Pathologists may do fewer lung biopsies should non-invasive breath testing technology make it into clinical practice
Here’s a medical laboratory test for diagnosing cancer that has the potential to score two runs with one swing of the bat. First, researchers have completed the first clinical trial of a non-invasive cancer test that utilizes a breath specimen.
Second, the subject of this clinical trial was lung cancer—a type of cancer that would benefit from a pathology test that can detect the disease much earlier. This would increase the survival rates for lung cancer, which currently has a five-year mortality rate of 90%.
As many pathologists and clinical laboratory managers know, it is possible to use breath specimens to diagnose a variety of diseases and health conditions. For almost 20 years, breath samples have been used to test for Helicobacter pylori, the bacteria which causes ulcers in the stomach.
Test Moves Closer to Accurate, Non-invasiveness Lung Cancer Diagnosis
In testing for lung cancer, one problem for researchers has been to develop a test that is simple, reliable and sufficiently portable, stated a story in Technology Review (TR). A recent clinical trial by Mountain View, California-based startup Metabolomx showed that its new breath test can analyze a patient’s breath at bedside and detect lung cancer with 83% accuracy.
“The idea of applying a breath test at the patient’s bedside and getting a result without even requiring a stick of a needle would be the ultimate in noninvasiveness,” declared Peter Mazzone, M.D., M.P.H., Director of the Lung Cancer Program at Cleveland Clinic’s Respiratory Institute, in a Business Week (BW) story on the new test. Mazzone led the recent clinical trial.
Mazzone studied 229 people and, by using an early version of the Metabolomx machine, determined that it could detect lung cancer more than 80% of the time. The test distinguished between different forms of lung cancer with about 85% accuracy. This helped doctors determine the cancer’s aggressiveness.
The Metabolomx machine detects chemical results of tumor metabolism which are dissolved in the blood and can be present in the breath. The machine itself resembles a desktop PC with a hose attached. The unit sits on a cart that can be wheeled to the bedside, where the patient breathes in and out of the hose for about four to five minutes.
Pumps draw the breath through a series of filters to dry it out and remove bacteria, TR reported. It then draws the breath over an array of sensors, consisting of colored reactants. Each reactant is sensitive to a different group of volatile organic compounds (VOC). The different VOCs in the breath will change color to varying degrees. The system takes before and after photos of the array of colored reactants. It then subtracts one image from the other and produces a colored pattern for the breath sample.
Breath Testing Could Reduce Use of CTs and Biopsies
The new test offers advantages over existing methods and could potentially reduce the number of biopsies and computed tomography (CT) scans. For example, current testing with gas chromatography-mass spectrometry (GC/MS) cannot be done bedside and requires special operator expertise.
Also, the accuracy of the new machine is comparable to the accuracy of low-dose CT imaging of the lungs. CT imaging will often display spots on lung scans, BW reported. However, without a biopsy, it can be difficult to determine whether the spots indicate cancer or sub-type when cancer is present.
“We think it is a very good pre-screening tool to identify who gets a CT scan because they do have a certain amount of radiation,” Rhodes observed in the NBC piece. Mazzone added that a noninvasive metabolic breath test could help doctors make better decisions when a CT scan looks suspicious. James R. Jett, M.D., Professor of Medicine at National Jewish Health Hospital in Denver, observed in the BW story that, although further development is needed, it is now conceivable that such new technology could eventually replace a test like a biopsy.
Researchers associated with this project now want to conduct new clinical trials using an updated version of the Metabolomx machine that is 100 to 1,000 times more sensitive. They will try to determine whether it can achieve a 93% accuracy rate. This is the figure that doctors say would make the device viable for widespread use, BW reported.
Metabolomx’ Rhodes expects a $75 price point for the breath test. He also sees expanded potential for breath testing. “One day this could possibly be applied during chemotherapy to see if the tumor changes and gives off different signals, so that you know if the medicine is working,” he commented in Business Week. In fact, he noted, it is conceivable that the new test could be used to screen for any disease that has a metabolic breath signature.
Pathologists and clinical laboratory managers will note that the continued advance in breath testing means that the introduction into the marketplace of useful clinical laboratory tests based on breath analysis is getting nearer. In addition, pathologists and pathology groups will want to consider the longer-term impact of such new technology on biopsy testing.
—Pamela Scherer McLeod