This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Small & Large Intestine, Subject name: Surgery
[{'content': 'Colonic metastases are related with: \nSelect and explain. \nA. Preoperative CEA level, B. Depth of invasion, C. Size of tumor, D. Circumferential involvement', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Depth of invasionRef: Schwartz 9th edition, Page 1046; Shackelford 7th edition, Page 2133* Colonic metastasis to liver is related to -- depth of invasion (T stage)* CRC prognosis depends on the stage of the disease (Especially in stage on the lymph node status)* Tumor size and duration has no effect on prognosis.', 'role': 'assistant'}]