Prognostic impact of at least 12 lymph nodes after neoadjuvant therapy in rectal cancer: A meta-analysis

BACKGROUND The number of dissected lymph nodes(LNs)in rectal cancer after neoadjuvant therapy has a controversial effect on the prognosis.AIM To investigate the prognostic impact of the number of LN dissected in rectal cancer patients after neoadjuvant therapy.METHODS We performed a systematic review and searched Pub Med,Embase(Ovid),MEDLINE(Ovid),Web of Science,and Cochrane Library from January 1,2000 until January 1,2020.Two reviewers examined all the publications independently and extracted the relevant data.Articles were eligible for inclusion if they compared the number of LNs in rectal cancer specimens resected after neoadjuvant treatment(LNs≥12 vs LNs<12).The primary endpoints were the overall survival(OS)and disease-free survival(DFS).RESULTS Nine articles were included in the meta-analyses.Statistical analysis revealed a statistically significant difference in OS[hazard ratio(HR)=0.76,95%confidence interval(CI):0.66-0.88,I2=12.2%,P=0.336],DFS(HR=0.76,95%CI:0.63-0.92,I2=68.4%,P=0.013),and distant recurrence(DR)(HR=0.63,95%CI:0.48-0.93,I2=30.5%,P=0.237)between the LNs≥12 and LNs<12 groups,but local recurrence(HR=0.67,95%CI:0.38-1.16,I2=0%,P=0.348)showed no statistical difference.Moreover,subgroup analysis of LN negative patients revealed a statistically significant difference in DFS(HR=0.67,95%CI:0.52-0.88,I2=0%,P=0.565)between the LNs≥12 and LNs<12 groups.CONCLUSION Although neoadjuvant therapy reduces LN production in rectal cancer,our data indicate that dissecting at least 12 LNs after neoadjuvant therapy may improve the patients’OS,DFS,and DR.