Oncological benefit of lateral pelvic lymph node dissection for rectal cancer treated without preoperative chemoradiotherapy: a multicenter retrospective study using propensity score analysis

We aimed to clarify the prognostic impact of lateral pelvic lymph node (LPN) dissection (LPND) for rectal cancer through a multicenter retrospective study using propensity score analysis. A total of 1238 patients with pathological T2-4, M0 rectal cancer who had undergone curative operation between 2007 and 2008 were examined. Majority of the patients (96 %) were treated without preoperative chemoradiotherapy (CRT). Clinical background data of the patients treated with LPND and those treated without LPND were matched using propensity scores, and hazard ratios (HRs) for cancer-specific mortality were compared. LPND was performed more frequently for lower rectal cancers and in patients with more advanced disease, and 29 % of the patients were treated with LPND. After matching background features by propensity scores, LPND did not correlate with improved cancer-specific survival (CSS) among the entire study population [HR, 0.73; 95 % confidence interval (CI) 0.41-1.31; P = 0.28]; however, LPND was correlated with significantly improved CSS in female patients (HR, 0.23; 95 % CI, 0.06-0.89; P = 0.04) but not in male patients (HR, 0.95; 95 % CI, 0.48-1.89; P = 0.89). The results were similar when patients treated with LPND finally diagnosed as pathologically negative for LPN metastasis were compared with those curatively treated without LPND. It is suggested that the prognostic impact of LPND for rectal cancer treated without CRT might be different between sexes, and LPND should be considered for female rectal cancer patients although they are diagnosed as clinically negative for LPN metastasis.