Can you smell cancer on someone's breath? Humans might not be able to, but previous research suggests dogs can-and if dogs can, it likely means you can train a machine to do so as well.
It's why Marcis Leja, MD, PhD, Director of the Institute of Clinical and Preventive Medicine at University of Latvia and Head of the Department of Research at Riga East University Hospital, and his colleagues (and several other groups) are currently working on developing a portable point-of-care sensor breath analyzer that can detect presence of various diseases-including some types of cancer-based solely on a sample of an individual's breath.
Previous research suggests that breath samples of people with cancer have volatile organic compounds (VOCs) at detectable levels (Eur Respir Rev 2019; doi: 10.1183/16000617.0002-2019; Clin Ter 2016; doi: 10.7417/CT.2016.1943). There are two different methods of testing breath for VOCs-you either catch the chemicals themselves and measure them or you use sensors that react to the presence of the chemicals, Leja explained.
The portable cancer breath test being developed by Leja's team uses the second mechanism. The result of the test is a map of the chemicals found in an individual's breath. "Just like a fingerprint is unique for each person, so is a 'breath' print," he noted. These breath prints can also reveal presence of cancer or not.
Previous research showed that the technique can be used in a laboratory setting and accurately detect which individuals in a group have gastric cancers and which don't based on breath samples alone (Br J Surg 2019;106:1122-1125). But that research was done in a lab, where the breath samples need to be transported to the lab's location for analysis. Now the team has published a new proof-of-concept study that shows a portable version of the test can accurately detect gastric cancer, too (Cancer 2021; https://doi.org/10.1002/cncr.33437).
The team's portable test will require more validation trials before it can be used clinically, Leja added. "Although huge progress has been achieved during the last decade, we still expect it to take few years before the tests will be used in clinics."
But this new research is a step in the right direction in terms of putting the test to clinical use. In an interview with Oncology Times, Leja discussed the test and its potential to change cancer screening.
1 Why is developing this type of breath test for cancer so important?
"Rates of gastric cancer are declining overall. But if you look closer, we see that incidence is higher in older populations-and the populations of older adults are increasing globally-so we do expect gastric cancer rates to increase in the coming years.
"Improving screening strategies to catch these increasing cases of gastric cancer sooner will be important because it's one of the deadliest types of cancer. Currently, the only effective screening strategy is endoscopy, but it's still an invasive procedure that's not cost-effective to do frequently (given that overall incidence of gastric cancers is still somewhat moderate at a population level).
"This new study is important because we show that this point-of-care testing that can be done anywhere can accurately detect gastric cancers. But further method validation studies, instrument-to-instrument variability studies and, finally, large-scale implementation studies are still required [before these types of tests can be used clinically]."
2 Could the test be used to detect other types of cancer in addition to gastric cancer?
"Yes, research in dogs showed that dogs can successfully 'sniff' out several types of cancer, including urogenital cancers and breast cancer, among others. So, the assumption is if a dog can detect those cancers, you can train a machine to do it, too.
"We've now shown that we can do this with gastric cancer. But more research will be needed to identify the compounds in breath associated with those other cancers and then develop machine methods of detecting them. And other research has shown that you could use this method to detect other diseases in addition to cancer, too.
"But we still don't completely understand what makes the breath of someone with cancer different from the breath of someone without cancer. The project our group is currently working on is addressing this question of better understanding the mechanism of what creates these compounds in the breath of people with cancer that aren't in the breath of people without cancer."
3 What's the bottom-line message cancer care providers should know about this work now?
"Oncologists should know that this screening methodology is coming. These tools are in development and there's a growing body of evidence that they can work. And clinicians shouldn't be surprised when these tools are ready to be used in clinical settings."