OBJECTIVETo analyze the association between the response of primary tumor to neoadjuvant chemoradiotherapy (CRT) and lymph node status in mid and low rectal cancer.

METHODSSeventy-one patients with locally advanced mid and low rectal cancer underwent preoperative CRT followed by surgery. Surgical specimens were examined by surgeons and pathologists to obtain more lymph nodes and the histological sections were examined. Tumor responses to preoperative CRT were assessed in terms of tumor downstaging and tumor regression. Statistical analyses were performed to investigate the relationship between tumor regression and lymph node status.

RESULTSAll the patients completed the neoadjuvant CRT. Twelve patients achieved pathological complete response, of whom one was not operated and on surveillance. Pathological examination of the remaining 70 patients showed that the tumor was downstaged to T 0-2 group in 39 patients, among whom 5 patients (12.8%) had positive lymph nodes. Tumor was not downstaged in 31 patients, of whom 10 patients (32.3%) had positive nodes. The difference between the two groups was statistically significant (P=0.029).

CONCLUSIONTumor regression is consistent with the reduction of lymph node metastasis after preoperative CRT.