Impact of Tumor Location on the Efficacy of Lateral and Mesenteric Lymph Node Dissection in Patients With Rectal Cancer Treated by Upfront Surgery.

Background: The relationship between tumor location and lymphatic flow is generally known to affect the efficacy of lymph node dissection, but the specific impact in rectal cancer remains unclear. This study investigated the frequency of lymph node metastasis (LNM) and the efficacy of lymph node dissection based on tumor location. Methods: We retrospectively investigated 882 patients with rectal adenocarcinoma who underwent total mesorectal excision with lateral lymph node dissection. Tumors were categorized by primary site into Ra (from the lower edge of S2 to the peritoneal reflection, n = 95), Rb (from the peritoneal reflection to the upper edge of the anal canal, n = 713), and P (anal canal, n = 74). LNM rates and dissection efficacy were assessed at each station. The therapeutic value index (TVI) was calculated as the LNM rate multiplied by the 5-year overall survival rate. Results: LNM was observed in 447 patients (50.7%). Mesenteric LNM rates and the TVI were higher for tumors located more orally (49.5% and 43 for Ra, 46.1% and 29.7 for Rb, 43.2% and 17.6 for P), whereas lateral LNM rates and the TVI were higher for tumors located more anally (7.4% and 3.7 for Ra, 16.3% and 8 for Rb, 29.7% and 14.1 for P). Regardless of tumor location, the TVI in the lateral region was high in the distal internal iliac and obturator areas. Conclusions: Tumor location influences LNM frequency and lymph node dissection efficacy in rectal cancer. Treatment strategies should be individualized based on tumor location to improve outcomes.