A test has been developed that measures the levels of five chemicals in the breath has shown promising results for the detection of cancers of the esophagus and stomach in a large patient trial.
https://www.labmedica.com/pathology/articles/294768205/breath-test-helps-detect-stomach-and-esophageal-cancers.html
Breath Test Helps Detect Stomach and Esophageal Cancers