Prognostic Impact of Lateral Pelvic Node Dissection on the Survival of Patients in Low Rectal Cancer Subgroups Based on Lymph Node Size

Background: Lateral pelvic node (LPN) dissection (LPND) is considered a promising technique for treating low rectal cancer; however, there is insufficient evidence of its prognostic value. Using centrally reviewed preoperative pelvic magnetic resonance (MR) images, this study aimed to find the patient population who has benefited from LPND. Patients and Methods: MR images of patients from 69 institutes with stage II–III low rectal cancer were reviewed by experienced radiologists. Recurrence-free survival (RFS), overall survival (OS), and short-term outcomes were measured. Results: In total, 731 preoperative MR images were reviewed (excluding patients with short-axis LPN ≥ 10 mm). Of these, 322 underwent total mesorectum excision (TME) without LPND (non-LPND group), and 409 underwent TME with LPND (LPND group). Preoperative treatment was performed for 40% and 25% of patients in the non-LPND and LPND groups, respectively. The incidence of postoperative complications was higher in the LPND group (44.5%) than in the non-LPND group (33.2%; P = 0.002). Among patients with LPNs < 5 mm, OS and RFS curves were not significantly different between the groups. Among patients with LPNs ≥ 5 mm, the LPND group had significantly higher 5-year OS and RFS than the non-LPND group (OS: 81.9% versus 67.3%; RFS: 69.4% versus 51.6%). On multivariate analysis of LPN ≥ 5 mm cases, LPND was independently associated with RFS. Conclusions: Despite the high incidence of postoperative complications, this study showed the prognostic impact of LPND on low rectal cancer patients with LPNs (≥ 5 mm, < 10 mm short axis) measured by experienced radiologists.