Prognostic significance of lymph node yield in patients with synchronous colorectal carcinomas

The National Comprehensive Cancer Network (NCCN) guidelines recommend examination of a minimum of 12 lymph nodes (LNs) for accurate staging of a single case of colorectal cancer. However, the guidelines do not support the examination of LNs in synchronous colorectal carcinoma (SCC). This study aimed to investigate the association between lymph node yield and the prognosis of SCC patients.

Synchronous colorectal carcinoma patients were selected from the Surveillance, Epidemiology, and End Results (SEER) database over a 10-year interval (2004 to 2013). Systematic dichotomization for optimal cut-off point identification was performed using X-tile. The baseline for the two LNs groups generated was balanced using the propensity score matching (PSM) method.

A total of 4616 patients met the inclusion criteria. The cut-off number for lymph node retrieved from a single patient was 15 and 12 for the first- and second-time diagnosis of SCC, respectively. Age, T category, N category, tumor grade, tumor site, tumor size, and radiation sequence were not balanced in the two groups. After adjusting the baseline in the two groups, the same results were observed. Age, T category, N category, tumor site had a partial effect on lymph node yield. There might be some biological characteristics of the tumor that influence lymph node yield.

Retrieval of fewer than 15 LNs at the first time of SCC diagnosis indicates worse SCC prognosis. Because factors such as manner of surgical examination influence SCC prognosis, specimens should be preserved for at least 6 months to enable reevaluation should there be a need. Irb: IRB approval is not required because the SEER data are freely accessible.