A test designed to catch bits of cancer DNA in the blood of otherwise healthy people was launched recently by Pathway Genomics. The test is a first in “liquid biopsies,” blood sample tests that use gene sequencing technology to detect trace amounts of DNA mutations associated with various cancers.
The San Diego-based company says the test is the next big thing in medicine; for $699, you can purchase the test in the hopes that if the early biomarkers of cancer are present in your body, the screening will catch the disease long before it actually, well, turns into the disease. 
The test looks at 96 genetic markers associated with breast, ovarian, lung, colon, melanoma, and other major cancers, focusing on fairly well-understood mutations with established treatments. 
The launch raises the question of how much genetic information should be given to healthy people if there’s nothing to suggest the data could help them prevent developing the cancer.
There’s also no proof that the test actually works, nor has the Food and Drug Administration reviewed it. Yet, Pathway Genomics markets the test as a “cancer stethoscope.”
“The sensitivity of the test is very high and it can be used to potentially catch cancers at a much earlier stage,” says Pathway Genomics CEO Jim Plante.
“For any given test, the rate of false positives causing unnecessary alarm and false negatives that provide false security should be known,” said Dr. Keith Stewart, an oncologist who heads Mayo Clinic’s Center for Individualized Medicine.
The findings of the test could mean more patients lining up to get unnecessary MRIs in search of disease, and in the end, they could wind up putting themselves at further risk for cancer from exposure to the radiation from such scans.
“I am very reticent to believe a privately-funded personal genomics company’s claims when there is no peer-reviewed data to support their tests or technical approaches,” says Isaac Garcia-Murillas, an oncologist at the Institute of Cancer Research in London.
Garcia-Murillas has been developing a blood test that intended to calculate the risk of breast cancer relapse.
Plante says the test has been validated through tests on “hundreds of samples.” MIT Technology Review points out that it would take thousands of samples, many years, and millions of dollars to determine whether the test actually helps or hurts people.
Consumers looking to purchase the test, CancerIntercept, consult with a “telemedicine” doctor before they can order it. The company sends a “mobile phlebotomist” to the customer’s home to draw blood. Pathway Genomics also offers people a “subscription” that allows them to have their blood tested four times a year for the oh-so-low price of $1,196.
Antonio Regalado, senior editor for biomedicine at MIT Technology Review, writes that the subscription offer misleads consumers.
“I am not aware of any evidence, whatsoever, that frequent, repeated testing for cancer mutations has any benefit,” Regalado says.
He goes on to cite a Reuters article that discusses how, in 2010, Walgreen’s pulled the company’s genetic testing kits from its pharmacies after U.S. health regulators warned patients might take action without understanding the results.
Luis Diaz, of Johns Hopkins University, says that “there are three levels of errors: technical, biological background, and clinical context.” First, such testing can produce false positives.
Trying to catch cancer early makes it more likely that you will get a false-positive that is actually a “technical artifact” caused by the test. This could frighten people into believing they have cancer when they don’t.
Second, some “biological artifacts” and genetic mutations accumulate in people as they age, but they don’t mean they have cancer.
Third, if people start finding and treating cancers that will never kill them, it’s hugely financially-taxing.
MIT Technology Review noted in a 2014 article:
“Medicine has a precedent of handling predictive cancer tests poorly. Consider the PSA test. Millions of men have ended up getting treated for prostate cancers that ultimately wouldn’t have affected them. Studies by researchers at Dartmouth College suggest that mammography also leads to overdiagnosis and overtreatment. About 25 percent of breast cancers discovered, and treated, would not have caused any symptoms.”
If you’re interested in reading about other new medical tests, check out the new urine test that could catch pancreatic cancer super early, as well as a new test that can ‘detect virtually any virus.’
 The Verge
 NBC News