To investigate the clinicopathological characteristics of lateral lymph node metastasis in middle-to-low rectal cancers, and to further evaluate the value of the characteristics of lateral lymph node metastasis in the assessment of survival prognosis.

The clinicopathological data and follow-up results of 269 patients who underwent lateral lymph node dissection (LLND) for rectal cancers from January 2012 to December 2019 in Cancer Hospital of Chinese Academy of Medical Sciences and Peking University First Hospital were retrospectively collected and analyzed. According to the postoperative pathological results, the patients were divided into the lateral lymph node positive group (n=63) and the negative group (n=206). The clinicopathological results of the two groups were compared respectively. The risk factors of 3-year OS and RFS in patients with positive lateral lymph nodes were further analyzed.

A total of 269 patients were included in the study, and the lateral lymph nodes metastasis rate was 23.4%. Tumor histopathological type (χ²=13.527, P＜0.001), depth of invasion (χ²=6.849, P=0.009), mensenteric lymph node metastasis (χ²=39.716, P＜0.001), nerve invasion (χ²=7.126, P=0.008) and lymphatic vessel invasion (χ²=5.554, P=0.018) were important factors affecting lateral lymph node metastasis. The median follow-up time was 41 months. The 5-year OS and RFS were 58.2% and 47.3% in the positive group and 89.4% and 78.51% in the negative group, respectively. Cox multivariate regression analysis showed that: mensenteric lymph node metastasis and lateral lymph node metastasis were associated with OS (HR=2.25, 95%CI=1.00~5.04, P=0.049; HR=3.11, 95% CI=1.60~6.03, P=0.001) and RFS (HR=2.76, 95% CI=1.49~5.12, P=0.001; HR=2.51, 95%CI=1.47~4.29, P=0.001). Cox multivariate regression analysis found that the location of lateral lymph node metastasis was an independent risk factor for OS (HR=4.54, 95%CI=1.64~10.90, P=0.045) and RFS (HR=3.77, 95%CI=1.93~9.35, P=0.021).

Mensenteric lymph node and lateral lymph node metastasis are independent risk factors for poor prognosis of middle-to-low rectal cancers. Patients with lateral lymph node metastasis beyond the internal iliac and obturator regions have worse prognosis and may not benefit from LLND.