A study presented at a scientific meeting suggests we are getting closer to having a reliable, non-invasive breath test for lung cancer. Led by the University of Colorado Cancer Center in Denver, the study shows how a device that uses a gold nanoparticle sensor can not only tell whether exhaled breath has come from a patient with COPD or lung cancer, but it can also sense whether the cancer is in early or advanced stages.
The study is the work of Fred R. Hirsch, professor of medical oncology at the University of Colorado School of Medicine, and colleagues, and was presented at the 50th Annual Meeting of the American Society for Clinical Oncology (ASCO) in Chicago, IL.
Prof. Hirsch says a breath test for lung cancer could "totally revolutionize lung cancer screening and diagnosis. The perspective here is the development of a non-traumatic, easy, cheap approach to early detection and differentiation of lung cancer."
This is not the first time that the promise of a breath test for lung cancer, and other cancers, has hit the headlines. For example, as far back as 2007, Medical News Today reported a prototype breath test for lung cancer that used a colorimetric sensor array to analyze the chemical fingerprint of exhaled breath.
Considerable challenge to overcome is generation of false positives
However, there is a big difference between showing that the method is feasible, and whether it will work in clinical settings.
The metabolism of people with lung cancer is different to that of healthy people, and this is reflected in the chemical signature of their breath. Researchers say we are closer to a breath test for lung cancer.
For example, in the prototype tested in 2007, there was a high rate of false positives - the test also picked out people without lung cancer. It is also important that the test distinguishes between cancer and other conditions, which is what this latest study undertakes to do.
Prof. Hirsch says there is a need for improved screening and diagnostic tools for lung cancer, following the release of new lung cancer screening guidelines from the US Preventive Task Force. They showed that screening via low-dose computed tomography can reduce disease mortality by 20%.
He explains that the metabolism of people with lung cancer is different to that of healthy people and this is reflected in the chemical signature of their breath. Thus, it should be possible to differentiate among people with lung cancer, healthy subjects and also those with other lung conditions like chronic obstructive pulmonary disease (COPD).
However, he points out that the challenge to tool developers is that the more sensitive you try to make the screening tool, the higher the chance that you will pick up false positives. In the case of lung cancer, this is detecting non-cancerous lung nodules, as he explains:
"You detect many, many nodules in those screenings and unfortunately, around 90% of them are benign. So you need to find out how to better distinguish malignant from benign modules. The goal of this tool is to use breath biomarkers to distinguish malignant from benign screen-detected nodules."
Nanosensor distinguished among COPD, advanced and early lung cancer
The device that they tested requires subjects to blow up a balloon that is then connected to a very sensitive gold nanoparticle sensor that traps and analyzes the volatile organic compounds (VOCs) in the exhaled breath sample. The team that developed the device includes researchers from the University of Colorado Cancer Center working with the Nobel-Prize-winning Technion University in Haifa, Israel.
The study enrolled 358 patients in Israel, Denver and Florida. Of them, 213 were lung cancer patients, including 62 with early stage and 143 with advanced stage disease. The other 145 patients did not have cancer.
A preliminary analysis of 80 lung cancer patients (64 with advanced stage) and 31 patients with COPD, showed that the nanosensor array distinguished significantly between COPD and lung cancer (accuracy of 85%), COPD and advanced lung cancer (accuracy of 82%), and early and advanced lung cancer (accuracy of 79%).
Prof. Hirsch sees the device going further than initial screening or diagnosis. For instance, it could measure changes in patients' breath signatures over time to see how well they respond to treatment. They are already working on such an application at the Cancer Center.
Another possibility is to make a simple, cheap and rapid test that helps doctors identify a patient's lung cancer subtype to ensure earlier and faster selection of appropriate targeted therapy.
He pictures a future possible scenario: "imagine standing in the grocery store and having high risk people blow into a balloon or a USB device, and the profile of the organic compounds in their breath would tell you if they are at risk for developing or having lung cancer, which then could lead to further, focused tests."
Written by Catharine Paddock PhD