There has been a significant amount of research over recent years in the field of diagnosing illness through breath tests. A quick exhale into a device could prove a cheap, effective revolution in early diagnosis, so it's no surprise we've seen everything from an artificially intelligent nanoarray that recognizes the chemical signatures of 17 different diseases in a person's breath to a hand-held breathalyzer that can indicate if a patient has diabetes.

For several years, Professor George Hanna from Imperial College London has been directing work toward the development of a test that can detect cancers of the esophagus and stomach by measuring the levels of five chemicals in a patient's breath. These chemicals are butyric, pentanoic and hexanoic acids, butanal, and decanal, which previous research has identified as pointers to the presence of stomach or esophageal cancer.

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In 2015, Professor Hanna announced the results of the first clinical study analyzing the breath samples of 210 patients. The patents exhaled into a breathalyzer-like device, which used a selected ion flow tube mass spectrometer to detect the presence of any of the five aforementioned chemicals in the breath sample. The 2015 study achieved a 90 percent accuracy rate in correctly identifying the two cancers, and a recently completed, broader study has also proven successful.

The new study collected samples from 335 people across four London hospitals. Around half of the group had been diagnosed with stomach or esophageal cancer and the other half had shown no evidence of cancer after having an endoscopy. After analyzing all the samples, the new breath test achieved an 85 percent accuracy rate, correctly identifying those both with and without cancer.

Around 1.4 million people worldwide are diagnosed with stomach or esophageal cancer every year. Both cancers are known to be especially terminal, with a combined five-year survival rate of only 15 percent, as symptoms are often frustratingly abstract resulting in frequent late-stage diagnosis.

"At present the only way to diagnose esophageal cancer or stomach cancer is with endoscopy," points out Dr Sheraz Markar, an NIHR Clinical Trials Fellow at Imperial. "This method is expensive, invasive and has some risk of complications. A breath test could be used as a non-invasive, first-line test to reduce the number of unnecessary endoscopies. In the longer term this could also mean earlier diagnosis and treatment, and better survival."

While the results of these studies point to exciting new diagnostic possibilities, the researchers still have work to do. They are currently expanding to an even bigger trial over the next three years, using the test on patients who are undertaking endoscopies for undiagnosed gastrointestinal symptoms. Dr Markar hopes this will asses the ability of the test to pick up cases in a larger sample of patients containing a smaller percentage of cancers.

The scientists are also attempting to broaden the scope of their studies to develop breath tests for other cancers including colorectal and pancreatic.

The team presented their study this week in Amsterdam at the European Cancer Congress 2017 and it can be viewed here.

Source: European CanCer Organisation (ECCO) via EurekAlert