By Matt McMillen
WebMD Health News
Reviewed by Hansa D. Bhargava, MD
March 28, 2017 -- Detecting cancer may be getting easier.
New kinds of tests that promise to be less invasive are beginning to exit the lab and enter the market -- with more under development.
By using blood, urine, and saliva, researchers hope these new tests may reduce the need for often painful, risky biopsies, a type of surgery to remove suspicious tissue for study.
The hunt for new ways to detect cancer has heated up in the past few years, as has investment in new tools and tests. In January, a San Francisco-based startup called Grail pledged to raise $1 billion to develop a blood test for early detection.
"Five years ago, there would not have been such a long list [of new and experimental tests]," says Peter Mazzone, MD, the director of the lung cancer program at the Cleveland Clinic's Respiratory Institute.
The discovery that cancer can be detected in certain biomarkers, like DNA, RNA, and proteins, is driving test development. Advances in technology over the past 5 to 10 years have allowed scientists to use those discoveries to create tools to diagnose cancers.
Already, at least three early cancer detection tests are on the market. The FDA approved Cologuard, which screens for colon cancer, in 2014. Oncimmune and Integrated Diagnostics have developed blood tests that help screen for lung cancer and are performed in the companies' federally certified laboratories. (FDA approval is not required for tests unless they are commercially marketed.)
Both tests involve sending a patient's blood sample to company laboratories for analysis. Both labs are Clinical Laboratory Improvement Amendments (CLIA) certified, meaning the companies can charge for performing tests in their labs and do not need FDA approval to do so.
Meanwhile, the Mayo Clinic and Exact Sciences Corp. recently announced a promising blood test for lung cancer based on Cologuard, also developed by Exact Sciences.
Early detection of cancer is an important key to treating and sometimes surviving it, experts agree.
But many cancers -- pancreatic and ovarian tumors, for instance -- often have no early symptoms, meaning diagnosis may come at a late stage. Meanwhile, other people have biopsies and unnecessary testing for what turns out not to be cancer -- harmless nodules in the lungs, for example.
"We don't want to harm people by doing a biopsy or by over-testing them," says Mazzone, who has researched breath and urine tests to ID lung cancer -- by far the leading cause of cancer death in the U.S. "That's an area where these breath, blood, and urine tests might help us."
Such tests would identify things like abnormal chemicals or chemical patterns that show that a disease is present, says Mazzone.
They may also help fine-tune existing methods of cancer detection. For example, lung CT scans often find small spots called lung nodules. About 99 times out of 100, the nodules are harmless, says Mazzone. But it can be hard to distinguish between harmless ones and those that signal an aggressive cancer.
"There are lots and lots of false positives," says Richard Schilsky, MD, chief medical officer at the American Society of Clinical Oncologists. "The challenge is to figure out which if any among these abnormalities actually is cancer."
So far this year, researchers have published numerous new developments in cancer testing. The research is in early stages, but it demonstrates the current push to develop new diagnostic methods:
- Researchers at Boston University identified more than 500 genes related to lung cancer found in the nose. By taking a nose swab, the genes may help researchers determine whether growths in the lung are malignant.
- At Massachusetts General Hospital, scientists developed a method of detecting cancer cells in the blood that could improve the early diagnosis and treatment of lung cancer.
- In South Korea, experts at the Ulsan National Institute of Science and Technology published a promising study showing that urine tests can identify cancer cells shed by tumors.
- Purdue University researchers discovered that high levels of certain proteins in the blood appear to indicate breast cancer. The blood test may be able to detect other cancers as well.
In early March, researchers at the University of California, San Diego, developed a blood test that not only detects cancer, but also finds where it is in the body.
The test identifies normal cells killed by a growing tumor. Those dead cells wind up in the bloodstream before they are flushed out of the body. Researchers traced those cells back to the part of the body they came from, such as the liver, the pancreas, the kidneys, and the lungs. In the study, researchers screened blood samples from people with and without cancer.
"Current blood tests are only used on people who already have been diagnosed, to see if cancer can still be detected in the blood after treatment," says bioengineering professor Kun Zhang, PhD. "We're working on early diagnosis."
One type of cancer he wants to target is pancreatic cancer. Right now, he says, a diagnosis usually means death within 2 years because it doesn't catch the disease in time to treat it successfully.
"Early diagnosis and intervention may provide a cure," he says.
Zhang says the next step is to test his research in the real world. He and his colleagues plan to collect blood samples from a large number of currently healthy people and then observe them over 2 to 3 years to see if his test accurately identifies those who develop cancer. Zhang can't say when this research will be completed.
Schilsky says that a good test is both sensitive and specific. By sensitive, he means that the test can pick up even very small amounts of whatever it's searching for, such as tumor DNA in the blood. Specific means that the test can accurately identify its target and distinguish it from the many other substances around it.
Proving a test is accurate is an early step in the development process. Next, developers must show that it works in the people it's meant for. A successful test for lung cancer, for example, must show that it can identify the disease in adults between ages 55 and 80 who smoked for 30 years -- a group known to be more likely to get the disease.
Schilsky says that it can take years to determine whether a test actually saves lives. In the case of an often aggressive cancer like lung cancer, it may take 5 years. Tests for cancers that often move more slowly, like colorectal cancer and breast cancer, may require about 15 years.
Not all cancers will kill you, and tests may eventually help doctors tell the difference between deadlier forms of the disease and cancers that are much less of a threat.
"Prostate cancer is the case study," says Schilsky. "You can detect lots of prostate cancer, but many of them will not become clinically significant. You would like to have a test that tells the doctor whether a particular cancer is going to behave badly."
Mazzone says the goal of a test is to help a doctor make the right decisions. "Sometimes even accurate tests don't lead to changes in decisions that go on to help patients. … People still die even though they got screened."
While these are exciting times for cancer researchers, Mazzone sounds a note of caution.
"No test is perfect. Every yes doesn't mean yes, and every no doesn't mean no. If a test is used inappropriately, it can cause harm. The medical and research communities have to assess these tests completely before widely using them."
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SOURCES: Peter Mazzone, MD, director, lung cancer program, Respiratory Institute, Cleveland Clinic. Richard Schilsky, MD, chief medical officer, American Society of Clinical Oncologists. Kun Zhang, PhD, professor of bioengineering, University of California, San Diego. EurekAlert: "Breakthrough discovery may make blood test feasible for detecting cancer," "Study finds biomarker for lung cancer detection in the nasal passages of smokers." Exact Sciences: News release. ScienceDaily: "Digital assay of circulating tumor cells may improve diagnosis, monitoring of liver cancer," "New blood test could help detect, locate cancer early on," "Urine-based biomarkers for early cancer screening test." Tech Crunch: "Grail is raising at least $1 billion to fund its early cancer screening test." U.S. Preventive Services Task Force: "Lung Cancer: Screening." International Journal of Molecular Sciences: "Clinical Advances in Molecular Biomarkers for Cancer Diagnosis and Therapy."
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