The Prognostic Significance of Extramural Deposits and Extracapsular Lymph Node Invasion in Colon Cancer

BACKGROUND: The status of resected lymph nodes in colon cancer determines prognosis and further treatment. The American Joint Committee on Cancer staging system has designated extramural nodules as nonnodal disease and classified them as extensions of the T category in the sixth edition and as site-specific tumor deposits in the seventh edition. Extracapsular lymph node extension is an established poor prognostic indicator in many cancers. Its significance in colon cancer has not been extensively investigated. OBJECTIVE: This study aimed to determine the prognostic significance of extramural nodules and extracapsular lymph node extension in colon cancer. DESIGN: A pathological review of 114 stage III and 80 stage II colon cancers was undertaken to analyze for p-T stage, p-N stage (using the fifth, sixth, and seventh editions), and the size and contour of nodal and extramural deposits. Multivariate Cox regression models were used to determine the prognostic significance of clinicopathological parameters on survival estimates. RESULTS: According to the sixth and seventh editions of the guidelines, extramural deposits were present in 29% and 31% of patients with stage III colon cancer and in 5% of patients with stage II colon cancer. Extracapsular lymph node invasion was present in 68% of cases. Multivariate analysis demonstrated that lymph node ratio, extracapsular lymph node extension, and adjuvant chemotherapy were independent prognostic factors affecting 5-year disease-free survival. The same 3 variables, in addition to extramural deposits, were independent prognostic factors affecting overall survival. The presence of extramural deposits was associated with an 11% 5-year survival, and extracapsular lymph node invasion was associated with a 33% 5-year survival. CONCLUSIONS: Instead of extramural nodules being included as part of the T category or as site-specific tumor deposits, they should perhaps be classified in the metastasis category. This has major prognostic implications and may broaden the application of a number of adjuvant agents.