Improving colon cancer prognosis using Index of Metastasis: A SEER analysis

4019 Background: Survival and staging in colon cancer is related to the number of lymph nodes (LN) containing metastasis. However the total number of LN examined is variable. AJCC staging does not account for cases with few LN. Prior studies have not evaluated the index of metastasis (IM) for colon cancer using Surveillance Epidemiology and End Results (SEER) data nor the limitations of IM for prognosis. The aim of this study was to evaluate the predictive value of the IM for survival and to define the boundaries of this relationship. Methods: Patients with stage III colon cancer diagnosed 1998–2004 were identified from the SEER registry, 2007 release. 5-year cancer-related survival rates by stage at diagnosis were determined using the Kaplan-Meier method. IM was defined as # positive LN/total # LN Patients were stratified by Tstage (1–2, 3, or 4) and N-stage (1 or 2) or IM quartile according to T stage group. Log-rank analysis was used to determine the range of total LN number over which IM remained prog...