Impact of number of nodes retrieved on outcome in patients with rectal cancer

Purpose: We postulated that the pathologic evaluation of the lymph nodes of surgical specimens from patients with rectal cancer can have a substantial impact on time to relapse and survival. Patients and Methods: We analyzed data from 1,664 patients with T3, T4, or node-positive rectal cancer treated in a national intergroup trial of adjuv ant therapy with chemotherapy and radiation therapy. Associations between t he number of lymph nodes found by the pathologist in the surgical specimen and the time to relapse and survival outcomes were investigated. Results: Patients were divided into groups by nodal status and the correspo nding quartiles of numbers of nodes examined. The number of nodes examined was significantly associated with time to relapse and survival among patien ts who were node-negative. For the first through fourth quartiles, the 5-ye ar relapse rates were 0.37, 0.34, 0.26, and 0.19 (P = .003), and the 5-year survival rates were 0.68, 0.73, 0.72, and 0.82 (P = .02). No significant d ifferences were found by quartiles among patients determined to be node-pos itive. We propose that observed differences are primarily related to the in correct determination of nodal status in node-negative patients. Approximat ely 14 nodes need to be studied to define nodal status accurately. Conclusion: These results suggest that the pathologic assessment of lymph n odes in surgical specimens is often inaccurate and that examining greater n umber of nodes increases the likelihood of proper staging. Some patients wh o might benefit fram adjuvant therapy are misclassified as node-negative du e to incomplete sampling of lymph nodes. J Clin Oncol 19:157-163. (C) 2001 by American Society of Clinical Oncology.