Selective Lateral Pelvic Lymph Node Dissection in Patients with Advanced Low Rectal Cancer Treated with Preoperative Chemoradiotherapy Based on Pretreatment Imaging

Background. The significance of lateral pelvic lymph node (LPLN) metastasis in advanced low rectal cancer treated with preoperative chemoradiotherapy (CRT) remains unclear. The objective of this study was to evaluate the outcomes of selective LPLN dissection (LPLD) based on the pretreatment imaging in patients with advanced low rectal cancer treated with preoperative CRT. Methods. We reviewed 127 consecutive patients with clinical stage II-III low rectal cancer below the peritoneal reflection who underwent preoperative CRT and curative resection. LPLD was performed in patients with suspected LPLN metastasis based on MDCT or MRI before CRT (LPLD group, N = 38), and only total mesorectal excision (TME) was performed in patients without suspected LPLN metastasis (TME group, N = 89). Clinical characteristics and the oncological outcome were compared between groups. Results. The median tumor-to-anal verge distance was 40 mm in both groups. The median maximum long-axis LPLN diameter before CRT was 0 mm in the TME group and 10.5 mm in the LPLD group. Pathological LPLN metastasis was confirmed in 25 patients (66 %) in the LPLD group. Local recurrence at LPLN developed in 3 patients (3.4 %) in the TME group and in none (0 %) of the LPLD group. Multivariate analysis showed that only ypN was an independent prognostic factor for relapse-free survival (RFS), but LPLN metastasis was not associated with poor RFS. Conclusions. The incidence of LPLN metastasis is high even after preoperative CRT, and LPLD might improve local control and survival of patients with LPLN metastasis in advanced low rectal cancer treated with preoperative CRT.