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. J. Surg. Oncol. 2015; 112:415–420. © 2015 Wiley Periodicals, Inc.