Surgery is the mainstay of treatment for patients with early-disease esophageal and gastric cancer. Open surgery for oesophageal cancer commonly involves large incisions in the chest, which is associated with a high rate of respiratory complications in the postoperative period. Patients with oesophageal or gastric cancer furthermore commonly present with significant weight loss, affecting both muscle mass and muscle strength. This could further decrease the physical fitness and increase the risk for experiencing complications after treatment. Patients also report a decreased physical functioning in quality of life at least 3 years after surgery, suggesting this is a persistent deficit. Currently, no long-term data is available assessing physical activity levels in oesophageal or gastric cancer survivors. Thus, quantifying physical activity levels in these patients may identify the period in which patients' activity levels are most likely to deteriorate. Activity levels will be assessed from Google Location History from the patient's phone, providing summary of physical activity over time. This information could be used in the future to provide adequate physical therapy intervention which might improve recovery in several aspects, such as physical fitness but also respiratory function and quality of life.

Surgery is the mainstay of treatment for patients diagnosed with early-disease esophageal and gastric cancer. Open surgery for oesophageal cancer commonly involves large incisions in the chest, which is associated with a high rate of respiratory complications in the postoperative period. Several studies have shown that low physical activity levels are associated with increased risk for respiratory complication. Furthermore, patients with oesophageal or gastric cancer often present with significant weight loss, affecting both muscle mass and muscle strength. This could further decrease the physical fitness and increase the risk for experiencing complications after treatment. Moreover, open oesophagectomy involves thoracotomy, thus impairing respiratory mechanics with further deterioration in physical fitness. Patients also report a decreased physical functioning in quality of life at least 3 years after surgery, suggesting this is a persistent deficit. Currently, no long-term data is available assessing physical activity levels in oesophageal or gastric cancer survivors. Enhanced recovery programmes are evidence-based protocols aiming at early recovery after surgery with early mobilisation and physiotherapy, and have been shown to reduce respiratory complication rates. Thus, quantifying physical activity levels in these patients may identify the period in which patients' activity levels are most likely to deteriorate and whether these changes in physical activity are associated with changes in quality of life. Activity levels will be assessed from Google Location History from the patient's phone, providing summary of patterns of physical activity over time. This information could be used in the future to provide adequate physical therapy intervention which might improve recovery in several aspects, such as physical fitness but also respiratory function and quality of life.

Inclusion Criteria post-oesophagectomy or -gastrectomy group:

• is 18 years or older, and below 90 years of age, AND
• be able to walk, run or cycle a short distance, AND
• has been diagnosed with or already treated for oesophageal or gastric cancer
• if already receiving treatment, any type of treatment is included, either surgical resection for early-stage disease or definitive chemotherapy for advanced disease, AND
• use and Android phone

Inclusion Criteria healthy controls:

• is 18 years or older, and below 90 years of age, AND
• no previous history of upper gastrointestinal cancer, AND
• not diagnosed with or undergoing treatment for active cancer since active cancer or cancer-related treatment might influence physical activity levels and quality of life, AND
• be able to walk, run or cycle a short distance, AND
• use an Android phone

Exclusion Criteria:

• lacks capacity or is unable to provide informed consent, OR
• below 18 years of age or over 90 years of age, OR
• cannot walk, run or cycle a short distance, OR
• is diagnosed with or undergoing treatment for active cancer other than oesophageal or gastric cancer, OR
• is pregnant, OR
• is not using an Android phone, as Google Location History data is only accessible from an Android device

There will be three cohorts, consisting of post-oesophagectomy patients, post-gastrectomy patients and a third group consisting of healthy controls.

The participants will be eligible if aged 18 years or older, up to 90 years of age.

Participants will be eligible if they can provide informed consent and can walk, run or cycle a short distance, and if they are using an Android phone.

All identifiable data will be anonymised. No data will be shared to other researchers outside the research team for the study.