Zhenhui Li,1,* Shaoyou Li,2,* Yun Liang,3,* Hongjiang Pu,4 Changling Tu,5 Zhenyu Wu,6 Dingyun You7,8 1Department of Radiology, The Third Affiliated Hospital of Kunming Medical University, Yunnan Cancer Hospital, Yunnan Cancer Center, Kunming 650118, People’s Republic of China; 2Department of Medical Oncology, The First Affiliated Hospital of Kunming Medical University, Kunming 650032, People’s Republic of China; 3Department of Hepatobiliary Surgery, The First Affiliated Hospital of Kunming Medical University, Kunming 650032, People’s Republic of China; 4Department of Colorectal Surgery, The Third Affiliated Hospital of Kunming Medical University, Yunnan Cancer Hospital, Yunnan Cancer Center, Kunming 650118, People’s Republic of China; 5Department of Cadres Medical Oncology, The Third Affiliated Hospital of Kunming Medical University, Yunnan Cancer Hospital, Yunnan Cancer Center, Kunming 650118, People’s Republic of China; 6Department of Biostatistics, School of Public Health, Key Laboratory of Public Health Safety and Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, Shanghai 200032, People’s Republic of China; 7The Department of Epidemiology & Biostatistics, School of Public Health, Kunming Medical University, Kunming, Yunnan 650500, People’s Republic of China; 8Yunnan Key Laboratory of Laboratory Medicine, Kunming Medical University, Kunming, Yunnan 650500, People’s Republic of China*These authors contributed equally to this workCorrespondence: Dingyun YouYunnan Key Laboratory of Laboratory Medicine, Kunming Medical University, No. 1168 Chunrongxi Road, Chenggong District, Kunming, Yunnan 650500, People’s Republic of ChinaTel/ Fax +86 871-5922935Email youdingyun@qq.comZhenyu WuDepartment of Biostatistics, School of Public Health, Key Laboratory of Public Health Safety and Collaborative Innovation Center of Social Risks Governance in Health, Fudan University, 130 Dongan Road, Shanghai, People’s Republic of ChinaTel/ Fax +86 21â33563913Email nc.ude.naduf@wyzObjective: Association of postoperative peripheral CD4+ T cells percentage and recurrence in colorectal cancer (CRC) remains to be explored. Therefore, we aimed to investigate the association between the postoperative peripheral CD4+ T cells percentage and recurrence in CRC patients.Patients and Methods: Consecutive stage I–III CRC patients without neoadjuvant treatment undergoing curative resection from January 2010 to July 2016 were identified in two Chinese centers. The association between the postoperative CD4+ T cells percentage, measured within 12 weeks after surgery, and recurrence-free survival (RFS) was analyzed.Results: A total of 1028 patients were identified (training set: 913 patients, validation set: 115 patients). In the training set, the 5-year RFS rate of the 441 patients with abnormal postoperative CD4+ T cells percentage was significantly lower than that of those with normal percentage (70.3% [95% CI 65.7– 75.2%] vs 77.6% [95% CI 73.7– 81.7%] and unadjusted hazard ratio [HR] 1.36 [95% CI 1.04– 1.78], P= 0.02). The result was confirmed in the validation set. Multivariable Cox regression analysis demonstrated that the association of postoperative CD4+ T cells percentage with 5-year RFS was independent both in the training and validation sets. In propensity score matching analysis, patients with normal postoperative CD4+ T cells percentage were found to have a favourable response to adjuvant chemotherapy (HR 0.29 [95% CI 0.12– 0.72], P=0.008).Conclusion: Postoperative peripheral CD4+ T cells percentage is a predictive biomarker for RFS in patients with CRC, which can identify those who will benefit from adjuvant chemotherapy.Keywords: recurrence, peripheral CD4+ T cells, colorectal cancer, adjuvant chemotherapy, propensity score matching analysis