Inclusion Criteria:  AJCC stage I-III who has undergone radical gastric cancer surgery (chemotherapy, radiation therapy is irrelevant) Patients aged 19 to 75 years old Those who can use prognosis management applications and can perform regular follow-up inspections outpatients Patients carrying Android or iOS smartphones Patients who voluntarily decide to participate and give written consent after hearing detailed explanations about this study  Exclusion Criteria:  Those who have difficulty using gastric cancer applications (exercise performance, diet management, etc.) due to severe underlying diseases, neuromusculoskeletal diseases, cognitive, and visual impairments