Lymph Node Identification Following Neoadjuvant Therapy in Rectal Cancer: A Stage-Stratified Analysis using the Surveillance, Epidemiology, and End Results (SEER)-Medicare Database

Background and Objectives: Neoadjuvant chemoradiation (nCRT) for rectal adenocarcinoma reduces lymph node (LN) identification following surgical resection. We sought to evaluate the relationship between LN identification following nCRT and disease-specific survival (DSS), stratified by pathologic stage. Methods: The SEER-Medicare database (2000-2009) was queried for 1,216 pathologic stage I-III rectal cancer patients who underwent nCRT followed by curative-intent resection. Cox regressions evaluated the association between pathologic stage and DSS for LN cut-points from >= 2 up to >= 12 LNs. Results: Extent of LN identification did not influence DSS in ypStage I or ypStage III disease; in particular, the 12 LN cut-point was not associated with DSS for ypStage I (HR 1.29, P = 0.51) or ypStage III (HR 1.08, P = 0.42) patients. In ypStage II patients, actuarial survival improved continually with increasing lymph node identification up to >= 12 LNs. The 5 LN cut-point was associated with the greatest reduction of risk of cancer death (HR 0.56, P = 0.006), with decreasing magnitudes of survival benefit associated with nodal counts beyond 5 LN. The 12 LN cut-point was not associated with DSS in ypStage II patients (HR 0.67, P = 0.07). Conclusion: The association between DSS and LN identification is a dynamic outcome that varies by pathologic stage, with unique prognostic significance for ypStage II patients. (c) 2015 Wiley Periodicals, Inc.