AROMA 1 Inclusion Criteria:

1. Aged 18-90years
2. Oesophageal/gastric cancer cohort: participants with biopsy proven adenocarcinoma who are treatment naïve
3. Control cohort: participants with normal or benign upper gastrointestinal disease determined on: • Endoscopy within 1 year • Planned endoscopy

AROMA 1 Exclusion criteria:

Patients with the following characteristics will not be eligible for inclusion in this study:

1. Oesophageal squamous cell carcinoma
2. Previous oesophageal and gastric resection
3. Received neoadjuvant chemotherapy for oesophageal or gastric cancer
4. History of another cancer within three years
5. Any form of oesophageal dysplasia (control cohort only)
6. Previously diagnosed with Barrett's oesophagus (control cohort only)
7. Active infection, on immunosuppressive medications or antibiotic therapy within the last 8 weeks
8. Participants with co-morbidities preventing breath collection
9. Allergies to any of the constituents of the nutrient drink including glucose, glycerol, iron sulphate, Maltodextrin (Corn, Potato), Xanthan Gum, Potassium Chloride, tyrosine, phenylalanine, and glutamic acid
10. Unable or unwilling to provide informed written consent
11. Pregnant participants

BIORESOURCE inclusion criteria:

1. Aged 18- 90years
2. Oesophageal/gastric cancer cohort: participants with biopsy proven adenocarcinoma who are treatment naïve
3. Oesophageal/gastric control cohort: participants with normal or benign upper gastrointestinal disease determined on: • Planned endoscopy

BIORESOURCE exclusion criteria:

1. Oesophageal squamous cell carcinoma
2. Previous oesophageal and gastric resection
3. Received neoadjuvant chemotherapy for oesophageal or gastric cancer
4. History of another cancer within five years
5. Any form of oesophageal dysplasia (oesophageal/gastric control cohorts only)
6. Previously diagnosed with Barrett's oesophagus (oesophageal/gastric control cohorts only)
7. Active infection, on immunosuppressive medications or antibiotic therapy within the last 8 weeks
8. Participants with co-morbidities preventing breath collection
9. Unable or unwilling to provide informed written consent
10. Pregnant participants