A test 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 presented by Markar et al at the 2017 European Cancer Congress (Abstract 6LBA).1
https://www.univadis.fr/viewarticle/ecco-2017-breath-test-might-help-detect-stomach-and-esophageal-cancers-488724
ECCO 2017: Breath Test Might Help Detect Stomach and Esophageal Cancers