according to a new report.
The blood test focuses on circulating tumor DNA (ctDNA). By sequencing the complete genome of ctDNA, researchers can learn about the different metastases spread throughout the body.
“A key goal in cancer research is to better understand metastatic cancer in each affected person so we can select the best treatments and avoid giving toxic therapies to people who will not derive benefit,” senior author Alexander Wyatt, MD, DPhil, assistant professor of genitourinary cancer genomics at the University of British Columbia, Vancouver, and senior research scientist at the Vancouver Prostate Center, told this news organization.
“However, biopsies of metastatic cancer are rarely performed since they are invasive and have risks of complications,” he said. “In the past, this major barrier has prevented the widespread study of metastatic cancer and progress to better treatment of this lethal disease.”
The study was published in Nature.
Test methods
Blood-based biopsy technology, also known as “liquid biopsy,” has emerged as a tool for clinical cancer genotyping and longitudinal disease monitoring. Tests that use ctDNA have begun to influence the clinical management of people with cancer, the study authors wrote, though the full potential for understanding metastatic cancer biology hasn’t yet been unlocked.
Dr. Wyatt and colleagues analyzed serial plasma and synchronous metastases in patients with aggressive, treatment-resistant prostate cancer through deep whole-genome sequencing, which allows for a comprehensive assessment of every part of the genetic code within the cancer cells.
The researchers assessed all classes of genomic alterations and found that ctDNA contains multiple dominant populations, indicating that most people with metastatic cancer have different metastases spread around the body. They found that the whole-genome sequencing process provides a host of information about these different metastases.
The research team used newly developed computer programs to provide information about the genetic makeup of each cancer population, which can tell researchers about a person’s overall disease rather than about one metastatic tumor. In the future, this information could allow clinicians to make better decisions about managing a patient’s cancer.
The researchers studied multiple ctDNA samples collected over time to understand how a patient’s cancer evolved in response to treatment. They focused on inhibitors of the androgen receptor pathway. They found that current therapies for metastatic prostate cancer actively change the composition of cancer populations in the body and that treatment often selects for biologically aggressive cancer populations that underlie clinical resistance. This allowed them to pinpoint new genetic resistance mechanisms to the most common treatments for metastatic prostate cancer. The technique could be applied to other cancers as well.
The research team used nucleosome footprints in ctDNA to infer mRNA expression in metastases upon which biopsies were synchronously performed. They identified treatment-induced changes in androgen receptor transcription factor signaling activity. This means whole-genome sequencing of ctDNA can reveal the active processes occurring within cells, allowing clinicians to predict which treatments will be effective or ineffective in each patient.
“Our research significantly expands the breadth of cancer information that can be obtained from only a few drops of blood,” said Dr. Wyatt. “From a clinical perspective, this extra information can be used in new clinical trials that are testing strategies to direct cancer treatments only to those whose quality or whose length of life will be improved.”