3601 Background: A minimum of 12 lymph nodes are required during colectomy to accurately stage colon cancer. Prior studies in stage II colon cancer patients demonstrate association of inadequate lymph node examination (LNE) with worse overall survival (OS). No large-scale analogous studies related to LNE have been completed in stage I colon cancer patients. We evaluated patients with stage I colon cancer to determine the association between lymph node yield and OS. Methods: We reviewed the National Cancer Database between 2004-2015 to identify patients with pathologic stage I colon cancer (pT1N0 or pT2N0) who underwent definitive surgical resection. Patients who received radiation therapy or had missing values were excluded. Clinical and demographic characteristics were analyzed. Based on LNE, patients were stratified into 4 cohorts (LNE, 0-5, 6-11, 12-19, 20+) and 2 cohorts (0-11, 12+). Univariable and multivariable analyses were performed to identify variables associated with OS. Kaplan-Meier survival curves were computed to compare the cohorts. Results: We included 81,909 patients for analyses. Median age at diagnosis was 69. A majority were female (51.1%), white (83.8%), received care in a community cancer program (59.5%), and had a Charlson-Deyo score of 0 (66.6%). Only 0.7% of patients had a margin positive resection with a 2.5cm median tumor size. Patients were similarly split between pT1 and pT2. Suboptimal LNE was noted in 27.8% of patients. Patients with LNE were distributed - 10.7% (0-5), 17.1% (6-11), 43.4% (12-19) and 28.9% (20+). Postoperative 30-day mortality was 1.9%. 521 (0.7%) received systemic therapy. Ten-year survival in patients with 0-5 LNE was 52.8% compared to 60.1% with 20+ LNE. On multivariable analyses, patients aged ≥ 69, male sex, increasing tumor size (quartile), pT2 staging and a higher Charlson-Deyo score independently predicted worse OS (p < 0.001). LNE categories were significantly associated with OS (p < 0.001) (Table). On regrouping into 0-11 and 12+ LNE groups, 0-11 LNE group predicted worse OS (HR 1.22, p < 0.001). On multivariable analysis, the above variables continued to show similar association with OS (p < 0.001). Conclusions: Our study demonstrates that lymph node yield is associated with overall survival in patients with stage 1 colon cancer undergoing surgical resection. Furthermore, patients with suboptimal lymph node yield are associated with an inferior overall survival compared to those with optimal lymph node yield. Moreover, this study finds that a large number of patients ( > 25%) continue to have suboptimal lymph node yields. Future efforts should focus on improving the lymph node yield with optimal efforts by the surgeon and pathologist. Future studies should examine the role of systemic therapy in patients with inadequate lymph node yield.[Table: see text]
High Lymph Node Yield is Related to Microsatellite Instability in Colon Cancer