As an alternative to surgical biopsies, non-invasive tests such as liquid biopsy hold promise for screening cancer, and help in early detection of cancer. Liquid biopsy is a simple and non-invasive option to discover a range of information about a tumor through a simple blood sample. According to Cancer.org, other than skin cancer, prostate cancer is the most common cancer in American men and about 1 man in 9 will be diagnosed with this cancer during his lifetime. It is the second leading cause of cancer death in American men, behind lung cancer. A recent study published by researchers from the Karolinska Institute in Sweden has provided data on the ability of liquid biopsy to detect a range of tumor-associated genomic alterations in the blood of advanced prostate cancer patients.
This study, published in Genome Medicine opens many opportunities for further research and thus to speed up cancer treatment decisions. A combination of targeted and low-pass whole genome sequencing was performed on plasma cell-free DNA and matched white blood cell germline DNA in 364 blood samples from 217 metastatic prostate cancer patients.
Germline DNA was extracted from leftover EDTA blood. In addition, for 340 out of 364 circulating DNA (ctDNA)-analyzed blood samples, an additional blood sample was collected in a CellSave tube and shipped to the hospital for circulating tumor cells (CTC) enumeration within 72 hours on the FDA-cleared CellSearch platform.
Highlights of this study are:
- Circulating tumor DNA was detected in 86% of samples.
- Differences were measured in the levels of circulating tumor DNA that corresponded to how many treatments a patient had had
- The research team found that specific biomarkers, such as the androgen receptor have emerged as potential clinical predictors for prostate tumors
- The level of microsatellite instability (MSI) is also calculated in a subset of samples. This measure is increasingly used in the clinic to identify patients who are eligible for immunotherapies.
- About 3.8% of the cohort had high MSI based on the circulating DNA analysis.
The study concluded that "ctDNA profiling reflects the genomic landscape of metastatic prostate cancer tissue and may cost-efficiently provide somatic information in clinical trials designed to identify predictive biomarkers. However, intronic sequencing of the interrogated tumor suppressors challenges the ubiquitous focus on coding regions and is vital, together with profiling of synchronous white blood cells, to minimize erroneous assignments which in turn may confound results and impede true associations in clinical trials."