Establishing the optimum lymph node yield for diagnosis of stage III rectal cancer.

BACKGROUND: The optimum lymph node yield for tumour staging following surgery for rectal cancer remains controversial. This study aimed to determine the optimum number of lymph nodes needed to accurately determine stage III rectal cancer.
METHODS: Sixty-three thousand three hundred and eighty-one patients from the surveillance, epidemiology and end resulted database, who underwent surgery for rectal adenocarcinoma in 1995-2009, were included. The primary outcome was detection of stage III rectal cancer, assessed by multivariable logistic regression.
RESULTS: Each additional node examined increased the chance of stage III diagnosis by 3.9% (adjusted odds ratio 1.039, p < 0.001). Optimum histopathological stage was reached following retrieval of 18 nodes in patients treated without neoadjuvant radiotherapy (n = 49,162) and 16 nodes in those treated with neoadjuvant radiotherapy (n = 14,219). For stage I and II cancer, retrieval of a minimum of 8 and 14 nodes, respectively, was associated with optimum five-year overall survival. For stage III cancer, increasing number of positive lymph nodes and increasing lymph node ratio (>0.5) were independent negative predictors of survival; total lymph node yield did not correlate with survival.
CONCLUSIONS: Eighteen lymph nodes for those treated without neoadjuvant radiotherapy and 16 nodes for those treated with it were needed to prevent stage migration in rectal cancer. These findings provide further evidence of the importance of the technique of proctectomy and of careful pathologic assessment.