optimal timing of computed tomography for assessing lymph nodes after neoadjuvant chemoradiotherapy for rectal cancer

background: this study assessed the optimal timing of computed tomography for detection of metastatic disease in locoregional lymph nodes in patients with rectal cancer who have undergone chemoradiotherapy. materials and methods: this observational retrospective study was performed in a single institution. all patients with locally advanced rectal cancer treated with chemoradiotherapy, followed by a total mesorectum excision from january 1, 2003 to december 31, 2012, were included. lymph node metastases evident on preoperative computed tomography were compared with postoperative pathologic lymph node status. results: the study population consisted of 108 patients: group a (nodal negative on preoperative computed tomography, n = 52) and group b (nodal positive on preoperative computed tomography, n = 56). analysis of the computed tomography scans in group a revealed a high ability (98.07%) to predict negative lymph nodes, compared to 58.92% for predicting positive lymph nodes in group b. conclusion: the results of this study suggest that the optimal timing of computed tomography for assessing lymph nodes after neoadjuvant chemoradiotherapy for rectal cancer is after 6 weeks; this timing might be key for prediction of complete clinical responses.