Lymph node status as a prognostic factor after palliative resection of primary tumor for patients with metastatic colorectal cancer

Lymph node (LN) status is one of the most important predictors for M0 colorectal cancer patients. However, its clinical impact on stage IV colorectal cancer remains unclear. The study aimed to explore the prognostic value of LN status after palliative resection of primary tumor for patients with metastatic colorectal cancer (mCRC). We combined analyses of mCRC patients in Surveillance, Epidemiology and End Results (SEER) database and Fudan University Shanghai Cancer Center (FUSCC). A total of 17,553 patients with mCRC were identified in SEER database. X-tile program was adopted to identify 2 and 10 as optimal cutoff values for negative lymph node (NLN) count to divide patients into 3 subgroups of high, middle and low risk of cancer related death. N stage and NLN count were verified as independent prognostic factors in multivariate analyses of patients in whole cohort and in subgroup analyses of each N stage (P<0.05). Validation of FUSCC cohort of patients demonstrated that metastatic tumor burden (P = 0.042), NLN count (P = 0.039) and sequential chemotherapy (P = 0.040) were significant predictors of poorer CSS. Specifically, the prognosis of patients at stage N0 was significantly more favorable than that of patients at stage N2 (P = 0.038). In conclusion, primary tumor LN status was a strong predictor of CSS after palliative resection of metastatic colorectal cancer. Advanced N stage and small number of NLN were correlated with high risk of cancer related death after palliative resection of primary tumor.