By Kelli Miller
WebMD Health News
Reviewed by Michael W. Smith, MD
Sept. 26, 2014 -- Spotting cancer early is key, but trying to do that -- often when there are no symptoms -- has been challenging.
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Still, more and more evidence suggests that all cancers have a signature, or even a scent, that can be detected early. Now, researchers worldwide are testing simpler methods to spot the subtle signs of:
Some tests are already available.
"During the past couple of decades, scientists have learned a great deal about the cellular and molecular changes that distinguish cancers from normal tissues," says Ted Gansler, MD. He's the director of medical content at the American Cancer Society. "Most professionals who follow the field of cancer screening and diagnosis are excited about the implication of this … in eventually reducing cancer deaths."
Here are a few cancer detection methods that experts say are worth watching.
Breath Tests for Cancer
Your breath can reveal many clues about your health, and not simply whether you brushed recently. The air that you breathe out has hundreds of different chemicals, called volatile organic compounds (VOCs).
Many studies have shown that exhaled breath from people with lung and breast cancers has a distinctly different panel of "odors" or VOCs compared to the breath of people without such cancers.
Detailed lab experiments and a robust knowledge of cancer's biochemistry helped fuel these findings. But some say you could also give a bit of credit to dogs.
Decades ago, there were a few word-of-mouth reports about dogs sniffing out cancer in their owners. Since then, "a growing number of scientific studies support the accuracy of dogs in detecting chemicals released by cancers," Gansler says. Those include colon, breast, bladder, ovary, prostate, and lung cancer, among others.
Today, clinical trials are underway to find out if breath sensors and artificial noses based on dog-sniffing research can accurately detect certain lung cancers.
Peter Mazzone, MD, MPH, is director of the lung cancer program at Cleveland Clinic Respiratory Institute. He has studied breath and urine tests for lung cancer with encouraging results. "Our results have shown around 85% accuracy in distinguishing those with cancer in high-risk patients," he says.
The tests are fairly simple and pose no risk, according to Mazzone. You just breathe out, and sensors in the equipment pick up your unique "breath print." The odors in the breath sample are captured by the system and change colors when exposed to specific chemicals.
"Easy detection is the key," says Hossein Borghaei, DO. He's the chief of thoracic medical oncology at Fox Chase Cancer Center in Philadelphia, where a lung cancer breath test clinical trial is being done. "Exhaled breath collection is cheap and can be applied to a wide population relatively quickly and at low cost."
Study co-author J. David Beatty, MD, says it's possible that checking for VOCs in women without obvious symptoms "will help find breast cancer earlier and result in improved outcomes from treatments." But he cautions that it's too early to consider such testing as a replacement for mammograms. Beatty is the medical director of the clinical and bioinformatics program at the Swedish Cancer Institute in Seattle.
Saliva Tests for Cancer
Breath odor aside, the mouth itself has long been considered a gateway to a person's health. Bacteria inside the mouth not only trigger cavities and gum disease -- they may also reveal certain cancers, including pancreatic cancer, which often goes undetected until it has progressed.
A simple swab of saliva might help better diagnose early pancreatic cancer. Research presented at the American Society of Microbiology annual conference in spring 2014 found people with pancreatic cancer have different types of bacteria in their saliva compared to those without cancer or those with different pancreatic diseases.
Michael Bouvet, MD, FACS, is co-director of the GI cancer unit at the University of California San Diego (UCSD) Moores Cancer Center. He's been involved in clinical trials of a saliva test for pancreatic cancer, and he hopes the research will lead to an easier way to track people at risk for pancreatic cancer.
"We're getting some results that look very promising," he says. "Our preliminary data has found that the saliva of patients with pancreatic cancer has lower levels of certain bacteria and higher levels of other ones."
Clinical trials have also been done or are underway to find out if saliva tests could be used to diagnose or detect someone's risk of oral cancer.
Blood, Stool Tests for Cancer
All cancers shed DNA into the bloodstream. Many different blood tests, or "liquid biopsies," are being developed to spot these genetic pieces, as well as proteins, tumor fragments, and other biomarkers, specifically linked to cancer.
"Much of the basic cancer research of the past few decades has focused on identifying the DNA, RNA, and protein changes that distinguish cancer cells from normal cells," Gansler says. "Technology has allowed scientists to detect these changes in samples of blood, urine, and feces."
Recent studies have found that circulating tumor DNA (ctDNA) was successfully detected in people with early-stage:
- Breast cancer
- Colorectal cancer
- Gastroesophageal cancer
- Pancreatic cancer
Some biomarker blood tests for cancer are already available.
Red blood cells and DNA changes related to colorectal cancer also shed into the GI tract as stool passes out of the body. Now, an easy-to-use test is available to detect these abnormal signs long before colorectal cancer changes show up in the bloodstream.
In August 2014, the FDA approved Cologuard, the first fecal DNA test. Current screening recommendations do not include the use of Cologuard, but experts say it expands the options available for colorectal cancer detection.
Imaging tests, such as mammography and CT scans, also play an important role in cancer diagnosis and tracking.
As technology improves and scientists learn more about the makeup of cancer, screening tests will continue to evolve to detect earlier and smaller cancers, even pre-cancers -- some that may never become life-threatening.
"It is important to develop methods that accurately predict which of these early cancers are genuinely serious, and which patients can safely avoid side effects of surgery, radiation, and/or chemotherapy," Gansler says.
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