Someday soon a breath test could do more than just tell if you’ve been drinking. Metabolomx, a startup in Mountain View, California, recently completed a clinical trial that shows that its breath test can spot lung cancer with 83 percent accuracy and can also distinguish between several different types of the disease, something that usually requires a biopsy. The accuracy of the test matches what’s possible with low-dose computerized tomography imaging of the lungs.
Existing tests for lung cancer—the leading cause of cancer death worldwide—cause too many false positives, which means patients face unnecessary biopsies or exposure to radiation from imaging, and none are currently approved by Medicare. A breath test promises much simpler, safer screening.
Chemical results of a tumor’s metabolism are dissolved in the blood, and can end up in the breath. Trained dogs can identify breath samples from patients with lung cancer with 98 percent accuracy. Researchers have been working on a noninvasive cancer breath test for years, but have struggled to make one that is simple, reliable, and portable enough. A method called gas chromotography-mass spectrometry can detect metabolites in the breath, but it can’t be done at the bedside, and requires some expertise to operate.
Paul Rhodes, the founder and CEO of Metabolomx, says the company is now running additional lung and colon cancer clinical trials of equipment that is 1,000 times more sensitive to biomarkers carried on the breath than the one used in its recently completed clinical trial. That could help them get to 90 percent accuracy, which Rhodes believes will be necessary to get the test to market.
Peter Mazzone, a pulmonologist at the Cleveland Clinic, who is running clinical trials of the new system, says a noninvasive metabolic breath test could help doctors make a better decision when a CT scan looks suspicious. Today, when doctors find a nodule in a patient’s scan, they have to follow up periodically to see if the nodule gets bigger, and then do a biopsy. And eventually Mazzone hopes a metabolic breath test could help predict the behavior of a particular cancer and what drugs it will respond to: “How aggressive is it? Do we need to simply remove it, or remove it and give chemotherapy?”
In the current version of the system, a patient must breathe through a tube for about five minutes. Pumps draw the breath through a series of filters to dry it out and remove bacteria, then over an array of sensors. Metabolomx has shown that the system can distinguish breath samples from patients with different subtypes of lung cancer.
The sensor array consists of colored reactants that are each sensitive to a different group of volatile compounds. Depending on what’s in the sample, different spots in the array—24 in the version used for the initial clinical trial, 130 in the current one—will change color to varying degrees. The system takes a photo of the array of colored reactants before and after they’re exposed to the breath sample, subtracts one image from the other, and generates a colored pattern for that sample.
Rhodes expects a test to cost $75. Also, because it’s not specific to a particular group of chemicals, the Metabolomx sensor could, in theory at least, be used to screen for any disease that has a metabolic breath signature—the company is currently exploring tests for other diseases, including tuberculosis. “A breath signature could give a snapshot of overall health,” Rhodes says.
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