The efficacy of adjuvant chemotherapy after total mesorectal excision with selective lateral pelvic node dissection for lower rectal cancer.

Abstract

50 Background: The standard strategy for lower rectal cancer (LRC) is neoadjuvant chemoradiotherapy (CRT) plus total mesorectal excision (TME) in Western countries. TME with or without lateral pelvic node dissection (LND) followed by adjuvant chemotherapy is the standard treatment for LRC in Japan. However, the efficacy of adjuvant chemotherapy for LRC after TME without LND remains unclear. The aim of this study was to assess the efficacy of adjuvant chemotherapy for LRC after TME without LND. Methods: We retrospectively reviewed patients who underwent R0 resection by TME without LND and received adjuvant chemotherapy between 2010 and 2020 at our institution. The inclusion criteria were as follows: age ≥ 20 years; histologically confirmed adenocarcinoma; pathological stage III (UICC 8th); lower rectal cancer (Ra/Rb); patients who received adjuvant chemotherapy after R0 resection without LND and no prior treatment before surgery. We evaluated relapse free survival (RFS) and overall survival (OS) in patients with LRC. Prognostic impact of location, adjuvant chemotherapy regimens, T factor, and N factor on RFS was explored by a multivariate analysis. Results: From a total of 197 patients, 117 patients were eligible. Median age was 65 years (range 26–82) and 54 patients (46%) were male. Tumor location was 67 (57%)/50 (43%) for Ra/Rb and pathologic stage was 47(40%) /61(52%)/ 9(8%) for IIIA/IIIB/IIIC. Eighty patients (68%) received fluoropyrimidine monotherapy (single agent) and 37 patients (32%) received oxaliplatin based therapy (doublet) as adjuvant chemotherapy. The 3-year RFS rate and 3-year OS rate were 70.7% (95% CI, 59.0-81.1%) and 94.5% (95% CI, 89.0-98.1%). The 3-year RFS rates according to tumor location (Ra/Rb) and adjuvant chemotherapy regimen (single agent/doublet) were 76.9%/70.7% and 71.8%/68.5%, respectively. The 3-year RFS rates based on pathological stage (IIIA/IIIB/IIIC) were 76.7%/68.4%/64.8%. In a multivariate analysis, T3/4 were identified as an independent poor prognostic factor for RFS (p<0.05). Conclusions: TME without LND followed by adjuvant chemotherapy for patients with LRC demonstrated favorable 3-year RFS rate. adjuvant chemotherapy regimens after TME without LND suggested no additive efficacy of oxaliplatin on RFS.