Pathological Analysis of Lateral Lymph Nodes in Patients With Advanced Rectal Cancer After Preoperative Chemoradiotherapy.

PURPOSES: It remains unknown whether prophylactic excision of lateral pelvic lymph nodes, specifically the internal iliac and obturator lymph nodes, may be omitted after chemoradiotherapy (CRT) in rectal cancer patients without enlarged lateral lymph nodes (LLN). Therefore, we investigated the pathological outcomes of LLN dissection (LLND) for rectal cancer after preoperative CRT.  Methods: This retrospective single-center study aimed to determine whether LLND could be omitted after CRT in patients with advanced rectal cancer who had no LNN enlargement before treatment. Specifically, we evaluated the pathological positivity rate of dissected LLNs in patients who underwent LLND after CRT. Twenty-eight patients with rectal cancer who underwent LLND after preoperative CRT between April 2014 and February 2024 were included in the present study. They were stratified into the pretreatment LLN(+) (n=17) and pretreatment LLN(-) (n=11) groups based on multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI) before treatment.  Results: The short diameter of LLN before pCRT was 10 (7-22) mm in the pretreatment LLN(+) group and 5 (2-6) mm in the pretreatment LLN(-) group. Pathological LLN metastasis was confirmed in eight (47%) patients in the pretreatment LLN(+) group (95% CI 26.2-69.0) and in none in the pretreatment LLN (-) group (95% CI 0-30.0) (p=0.01).

CONCLUSION: Pathological LLN metastasis was not identified in patients without radiological enlargement before treatment. These findings suggest that prophylactic LLND after preoperative CRT might be avoidable in carefully selected rectal cancer patients.