Using blood, saliva, urine to detect cancer: Scientists holy grail
Testing for cancer in blood, urine or even saliva: That approach has been called the “holy grail” for diagnosing the second leading cause of death in the world, and it has been fueling an area of research that continues to raise eyebrows and questions.
Doctors can diagnosis cancers in a number of ways, including taking biopsies of tissue where a suspected tumor might be; imaging tests such as X-rays, ultrasounds or MRIs; and screening tests such as endoscopies or colonoscopies.
Yet some of those approaches can be uncomfortable for patients or may come with hefty medical bills, among other potential downsides.
For the future, many cancer researchers are exploring whether a cancer test could involve only collecting and analyzing a sample of your blood, saliva or urine so that it’s noninvasive, cheaper and more appealing to patients — especially when trying to diagnose cancer early.
These bodily fluids or liquid biopsies “have the potential to help clinicians screen for disease, stratify patients to the best treatment, and monitor treatment response and development of resistance,” the American Association for Cancer Research says.
The science behind detecting signs of cancer in liquid biopsies — and how that could change the patient experience and public health as a whole — remains in the early, experimental stages but has spurred some excitement.
Audience members whispered amongst themselves in a crowded conference room at the Georgia World Congress Center in Atlanta on Tuesday during the American Association for Cancer Research annual meeting, where cancer researchers and other medical professionals gathered to watch a panel of scientists present the latest data on using liquid biopsies to detect cancer.
Some attendees held their phones in the air to take photos of the presentation.
If liquid biopsies help detect cancer early, that would be beneficial — as the earlier cancer is detected, the better chances of survival — but much more research is needed, said Nickolas Papadopoulos, a professor of oncology and pathology at the Johns Hopkins Kimmel Cancer Center in Baltimore, who presented as part of that panel.
With detection, “it’s a difference of thinking proactively rather than reactively to this disease,” he said.
Within the current body of liquid biopsy research, most studies seem to have focused on blood testing. There have been developments in creating blood tests to detect early stages of colorectal cancer and breast cancer, among others.
Still, this evolving research has some limitations. In general, cancer-screening tests can come with the risks of providing false positive or false negative results, overdiagnosis or even unnecessary treatments, all limitations to which blood tests could fall victim.
Overtreatment also can be a risk if a test detects a cancer that turns out to be slow-growing and therefore possibly harmless.
For instance, 1 in 3 women with breast cancer detected by a mammogram may be treated unnecessarily, because their screening tests found tumors that are slow-growing, according to a study published in the Annals of Internal Medicine in 2017.
On the other hand, finding cancer in an easy-to-collect blood test could improve survival rates when cancer is detected early and could be favorable among patients.
Being able to detect cancer from a simple blood draw compared with more invasive biopsies has been called the “holy grail,” not only for physicians but also for patients, said Medha Deoras-Sutliff, a two-time breast cancer survivor and executive director of The EHE Foundation, a nonprofit that focuses on a rare type of vascular tumor called epithelioid hemangioendothelioma.
Sutliff was first diagnosed with breast cancer 26 years ago, at the age of 27, after she told her primary care physician about a lump in her breast. She underwent a needle biopsy, during which a needle was forced into her breast at the site of the lump in order to pull out samples of it.
“Within a few minutes, they were able to look at it, and I got an answer it was benign,” said Sutliff, a graduate of the AACR Scientist-Survivor program.
“I thought that was OK, but we talked to a few other medical providers, and they thought, ‘Well, you can also get it removed, and you don’t have to think about it again,’ ” she said.
“I did remove it, and on examination after my surgery, they found, in another area of that lump, some suspicious cells. So that to me is how with biopsies, traditional biopsies, they pull sections from a certain area, and that’s it. But does that mean that the whole area of suspicion is uniform?
Well, we know that’s not true,” she said. “Cancer is not the same in each patient and even within each tumor. A biopsy only looks at one specific area of a suspected tumor.”
Sutliff continued to monitor her breasts, and when she was 36, physicians noticed something suspicious on her mammogram.
This time, “I had to do a core needle biopsy,” she said. “You lay flat on a table, and you’re on your stomach, and your breast is placed in a hole, and your table is raised.
The radiologist is under you, and you’re given a local anesthetic, and a hollow needle is guided into the breast.”
Her biopsy showed that she had breast cancer again, but it was in its early stages, and after treatment, Sutliff quickly recovered. However, the biopsies for both of her cancer diagnoses were “difficult,” she said.
If the future holds a simple blood test that could take the place of more invasive biopsies for some patients, that would be beneficial, Sutliff said.
“That holy grail is that blood draw will detect cancer in your blood, be able to determine where exactly that cancer may be in the body and hopefully tell us whether that cancer requires treatment,” she said.
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