The purpose of this study is to investigate whether exhaled breath can be used to detect and monitor esophageal cancer.

Esophageal cancer ("EG cancer") affects over half a millions people worldwide every year. Early esophageal cancer typically has non-specific symptoms that are often mistaken for benign (non-cancer) conditions. As a result, patients are often referred for further investigations only when they have more prominent symptoms that are typically associated with advanced incurable disease. As a consequence, 7 out of 10 new cases of EG cancer diagnosed are considered to be at an advanced stage, with less than 1 in 3 patients eligible for potentially curative therapy. Better ways of diagnosing esophageal cancer earlier are therefore needed. An ideal test for esophageal cancer would be non-invasive, simple to administer in the community, and cost effective.

The investigators' approach to this clinical challenge is to establish a non-invasive test for the detection of esophageal cancer that is based upon the unique signature of small molecules within exhaled breath. In this study that is being conducted in collaboration with researchers in the United Kingdom (UK), the investigators would like to measure the levels of these small molecules within the breath of patients with esophageal cancer at different times during their treatment: (i) at diagnosis; (ii) after chemoradiotherapy, and; (iii) after surgery. By studying how the small molecules contained within the breath change as a result of esophageal cancer and its treatment, the investigators hope to learn new information that can help develop a new test for this disease.

The investigators will also measure the small molecules within saliva and urine samples collected at the same time as breath in order to study if there are any important differences between these three samples. The investigators will also attempt to measure different bacteria

Inclusion Criteria:

• Aged 18-90 years
• Newly-diagnosed, treatment naïve patients with esophageal and/or gastroesophageal junctional cancer
• Planning to undergo curative treatment, including neoadjuvant chemoradiotherapy and surgical resection

Exclusion Criteria:

• Pregnant females
• Without malignant esophageal disease
• Malignancy at a secondary site other than the esophagus
• Undergoing palliative treatment for esophageal cancer
• Not receiving neoadjuvant chemoradiotherapy and surgical resection for esophageal cancer
• Inability or unwillingness to provide written informed consent

IPD is not required for analysis. Study ID used to represent study participants.