Prognostic significance of distribution of lymph node metastasis in advanced mid or low rectal cancer

Abstract

Few studies have focused on distribution of lymph node metastasis. The aim of this study is to evaluate the prognostic significance of the location of involved lymph nodes in patients with advanced mid or low rectal cancer. We defined proximal lymph node involvement (PLNp) as superior rectal and inferior mesenteric lymph node metastasis along the trunks of the supplying vessel, and mesorectal lymph node involvement (MLNp) as lymph node metastasis located within the mesorectum. PLNp was identified in 67 patients (8.4%) of total 797 patients. Age <60 years (P=0.02), poorly differentiated/mucinous histologic type (P=0.011), and positive perineural invasion (P<0.001) were risk factors of PLNp in patients with node positive rectal cancer. Patients with PLNp had poorer oncologic outcomes than those without PLNp in terms of overall survival (P<0.001). For patients with node-positive rectal cancer, there was significant difference in the overall survival rate between PLNp and MLNp groups, regardless of N stage (P=0.025 for N1, P=0.009 for N2). Our results suggest that PLNp is associated with adverse oncologic outcomes and has prognostic significance in patients with node positive mid or low rectal cancer.