The standard treatment for advanced gastric cancer without metastases is gastrectomy, where the whole stomach or a large proportion is removed surgically together with regional lymph nodes. Some patients cannot tolerate this invasive procedure because of old age or comorbidities. A tumor left in place can cause local symptoms such as bleeding or outlet obstruction. In this study, the investigators want to test the safety and feasibility of Laparoscopic and Endoscopic Collaborative Surgery (LECS) as a less invasive treatment option to locally remove gastric tumors without requiring extensive surgery in these frail patients. LECS is a minimally invasive surgical technique where the tumor margin is first marked from the inside with a gastroscope, followed by surgical removal of the lesion under endoscopic guidance.