Scientists are getting closer to developing blood tests that can detect cancer early, before patients show any symptoms of the disease.
One of those tests, called PanSeer, can detect five cancers up to four years earlier than current diagnostic methods, according to a study published Tuesday in the journal Nature Communications.
The test works by detecting small pieces of DNA that tumor cells release into the bloodstream. Researchers have been working on this type of DNA sequencing application for years, and the development takes the industry one step closer to using a blood test to diagnose cancer before it progresses to advanced stages, which are more difficult. to try.
“We are transforming the proof-of-concept stage into a commercial product that is robust, inexpensive and can be implemented in clinics,” said study co-author Kun Zhang, chair of the bioengineering department at the University of California, San Diego, who co Singlera Genomics, the company that designed PanSeer. At this point, however, the test is still years away from being used by doctors.
Dr. Eric Klein, urologist at the Cleveland Clinic’s Taussig Cancer Institute, called the findings “another validation, in addition to other published studies, that cancers release DNA fragments into the bloodstream that can be detected at low levels. levels. “
“The four-year prediction was incredible,” added Klein, who was not involved in the research.
In the study, Zhang and his team retroactively analyzed blood samples taken from 605 asymptomatic people, of whom 191 were later diagnosed with colorectal, esophageal, liver, lung, or stomach cancer using standard diagnostic methods, to see if they could detect the small pieces of DNA that would indicate cancer.
The researchers also tested the accuracy of PanSeer in plasma samples taken from 223 cancer patients, as well as 200 samples of healthy and tumor tissue. They determined that the test could detect cancer DNA in the blood of asymptomatic patients with 95 percent sensitivity, detecting signs of cancer up to four years earlier than current detection methods normally would. (The higher the sensitivity, the lower the probability of false negatives).
However, the test cannot distinguish which of the five types of cancer a patient has, based on DNA fragments, which means that additional tests would be needed to determine the specific type of cancer.
Zhang believes the technology is a clinical trial that is far from being approved for use in patients, but that means that a blood test that detects cancer at an early stage is still years away from being used in doctors’ offices. Even when it is, tests are unlikely to replace current screening methods for certain cancers, including mammograms, colonoscopies, and Pap tests, in the short term.
“At least initially, blood tests will not eliminate the need for routine screening tests that doctors currently recommend. They may eventually pass current tests, but not right away, “Klein said.” We also need to be careful that patients don’t think that because they’ve had a negative test, they have zero risk of cancer. “
Where the tests may be particularly helpful is in diagnosing certain types of cancer that are currently difficult to detect, including stomach and liver cancer.
“All of the screening tools that have been applied to these cancers have not been very effective, and that’s where this could be really helpful,” said Dr. Mark Roschewski, clinical director of the Lymphoid Malignancies Branch of the Center for Research in the Cancer from the National Cancer Institute, he told NBC News.
According to Roschewski, being able to create a test that produces 100 percent specificity, meaning there are no false positives, rather than 96 percent of PanSeer, is an important trait that any cancer blood test that hits the market should provide.
“People without disease need to test negative,” he said. “The last thing you want to do is take someone who is completely healthy and put them through a series of tests and the stress of being told they have cancer when they don’t.”
Roschewski also cautioned that just because cancer is detected at a very early stage, it cannot necessarily be treated at diagnosis, while other slow-growing cancers may not require treatment for years.
Klein noted that it’s also important for patients to understand that PanSeer and its competitors are first-generation tests that won’t always detect every type of cancer the tools are said to detect.
“But this is a validation that the approach has real substance, and as the understanding of technology advances, we will make a real impact on cancer mortality with this approach,” said Klein. “It is a fundamentally different technology, and a different way of looking for cancer than we have ever had in the past.”
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