LIQUID BIOPSY

Bui Dac Chi,MDMedic Center

• The diagnosis of cancer has undergone a paradigm shift. No longer is cancer diagnosed only based on morphological parameters. More and more the diagnostic algorithm is supported by immunohistochemical and molecular alterations at the DNA, mRNAs, miRNAs and proteomic level. Multiple platforms and high throughput technological advances enable faster and cheaper analysis of all these as well as the whole genome.

• Liquid biopsy has the potential to provide information about cancers without invasive biopsy, using circulating biomarkers. These include proteins, RNA and DNA. They can be used in detection, diagnosis, monitoring and detection of recurrence. While protein-based tumour markers have been used in routine pathology for many years, the ability to detect mutations in circulating DNA is relatively new, and poised to enter clinical practice.

• Almost 150 years ago, T.R. Ashworth first described the presence of epithelial cells in the blood of a woman with metastatic breast cancer that were similar in appearance to her primary tumor cells. Indeed, many patients with a variety of solid tumors, including breast cancer, have detectable cancer cells circulating in the bloodstream, so-called circulating tumor cells (CTCs). CTCs represent a rare cell population in the blood, typically less than 10 cells/mL compared with 1 million WBCs/mL. However, the detection of CTCs within a routine blood specimen provides an opportunity to monitor cancer noninvasively, in essence a liquid biopsy.

• – Archives et manuscrits de la Bibliothèque de

l’Académie nationale de médecine • Archives organiques de l’Académie de médecine

– Prix de l'Académie » Acad. Med. - Prix - Buignet Prix Buignet » 1957 » n° 1. Mandel, P. Ensemble de travaux.

• Métais, P. ; Mandel, P., « Les acides nucléiques du plasma sanguin chez l’Homme », Comptes rendus des séances de la Société de biologie, 20 décembre 1947, Tome CXLII, p. 241 sq

• Exosomes are actively released vesicles (carrying RNA, DNA and protein) and can function as inter-cellular messengers.

• Three main approaches are being pursued: analysing circulating tumour DNA, examining whole tumour cells in the bloodstream and capturing small vesicles called exosomes that are ejected by tumours . And scientists have found that blood platelets(RNA) might be able to offer up cancer clues, too.

• Recent scientific advances in understanding circulating tumor cells, cell-free DNA/RNA, and exosomes in blood have laid a solid foundation for the development of routine molecular ‘liquid biopsies’. This approach provides non-invasive access to genetic information – somatic mutations, epigenetic changes, and differential expression – about the physiological conditions of our body and diseases. It opens a valuable avenue for cancer screening and monitoring. With the rapid development of highly sensitive and accurate technologies such as next-generation sequencing, molecular ‘liquid biopsies’ will quickly become a central piece in the future of precision medicine.

• LIQUID BIOPSIES ARE NON-INVASIVE BLOOD TESTS THAT DETECT

CIRCULATING TUMOUR CELLS (CTCS) AND FRAGMENTS OF TUMOUR DNA

THAT ARE SHED INTO THE BLOOD FROM THE PRIMARY TUMOUR AND

FROM METASTATIC SITES

CANCER AND SOMATIC MUTATIONS

• The majority of cancers arise after a series of somatic gene mutations that accumulate during an individual’s lifetime

• Identifying and understanding the somatic alterations in an individual’s tumor can be crucial in cancer diagnosis and in planning personalized cancer treatment, monitoring response to therapy, and identifying cancer recurrence. Moreover, as a tumor progresses, it continues to acquire additional alterations that can affect the response to therapeutic agents such as chemotherapy or targeted therapies.

• Distant metastases harbor unique genomic characteristics not detectable in the corresponding primary tumor of the same patient and metastases located at different sites show a considerable intrapatient heterogeneity. Thus, the mere analysis of the resected primary tumor alone (current standard practice in oncology) or, if possible, even reevaluation of tumor characteristics based on the biopsy of the most accessible metastasis may not reveal sufficient information for treatment decisions

Novel diagnostic biomarkers used in the clinic for various types of cancers and their targeted drug therapy.

WHAT IS A LIQUID BIOPSY?• The term “liquid biopsy” describes non-invasive,

highly sensitive and cost effective methods of isolating and detecting these cfDNA fragments, including circulating tumor DNA (ctDNA), from the plasma from patients diagnosed with cancer or from individuals who may have cancer. Liquid biopsies are thought to capture the entire tumor genome When liquid biopsy techniques are combined with deep sequencing technologies, a new set of tools is created that identify somatic genomic alterations in tumors.

Molecular diagnostic schema representing routine biological specimens and their molecular alterations.

POTENTIAL INDICATIONS FOR THE TEST

• Monitor residual disease in patients with known mutations in the primary tumor.

• · Monitor treatment efficacy in patients.• · Monitor disease progression and tumor evolution (i.e. development

of tumor resistance).• · Help the physician explore other options of treatment when the

patient is resistant to current therapies.• · Provide an alternative method for biopsy when tissue is difficult to

obtain or not available, or when the primary site of metastatic disease is unknown.

• · Provide an alternative method for biopsy when the quantity of tissue obtained in a biopsy sample is limited and traditional molecular genotyping is requested.

• · Provide prognostic information for some patients.

Analysis of CTCs

Yu et al. (2011) J Cell Biol

Is this the end of tissue biopsies?

“Tissue biopsy will remain the gold standard for the next couple of years. As scientific knowledge advances, researchers are learning more about the potential of liquid biopsies to detect mutations.

• At the moment, liquid biopsies are recommended when a tissue biopsy is difficult, such as in the case of lung cancer, or when the original site of the disease is unknown.

Liquid biopsies have a powerful role in helping patients get to the right treatment.

Conclusions• Molecular analysis of cancer is required to

optimise patient treatment• New methods such as next generation

sequencing show immense promise for the future

• Liquid biopsy is coming of age and will change practice – it will enable oncologists to use drugs intelligently to combat changes in individual cancers as they happen