A composite endpoint approach can help assess outcomes in simultaneous resections for colon cancer with synchronous liver metastases, improving clinical trial efficiency.

• In a study of 1,591 patients, 24.3% had a positive composite postoperative endpoint (CELCSS), indicating potential complications.
• CELCSS includes key issues like colon anastomotic leak (15.4%) and postoperative bleeding (6.5%), predicting prolonged hospital stays and 30-day mortality with good accuracy.

Using this endpoint can reduce sample size requirements by 41.4% to 88.5%, enhancing trial feasibility and focus in surgical practices.