[Thirty years' changes of the strategy of lateral lymph node dissection in low rectal cancer: treatment experience and prognostic analysis of 289 cases in one single center].

The surgical indications, resection extent and management principle of lateral lymph node dissection (LLND) in lower rectal cancer have been controversial between Eastern and Western countries. This study aims to provide a theoretical basis for the rational implementation of LLND by reviewing the changes of LLND strategy over the past 30 years in a single-center, and analyzing prognostic factors for the survival outcomes of patients with lateral lymph node metastasis (LLNM). A retrospective observational study was performed. Clinical data of 289 patients with rectal cancer who received LLND at the Department of General Surgery of Peking University First Hospital from 1990 to 2019 were collected. Patients were divided into three groups based on decades. There were 89 cases in 1990-1999 group, 92 cases in the 2000-2009 group, and 108 cases in the 2010-2019 group. Data analyzed: (1) patient baseline data; (2) surgery and postoperative recovery; (3) lateral lymph node dissection; (4) postoperative survival and prognosis of patients with positive lateral lymph nodes. The surgical methods and pathological results of LLND were compared between groups, and the prognostic risk factors of patients with LLNM were analyzed. A total of 289 patients underwent radical resection with LLND' accounting for 6.3% of the 4542 patients with rectal cancer during the same period in our hospital. Except decade-by-decade increase in tumors with distance from anal verge ≤ 7 cm, the proportion of ulcerated tumors, and the proportion of neoadjuvant radiochemotherapy, the differences in other baseline data were not statistically significant among 3 decade groups (all >0.05). The proportion of LLND in the 3 groups decreased decade by decade [9.9% (89/898) vs. 8.0% (92/1154) vs. 4.3% (108/2490), χ(2)=40.159, <0.001]. The proportion of laparoscopic surgery and unilateral LLND increased, while the mean operative time, intraoperative blood loss, surgical complications above grade III and postoperative hospital stay decreased decade by decade. These 289 patients completed a total of 483 lateral dissections, including 95 cases of the unilateral dissection and 194 cases of the bilateral dissection. The proportion of LLND in the 3 groups decreased decade by decade [9.9% (89/898) vs. 8.0% (92/1154) vs. 4.3% (108/2510), <0.001]. The median number of dissected lymph nodes in the internal iliac artery and obturator regions increased (2 vs. 3 vs. 3, <0.001), but those in the common iliac and external iliac regions decreased significantly (4 vs. 3 vs. 2, =0.014). A total of 71 patients with LLNM were identified. The rate of LLNM in the 2010-2019 group was significantly higher than that in the previous two groups [37.0% (40/108) vs. 16.9% (15/89) vs. 17.4% (16/92), =0.001]. The patients with LLNM showed a poorer overall survival (OS) and disease-free survival (DFS) compared with negative lateral lymph nodes (<0.001). There were statistically significant differences in 5-year OS rate (30.9% vs. 27.2% vs. 0, =0.028) and 5-year DFS rate (28.3% vs. 16.0% vs. 0, =0.038) among patients with only internal iliac lymph node metastasis, patients with only obturator lymph node metastasis, and patients with external iliac or common iliac lymph node metastasis. Multivariate analysis of prognostic factors showed that external iliac or common iliac lymph node metastasis was an independent risk factor for OS (HR=1.649, 95%CI: 1.087-2.501) and DFS (HR=1.714, 95%CI: 1.173-2.504) in patients with LLNM (all <0.05) . The OS and DFS were not significant different in patients with LLNM among 3 decade groups. In the past decade, the proportion of LLND in rectal cancer has decreased significantly. However, LLNM rate has been significantly increased due to preoperative imaging assessments focusing on suspicious LLNM without compromising the survival. Internal iliac artery and obturator lymph nodes can be regarded as regional lymph nodes with a satisfactory prognosis after LLND. For suspected external iliac or common iliac lymph node metastasis, the significance of LLND remains to be further evaluated.