Early Postoperative Serum Carcinoembryonic Antigen Is a Stronger Independent Prognostic Factor for Stage II Colorectal Cancer Patients Than T4 Stage and Preoperative CEA oleh Du Fenqi, Liu Yupeng, Zhang Qiuju, Yuan Chao, Song Wenjie, Xia Tianyi, Guo Junnan, Xue Weinan, Jiang Xiufeng, Bai Junge, Jia Chenyang, Xi Hua, Li Yien, Bai Xuefeng, Liu Yanlong