481P - The correlation between tumor regression grade and retrieved lymph nodes status in locally advanced rectal cancer after neoadjuvant treatment: results from a prospective study

Abstract

A paucity of lymph nodes harvested is common in rectal cancer after neoadjuvant treatment and the significance is still uncertain. We aimed to evaluate the correlation between tumor regression grade (TRG) and retrieved lymph nodes status in patients who underwent neoadjuvant treatment followed by total mesorectal excision (TME) for locally advanced rectal cancer. From Jan 2011 to Feb 2015, complete data was available for 447 patients with rectal cancer who received neoadjuvant treatment followed by TME enrolled in FOWARC study. According to the post-operative pathologic TRG of primary lesion, patients were categorized into 4 groups, TRG 0, 1, 2 and 3.The number of harvested lymph nodes, lymph node metastasis, and extranodal tumor deposits in each group were analyzed. Of the 447 patients, 77 (17.2%) patients were TRG 0, and 143 (32.0%) patients were TRG 1. Another 156 (34.9%) and 71 (15.9%) patients were TRG 2 and TRG 3, respectively. The median retrieved lymph node counts among the 4 groups were 8, 10, 11 and 13, respectively. The harvested lymph node in better TRG groups was less than that of poor TRG group (p = 0.001). The lymph node metastasis rates of the 4 groups were 7.8%, 14.7%, 21.8% and 38.0%, respectively. The differences were statistically significant (p < 0.001). And the extranodal tumor deposits rates of the 4 groups were 3.9%, 7.7%, 16.0% and 21.1%, respectively (p = 0.002).Tabled 1ItemsTRG 0 (N = 77)TRG 1 (N = 143)TRG 2 (N = 156)TRG 3 (N = 71)PHarvested lymph nodes (median)81011130.001LN metastasis (n,%)6(7.8)21(14.7)34(21.8)27(38.3)<0.001Extranodal TD (n,%)3(3.9)11(7.7)25(16.0)15(21.1)0.002 Open table in a new tab Lymph node metastasis and extranodal tumor deposits were correlated with TRG. The paucity of lymph nodes retrieved did not infer poor oncologic outcomes in rectal cancer after neoadjuvant treatment. The number of retrieved lymph nodes should be redefined according to the pathologic response to neoadjuvant treatment. Further analysis of optimal lymph node counts in different TRG group will be performed with survival data.