Early Detection of Gastric Cancer Using Plasma Cell-free DNA Fragmentomics

Inclusion Criteria:

* Age minimum 18 years
* Participants must have histologically and/or cytologically confirmed stage I/II gastric cancer
* Full access to the patients' clinical and pathological records
* Ability to understand and the willingness to sign a written informed consent document
* Non-cancer controls are sex- and age-matched individuals without presence of any tumors or nodules or any other severe chronic diseases through systematic screening

Exclusion Criteria:

* Participants must not be pregnant or breastfeeding
* Participants must not have prior cancer histories or a second non-gastric malignancy
* Participants must not have had any form of cancer treatment before enrollment or plasma collection, including surgery, chemotherapy, radiotherapy, targeted therapy and immunotherapy
* Participants must not present medical conditions of fever or have acute or immunological diseases that required treatment 14 days before plasma collection
* Participants who underwent organ transplant or allogenic bone marrow or hematopoietic stem cell transplantation
* Participants with clinically important abnormalities or conditions unsuitable for blood collection
* Any uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, myocardial infarction, major seizure disorder, unstable spinal cord compression, superior vena cava syndrome, or psychiatric illness/social situations that would limit compliance with study requirements or influence patient signing the written informed consent