Rectal Cancer Following Neoadjuvant Radiochemotherapy

The prognosis of patients with rectal cancer is generally assessed using the TNM staging system, which stages lymph node involvement according to the absolute number of involved lymph nodes. Positive lymph nodes affect the prognosis of patients. Some research has indicated that the survival of patients with positive lymph nodes is much poorer. The 7th AJCC staging system divide patients with rectal cancer into four stages (N1a, N1b, N2a, N2b) which is more accurate than the 6th staging system, suggesting patients with more positive lymph nodes have unfavorable prognosis.

TNM staging system suggests more than 12 lymph node harvest is the premise of accurate N stage. However, adequate lymph nodes could be harvested in only approximate 1/3 patients of rectal cancer. Moreover, most of the patients with positive lymph nodes receive neoadjuvant radiotherapy which will reduce the number of lymph nodes harvest. It is difficult for the patients who have received preoperative radiotherapy to get adequate lymph nodes. The reduction of lymph node harvest may decrease patients’ prognosis and may not be reflected in TNM staging system. It affects prognosis value of N stage for these patients. Some researchers are searching for a more effective indicator to evaluate the situation of lymph nodes.

The lymph node ratio (LNR), the number of metastatic lymph nodes divided by the total number of examined nodes, might be a suitable staging system. LNR doesn’t depend on the absolute number of positive lymph nodes. It treats the ratio of positive lymph node as the indicator of lymph node metastasis. Although it has many drawbacks such as different cutoff values and inconsistent pathological evaluation, researchers focus on it as a valuable prognosis indicator.

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