[Study on the relationship between tumor regression grade and lymph node regression grade]

To investigate the relationship between tumor regression grade (TRG) and lymph node regression grade (LRG) after neoadjuvant chemoradiotherapy (CRT) for rectal cancer and its clinical implication.

Clinicopathological data of 176 rectal cancer patients undergoing radical excision after neoadjuvant CRT from January 2005 to December 2013 in our department were retrospectively analyzed.

(1) Radiology indicated locally advanced low rectal cancer and patients had strong desire to preserve the sphincter before neoadjuvant CRT; (2) there was no definite metastatic lesion before neoadjuvant CRT; (3) patients received whole course of neoadjuvant CRT (regular radiotherapy plus synchronous fluorouracil-like drugs chemotherapy); (4) patients underwent radical operation after neoadjuvant CRT. Patients with short-course CRT and emergency surgery were excluded. TRG and LRG of postoperative specimens (including tumor and lymph nodes) were carried out based on the percentage of the fibrosis and the cancer residue. No cancer residue was defined as TRG1 and LRG1; rare cancer cell residue as TRG2 and LRG2; fibrosis growth over residual cancer as TRG3 and LRG3; residual cancer growth over fibrosis as TRG4 and LRG4; absence of regressive changes as TRG5 and LRG5; and normal lymph nodes as LRG0. Spearman correlation test was used to assess the correlation between TRG and LRG.

Of 176 patients, 111 were men and 65 were women. The mean age was (53.9±13.0) years. The number of patients with stage I(, II(, and III( before operation was 10, 49 and 62 while other 55 patients were unknown. Transabdominal low anterior resection (LAR) was performed in 118 cases and abdominal-perineal resection(APR) in 47 cases following the principle of total mesorectal excision (TME). Postoperative pathology of specimens revealed that the number of patients from TRG1 to TRG5 was 19 (10.8%), 25 (14.2%), 66 (37.5%), 47 (26.7%), 19 (10.8%), and from LRG0 to LRG5 was 35 (19.9%), 68 (38.6%), 10 (5.7%), 14 (8.0%), 15(8.5%), 34 (19.3%), respectively. TRG was correlated to LRG (P=0.005) while the Spearman correlation coefficient was only 0.24. The analysis of subgroup without LRG1 also showed that TRG was correlated to LRG(P=0.0005) and the Spearman correlation coefficient was 0.40.

TRG can not represent LRG. Therefore, both TRG and LRG should be assessed when evaluating the response of rectal cancer to neoadjuvant CRT.