Improving the AJCC/TNM staging classification for colorectal cancer: The prognostic impact of tumor deposits.

4012 Background: Identification of tumor deposits (TD) currently plays a limited role in staging for colorectal cancer (CRC) other than for N1c designation. The aim of this study was to determine the prognostic impact, beyond AJCC N1c designation, of TD among primary CRC patients. Methods: Patients with stage 1 to 3 primary CRC diagnosed between 2010 and 2015 were identified from the Surveillance, Epidemiology and End Results (SEER) database. Cancer specific survival (CSS) stratified by TDs and nodal status was calculated, and Kaplan-Meier method and multivariable COX proportional hazards regression analyses were performed. Results: A total of 74,494 patients with primary CRC were identified. Mean age was 66.4 (SD+/-13.2) years, 36,988 (49.7%) were female and 40,651 (54.6%) were right-sided. TDs were present in 4,481 patients (6.0%) and 26,603 (35.7%) had lymph node metastases. The presence of TDs were significantly associated with adverse tumor characteristics including advanced pathological stage, nodal and metastasis status, higher grade and perineural invasion. Incorporating TDs into each nodal status was independently associated with worse CSS and supported reclassification of nodal status to incorporate TDs following multivariable regression analysis as outlined in the table. Following multivariable regression analysis, the proposed AJCC nodal reclassification incorporating TDs, in combination with tumor stage was a strong predictor of CSS, and also represents a new summary staging. Conclusions: TDs are an independent predictor of worse outcome in CRC. The presence of TDs have distinctly different CSS and these data support modification of the current N classification. This study proposes a reclassification of the AJCC system for CRC to incorporate TDs and informs an updated node and summary stage. [Table: see text]