Circulating tumor cells: A promising marker of predicting tumor response in rectal cancer patients receiving neoadjuvant chemo-radiation therapy

// Wenjie Sun 1, 2 , Guichao Li 1, 2 , Juefeng Wan 1, 2 , Ji Zhu 1, 2 , Weiqi Shen 2, 3 , Zhen Zhang 1, 2 1 Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China 2 Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China 3 Department of Pathology, Fudan University Shanghai Cancer Center, Shanghai 200032, China Correspondence to: Zhen Zhang, email: zhenzhang6@hotmail.com Keywords: circulating tumor cells, rectal cancer, neoadjuvant chemo-radiation therapy, prediction Received: February 4, 2016     Accepted: July 14, 2016     Published: July 28, 2016 ABSTRACT Purpose : The aim of this study was to investigate the role of circulating tumor cells (CTCs) in assessing and predicting tumor response to neoadjuvant chemoradiotherapy (CRT) for patients with locally advanced rectal cancer (LARC). Methods : A total of 115 patients with T3-4 and/or N+ rectal cancer were enrolled. All patients received neoadjuvant CRT followed by radical surgery after 6-8 weeks. The pathological results after surgery were evaluated according to tumor regression grade (TRG) classification. Results : Based on TRG score, patients were classified as responders (TRG3-4) and non-responders (TRG0-2). The baseline CTC counts of responders were significantly higher than those of non-responders (44.50±11.94 vs. 37.67±15.45, P=0.012). By contrast, the post-CRT CTC counts of responders were significantly lower than those of non-responders (3.61±2.90 vs. 12.08±7.40, P<0.001). According to ROC analysis, Δ%CTC (percentage difference in CTC counts between baseline and post-CRT) was identified as the stronger predictor to discriminate responders from non-responders (AUC: 0.860). The results of multivariate analysis also indicated that post-CRT CTC counts and Δ%CTC were significantly and independently associated with tumor response to CRT. Conclusions : The detection of CTCs is a powerful and promising tool for evaluating and predicting responses to neoadjuvant CRT in LARC patients.