Cancer’s genetic fingerprints may lurk in people’s blood long before they find out about the disease.
It’s possible to spot tumor DNA more than three years before a person is diagnosed with cancer, researchers report May 22 in Cancer Discovery. “We were shocked that we could find DNA,” says Yuxuan Wang, an oncologist and cancer researcher at Johns Hopkins University School of Medicine.
The findings suggest that hunting for these telltale traces using highly sensitive and accurate technology could be a powerful tool in early cancer screening efforts. It could one day help doctors detect cancers before any other signs or symptoms of the disease appear, she says. Even a diagnosis that’s a few months earlier than usual might mean more treatment options for patients. And a yearslong head start could be lifesaving. “It would dramatically change outcomes for our patients,” Wang says.
Scientists have known for years that tumor cells can shed DNA fragments into the bloodstream. But finding these fragments early in the disease’s progression is “like looking for a needle in a haystack,” Wang says. That’s because newly formed tumors are tiny and shed just infinitesimal amounts of DNA into the bloodstream.
Her team wanted to find out just how early it could spy this DNA in the blood. The researchers relied on samples collected during the 1980s–1990s in a study that has been tracking participants’ health for decades. They analyzed samples from 26 people who were diagnosed with cancer within the six months after the blood draw.
Blood from eight of the 26 study participants carried genetic signatures of cancer, lab tests revealed. That meant the team could spot cancer months before it was diagnosed. But was it possible to detect the disease even earlier? To find out, Wang’s team tapped into blood samples collected from participants more than three years prior to their cancer diagnosis.
The researchers used a technique called whole genome sequencing that let them spell out the individual letters that make up DNA. The team was able to pick out hallmarks of cancer DNA, alterations in the human genome that are cancer-specific. These were present at such low levels that the other lab tests would have missed them.
It wasn’t a given that the team would be able to detect cancer in those early samples. Not only were they roughly 40 years old and stored in tubes not designed to preserve DNA, but the team had only about a teaspoon of plasma, the cell-free portion of blood, to work with per sample. With larger and better-preserved samples, it’s possible that the genetic tests could be even more sensitive.
The fact that Wang’s team could detect cancer so early in the samples is “pretty provocative,” says William Grady, a gastroenterologist who studies and treats colon cancer at Fred Hutchinson Cancer Center in Seattle. He can imagine a Star Trek–style future where patients with tumor DNA in their blood are given some sort of “therapy that would basically eliminate those precancers.”
That day is probably still years away, Grady says. In the meantime, he’d like to see the results validated in a larger population of people — something Wang’s team is currently working on. The current study was a proof of concept, she says.
“The results are promising enough that we’re going to go back and look at more patients.”
English (US) ·