the participation of a large number of patients, to conduct important studies, has enabled Institut Curie to become a world leader in this field.

Will there come a time when tissue biopsy is no longer needed?

This is already the case for certain indications, and the trend will certainly continue for other cancers. But liquid biopsy will never fully replace a tissue biopsy, which, for example, allows us to study a tumor’s relationship with neighboring tissues – in other words, its microenvironment.

François Clément-Bidard is a medical oncologist at Institut Curie, professor of medicine at the University of Versailles-Saint Quentin-en-Yvelines, and a researcher specializing in circulating biomarkers.