Imagine this scenario: a blood sample is used to diagnose certain kinds of solid cancers. It can also monitor the amount of cancer in a patient’s body, and even one's responses to treatment. Now, researchers at Stanford University School of Medicine have found a way to turn this scenario into reality.
Previous versions of the approach, which rely on monitoring levels of tumor DNA circulating in the blood, have required cumbersome and tedious steps to customize it to each patient. They also have not been sensitive enough.
The researchers' new approach, published in a paper in Nature Medicine, is very specific and sensitive and it is expected to be broadly applicable to many types of cancers. In fact, the researchers accurately identified about 50 percent of people in the study with stage-1 lung cancer and all patients whose cancers were more advanced.
The researchers’ technique, which they named CAPP-Seq, for Cancer Personalized Profiling by deep Sequencing, is so sensitive that it can detect just one molecule of tumor DNA in a sea of 10,000 healthy DNA molecules in the blood.
Screening Healthy People
While the researchers concentrated on patients with non-small-cell lung cancer (which includes most lung cancers, including adenocarcinomas, squamous cell carcinoma and large cell carcinoma), the approach is expected to be broadly applicable to many different solid tumors throughout the body.
According to the paper, it is also conceivable that it could be used to track the progress of a previously diagnosed patient, as well as to screen healthy or at-risk populations.
Dr. Maximilian Diehn, Ph.D., an assistant professor of radiation oncology at Stanford, told Healthline, "The blood test that we have developed for lung cancer could be adapted to nearly any cancer. We are starting to work on establishing it in the clinical lab here at Stanford...Currently, after a patient completes standard treatment for cancer it is often difficult to tell if all of the cancer cells have been eliminated. Patients therefore need to be followed with repeated scans. We're hopeful that our blood test will help to identify patients who still have cancer left in their bodies at the end of treatment. If so, it is possible that those patients could receive more treatment and increase their chances for a cure."
Liquid Biopsy for Lung Cancer
Also speaking to Healthline, Dr. Ash Alizadeh, a hematologist and oncologist who was also involved in the study, agreed with Diehn. “One of the most difficult things we struggle with, is how advanced the diseases of our patients are when they show up to see us and when we are seeing these patients for treatment, how long it takes before we are able to determine if they are having a response to the treatment."
Alizadeh continued, "The idea for this test is to get access to the tumor through the blood, relatively noninvasively compared to doing a biopsy. The current study focuses on taking solid tumors, which is the majority of cancer, and transforming them to liquid tumors by looking at what all cells do, which is why they die to release their DNA. We look in the blood for evidence of that DNA as a magnifying glass for what's going on in the tumor."
Emphasizing that the test is a liquid biopsy for lung cancer, which enables one to measure the presence or absence of lung cancer as well as the amount of lung cancer, and to monitor for it very accurately, Alizadeh said, "It's relatively inexpensive, and it doesn't involve getting scans. We see pretty striking results very early during the course of treatment. We are now starting to monitor it for lymphomas, cancer of the esophagus, pancreas, breast, and colon cancer."
Each Cancer Is Genetically Different
Noting that each cancer tends to be genetically different for different patients, Alizadeh said that although sets of mutations can be shared among patients with a given cancer, the researchers looked for which genes are most commonly altered, and used computational approaches to identify the genetic architecture of the cancer. That allowed us to identify the part of the genome that would be best to identify and track the disease.”
Researchers expect CAPP-Seq to also serve as a prognostic tool. The technique detected small levels of circulating tumor DNA in one patient who was thought to have been successfully treated for the disease. However, that patient experienced disease recurrence and died.
The researchers are designing clinical trials to see if CAPP-Seq can improve patient outcomes and decrease costs.