Prognostic Value of Lymph Node Number and Ratio Staging System in Stage Ⅲ Rectal Cancer Following Neoadjuvant Radiochemotherapy

Objective: To compare the prognostic value of positive lymph node number (LNN) and lymph node ratio (LNR) in stage III rectal cancer following neoadjuvant radiochemotherapy. Methods: From 2008 to 2010, 99 rectal cancer cases in our hospital received neoadjuvant radiochemotherapy or radiotherapy. Radical surgery was performed after neoadjuvant therapy. LNN distinguished four stages of lymph node involvement by TNM stage system and LNR divided patients into quartiles. The prognosis value of LNN and LNR to the patients was evaluated by Kaplan-Meier method and Cox regression. We evaluated the prognosis value of LNN and LNR for those with inadequate lymph nodes (<12). Results: The patients were staged according to lymph node number (LNN=1, 2 ≤ LNN ≤ 3, 4 ≤ LNN ≤ 6 and LNN ≥ 7) and lymph node ratio (LNR<0.075, 0.075 ≤ LNR<0.15, 0.15 ≤ LNR<0.35 and LNR ≥ 0.35). 3 year overall survival rates were different among different LNN groups and different LNR groups. Multivariate analysis showed that LNR ≥ 0.15 was an independent prognostic factor of overall survival (P=0.029). 26 patients with less than 12 lymph nodes harvest were divided into four groups (LNR<0.15, 0.15 ≤ LNR<0.25, 0.25 ≤ LNR<0.50 and LNR ≥ 0.50), LNR was proved to be a better predictor of survival. 3 year overall survival rates were significant different between LNR<0.50 and LNR ≥ 0.50 (P=0.018). Conclusion: The study showed LNR was an independent prognostic factor for rectal cancer after neoadjuvant radiochemotherapy, LNR 0.15 was a cutoff point for overall survival. LNR might be a better prognostic factor than LNN, especially in patients with less than 12 lymph nodes harvest.